Volvo 7 Series Guide

Electrical: Engine Starting, Charging
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Electrical: Engine Starting, Charging
FAQ Home
Volvo Maintenance FAQ for 7xx/9xx/90 Cars
Jump-Starting Engine Procedures
Jump Starting Alternator Procedures
Alternator & Starter Applications & Parts
Starter:
Starter and Solenoid Problems
Starter Will Not Engage: Start Inhibitor Switch
Removing Starter
Diesel Starter Fails: Wiring Fault
Alternator and Charging:
Alternator Mounting Bushings
Alternator Not Charging
Alternator Getting Weak; Regulator/Brush
Replacement
Checking Alternator Diodes
Testing Alternator/Battery Voltage
Alternator Wiring is Failing
Alternator Interchange
Battery, Terminals, and Wiring:
Slow Battery Discharge
Starting Problems and Battery Cable/Terminal
Corrosion
Unexplained Drivability Problems; Rotting Battery
Wiring Harness; Loose Connector Nut
Car Battery Failure: Diagnostics
Car Battery Replacement Tips
Battery Explosion; Wiring Chafing

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Jump-Starting Procedures. When jump-starting a car with a dead battery, the
proper procedures to ensure personal safety and car reliability are:
1. Ensure that the cars are not touching to prevent unwanted ground/earth
paths. Do not allow the cable clamps to touch each other.
2. Put out cigarettes before opening the hoods. Wear safety glasses in case a
battery explodes (more common than you would think!)
3. Turn both cars' ignitions "off".
4. Connect one end of red wire to positive (+) bad car battery terminal
5. Connect other end of red wire to positive (+) good car battery terminal
6. Connect one end of black wire to negative (-) good car battery terminal
7. Make last connection with other end of black wire to bad car engine ground
point (such as a lift metal hook) away from the battery. This eliminates
sparking near the bad battery, which may be outgassing hydrogen and could
explode. Do not attach the cable to the negative terminal of the dead
battery.
8. Start good car engine. Stand away from the batteries.
9. Start bad car engine
10. Turn on both car headlights (see below)
11. Disconnect in inverse order, being careful to keep cables and clamps from
touching.
[Tip from Paul] The book "Bosch Fuel Injection Systems" by Charles Probst notes
that after the jump and before cable removal one should put a load on the car by
turning on headlights or the rear window heater. A lightly loaded car may
experience a spike AFTER you remove the jumper cables since the regulator was
set to supply a heavy load. You instantly switched from a heavy to light load and
the voltage may spike. You may damage your fuel injection computer with this
spike. Avoid it by engaging a load.
Note: You can print these instructions out, xerox onto a plastic sheet, and mount it
near your car battery for on-site reference.

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Alternator Stops Charging: How to Get Home? My battery charging light just
came on and I am far from home. Belt is fine. What to do? [Steve] No reason to
be stranded because of this problem. You can get it home like this: Simply run a
hot wire from the battery positive and connect it to the terminal on the back of the
alternator....the one with the small red wire connected to it. This wire provides
excitation voltage for the alternator. If you can get the engine started and then
apply 12 volts to the excitation terminal, the alternator will charge. You don't even
have to connect the wire. Simply touching the jumper wire to the terminal will
cause the alternator to start charging, and remain so as long as the engine is
running. If you did connect it, you will need to disconnect it when you stop the
engine else it will drain your battery.
Alternator & Starter Applications and Parts. [Dave Stevens] Wood Auto
Supplies Ltd. in the Huddersfield, Yorkshire, UK has an excellent on-line alternator
and starter reference tool for parts. Visit http://www.woodauto.com to enter their
site. They ship worldwide. For alternators/starters, if you know the Bosch (or
Marchal or whatever) part number then enter it in the upper right search box. Each
major listing will give you the specs, a list of equivalent or similar units, the Volvo
part numbers, the years, models and engines in which it was used and a list of the
component replacement part numbers and an indication of availability. Many of
those components are linked to their own page with further information on the part
including a typically long list of all the alternators/starters in which that part was
used. If you don't have the alternator/starter number handy then you can use this
vehicle search page:
http://www.woodauto.com/woodauto/vehicle.aspx. First, make sure the upper right
search box is clear (or you'll come up empty). Select Volvo as the manufacturer
and then your particular model and/or engine. You'll then be given a list of the
alternators and starts by model year and application. You may need to try a couple
of model/engine/alternator/starter configurations to find the appropriate list of
alternators/starters. From the list just start following the hotlinks to find the full
descriptions and the parts you're interested in. Most are complete with pics. [Jay
Simkin] Contact Barsanco in Centerline, Michigan (800-421-3374) for starter and
alternator parts (diodes, etc.) to rebuild your own units.
Starter:
Starter and Solenoid Problems.
What causes a starter to fail?
[Tips from Counterman Magazine, August 01 & Underhood Service, May 04] Starter
problems can be caused by worn brushes (carbon pads inside the motor that
supply current to the rotating armature), by shorts or opens in the armature or
field coils or by worn bushings that increase drag or allow the armature shaft to
rub against the pole shoes. Continuous and prolonged cranking is very hard on a
starter because it generates excessive heat. If not allowed to cool down every 30
seconds or so for at least a couple of minutes, the starter will be damaged by
continuous cranking. Other failure modes include:

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"Zero engagement" or "no-clicking" activation of the starter solenoid. This can
be caused by an unintentional activation of a vehicle anti-theft system. In
other cases, a defective ignition switch, start inhibitor switch, or bad wiring
harness/loose wiring connection can cause the problem. The most accurate
way to test these components is to connect a DVOM to the primary wire
connection on the starter solenoid. Using the min./max. feature found on most
professional DVOMs or multimeters, record the voltage at the solenoid terminal
when turning the ignition switch to the "crank" position. If battery voltage is
recorded, the above components should be considered in good condition. If the
starter clicks, but doesn't engage, the problem is usually caused by a faulty
starter solenoid that's not engaging the starter drive gear. In most cases,
replacing starter solenoids is not a cost-effective procedure compared to
replacing the defective starter with a remanufactured unit.
Starter motor is running but fails to engage the flywheel ring gear or when the
engagement is rough and noisy. In most of these cases, the overrun or one-
way roller clutch on the starter drive gear is worn or sticking. In the remainder
of these cases, the flywheel ring gear itself is either worn, or has broken or
missing teeth.
Low-cranking speed issue caused by worn shaft bushings. The starter's
amperage draw will be unusually high for the application. Also, when starter
current draw is high, remember that battery voltage will often drop below 9.6
volts. This is enough to affect system electronics, which, in turn, will affect
fuel pump operation. Engines must crank at about 200-300 rpm to activate
the electronic fuel injection. When the ECU "sees" a strong, sustained signal
from the crankshaft position sensor, it will activate the fuel pump relay in
order to pressurize the fuel injectors. Without a reliable RPM signal indicating
sufficient cranking speed, the ECU may not activate the fuel pump relay,
thereby creating a cranking, no-start condition.
Keep in mind that simply dropping a permanent magnet starter can fracture a
field magnet, which may cause a variety of cranking speed symptoms.
Troubleshooting the Starter
In the Shop:
To accurately test a starter, you need a test stand that can measure amp load,
voltage and rpm. A good starter will normally draw 60 to 150 amps with no load on
it and up to 250 amps under load (while cranking the engine). The no load amp
draw will vary depending on the type of starter. If the amp draw is too high, the
starter needs to be replaced. The same is true if the starter doesn't achieve the
specified rpm.
Sometimes the starter motor works fine but the drive gear won't engage the ring
gear on the flywheel. If the drive gear mechanism can be replaced separately,
there's no need to replace the entire starter. A bad solenoid can also cause starter
problems. The solenoid acts like a relay to route power directly to the starter from
the battery. It may be mounted on the starter or located elsewhere in the engine
compartment and is usually connected to the positive battery cable. Corrosion, poor
ground at the solenoid mount or poor battery cable connections will prevent the
solenoid from doing its job.
If the starter tests okay but fails to crank, another possible cause may be a bad

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ignition switch, neutral safety switch or clutch safety switch. A low battery and/or
loose or corroded battery cables can also prevent the starter from cranking the
engine.
On the Car:
When troubleshooting the starter, pay close attention to the wire/cable connections.
The starter needs a healthy shot of juice to get going so you need to clean all
contacts. Just because they appear OK when the starter is not engaged doesn't
mean that they are good enough to do the job. Check ground straps. Make sure
your fuses are clean. Check any other device on the starter circuit (if any).
Make sure your battery is OK - turn your headlights, fan, rear de-mist etc. all
on and check the voltage - should be at least 11V. If it's less than 9 or so you
may not have enough power to turn the engine over.
Test the battery terminals - should be clean and tight. If your starter won't
turn I'd remove and clean them, then coat them with some Vaseline and put
back. Also test the connection between the wires and the terminals - again,
should be tight and clean. The usual symptom of loose connections here is
that the starter solenoid 'clicks' but the engine doesn't turn.
Test the + wire (the big thick one) connection on the starter. Again, this
should be a good connection. The starter draws several hundred amps, and a
connection that's not 100% is quite likely to drop most of the battery voltage
across it.
Make sure the starter is bolted to the engine properly - the current goes
through the starter and block. Also make sure the engine is grounded - it
should have a big earthing strap, or sometimes the battery - terminal is
connected directly to the block - either way, make sure the contacts are good.
If all of the above check OK, simply put a wire from the battery + to the starter -
connect it to where the thin wire goes. This should make the engine turn over (but
not start unless the ignition is on). If the engine turns, it means that you have a
problem in the wire between the ignition switch and the starter; If it doesn't, the
starter is faulty: If you don't hear a 'click' the solenoid is to blame, otherwise the
starter motor itself.
Starter Will Not Engage: Start Inhibitor Switch.
[Symptoms: I have an 89 740GL that sometimes starts but sometimes does not.
When I turn the key the car simply will not turn over: no starter response on key
to "start". However, all of the panel lights, the battery level and starter assembly
are good. When this happens I usually put the car in Neutral and then back in Park
which usually works allowing the car to start.]
[Response:] If your car is an automatic, like my wagon, make sure that the start
inhibitor switch located under gear indication panel is not out of adjustment. A
simple test is to push the selector forward or back a little in the P position (the only
one the car should start in) as you turn the key. If the car starts, crawl under and
adjust the rod just a little and the problem should be solved once and for all.
Failing this option, check the switch and wires associated with the lockout switch.

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[Response: JohnB] Took about 250K and 16 years, but there it was: a potential
pattern failure at the start inhibitor (neutral safety) switch. A nice square contact
(should be rounded and smooth--the other one was) point due to wear and a
relaxed copper alloy arm...the car wouldn't start unless the switch was compressed
by hand (a get-home crutch, BTW!). And beware...the Volvo part comes with a new
and cheaper connector that the dealer crutches by selling you four terminals and
the late model socket for an additional $5.00!! You're supposed to clip the OEM
chassis harness clip off and crimp the new male spade terminals on and install the
late model socket so the new NSS can plug into it...I just used the old socket and
spliced it onto the new NSS. This same NSS is used on the 9xx series....
Removing Starter. The top starter bolt is difficult to remove. Before you go crazy,
see the last comment in this paragraph.
Removing Without Lowering the Transmission. You need a 1/2 inch six point 18mm
socket (940; 740 may require 19mm) or a swivelling socket, a 1/2 inch universal
joint, a large breaker bar, and enough socket extensions (with one about 36"long )
to reach back underneath the car to where you can apply the proper leverage to
get a firm grip on the bolt head. Use an impact socket if you need to. The breaker
bar should be at the rear of the transmission near the crossmember. The higher the
car, the better, but I've always done it with the car sitting at jack height. And it's
always worked. Unless you are using a lot of extensions and a universal joint, you
are going to have a hard time with this bolt. Apply some penetrating oil to the bolt
before beginning. You have to get into a position to really, really get on it!
Leverage is the key: line up the socket, the uni-joint and the extensions just right,
position yourself so you can put your weight into it, then you'll hear it: CRACK! Its
not a job for half effort. The placement near the crossmember allows you room to
use the breaker bar. While there is usually no need to remove the crossmember
and lower the rear of the transmission, if you have problems place a jack under the
tranny and remove the tranny support for better access. Do NOT drop the starter,
which may fracture an internal motor magnet. Diesel starter: see the FAQ Section.
[Art Benstein] If the above fails, use a 12 inch open end wrench from the topside
along the firewall. Apply a piece of oak 1"x1" to lever against the rear engine lift
point. You only have room to loosen 1/8 of a turn at time! [Ted Yaffo] Use an
impact wrench with requisite extensions to loosen this otherwise impossible bolt.
Removing by Lowering the Transmission.[Adam Stadnick] If you put a jack under
the transmission support crossmember, remove the four bolts holding it up, and
carefully lower the transmission down a few inches (being careful not to smash the
distributor cap if it's a head-mounted distributor) it greatly opens up the access to
the infamous upper starter bolt. I was able to remove it using 3/8" drive tools
without a breaker bar or torch or anything. I spent about an hour trying to fight
that bolt and never even got a tool to seat on it, but as soon as I lowered the
transmission it took about ten minutes start to finish.
Diesel Starter Fails: Wiring Fault.
[Inquiry:] I own a 1986 Volvo 740 Diesel. The mechanics have replaced the starter
six times from March 1999 to July 1999. The starter itself is still under warranty,
but each time I have to pay the installation labor, besides the headache of being
stranded, towing, etc. I'm not a mechanic, but even I know that something is
wrong, wrong, wrong. Does anyone have any ideas? Even a list of possibilities that

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I could have the mechanics check-out.
[Response: Van Audekerce Remi/Brandon] I have seen this quite a few times and it
was always a short in the wiring harness that engages the starter when the engine
is running. Most likely the place were the wires have rotted is where the wiring
harness runs near the diesel pump. Cut the black sleeve open and check the wiring,
most likely the wire insulation will fall apart. Check ground connections, the wiring
harness, and battery condition. With a diesel starter requiring 2 kilowatts that
comes out to 250 amps at 8.0 volts cranking. Any slight resistance will slow things
down in a hurry.
[Noel DeSouza]In my case, the grounding wire going from the battery to the
engine was bad, so check the obvious first. Use one side of a battery jumper wire
clamped so as to ground the starter body (the head of the starter-bolt is a good
spot to clamp) and the other side clamped to the negative post of the battery, then
try starting again. If it turns over, the ground wire or connections are bad.
Alternator and Charging:
Alternator Mounting Bushings. [Editor] Over time, the three rubber bushings
securing your alternator in its engine bracket can compress, allowing the pulley to
become misaligned with the crank pulley and accelerating belt noise and wear. You
can replace these with OEM rubber bushings or aftermarket polyurethane, which
are more robust and do not compress as easily. The latter may be had from IPD.
To replace your bushings:
Disconnect battery negative terminal
Use penetrant oil to loosen the tension adjusting, securing, and bracket nuts
but don't soak the belt
Unscrew the 10mm tensioner adjusting bolt beneath the side of the alternator
by about 1.5 cm. Remove the belt from the pulley.
Loosen the 12mm bottom securing nut and remove it from the adjusting
assembly
Loosen the top long bolt and nut (12 & 13mm) supporting the alternator in its
bracket
Remove the bottom nut and bolt (12 & 13mm) holding the alternator to the
bracket
Swing the alternator up. Using a screwdriver, push out the old bottom bushing
and replace it
Swing the alternator back down and replace the bottom bracket bolt and nut
Remove the top long bolt and nut and swing the alternator back to replace the
two top bushings
Replace the top bolt and nut and the securing nut
Tighten the bracket nuts (not the securing nut!) and retension the alternator
belt so you can press it down about 1/4 inch under moderate finger pressure
Once you tension it, tighten the securing nut firmly and then back off the
adjusting bolt so it bears no tension from the belt
Reconnect the battery negative terminal
If you are interested in replacing the four air conditioning compressor bushings, see
the FAQ file.

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Alternator Not Charging. When the battery loses charge and the alternator
appears not to be charging, here are some diagnostic tips:
Diagnostics. [Response: Danny Halamish] It sounds like it's probably the charging
system. Here's what I would check (in this order):
Battery terminals - clean? Good connection? Corrosion?
Alternator (thick) wires - both plus and ground (if fitted) - make sure they are
OK.
Alternator brushes - if they are nearly dead, this can cause this.
Harmonic Balancer: the alternator belt runs off the balancer. If the rubber
insert deteriorates, the balancer shell will slip
If all that checks out OK, I would suggest you get a volt meter, and when the
voltage reads a little low, measure at the alternator: It should be 14.4V. If it's
much less, rev it up a little - does the voltage go up? If not, there is a problem.
Also, with the engine running and the voltage low (i.e. when the problem happens)
measure the following:
1. Voltage between the alternator power terminal and the battery + terminal
should be well under 0.2V
2. Voltage between the alternator body and the battery "-" terminal should be
well under 0.2V
3. Voltage between the battery "-" terminal and the engine
block should be well under 02.V
Voltage Regulator. If all this checks out but you still have a
problem, the alternator voltage regulator may be defective. There
are two screws holding it into your alternator. You don't even need to pull the
alternator. Remove it and you'll probably find the two brushes (two black square
spring loaded shafts) worn out. A good electrical shop can replace these, or a new
regulato rfor either Bosch or Nippon Denso alternators is about $60. Install and,
get a boost and happy motoring.
[Testing Bosch voltage regulator on 7xx/9xx cars: How can you tell if your voltage
regulator has gone bad?. What tests can you do?
[Answer:] The real purpose behind the regulator is to keep the battery voltage
from getting too high. When my regulator went bad, voltage would increase with
engine speed, going as high as 18-20 V. You can easily test the regulator function
by using a voltmeter to test voltage between your battery and ground while the car
is running. Look for voltage between 13.8 and 14.6. If your voltage is higher than
this, you probably do have a bad regulator. Check the integrity of the regulator
diodes on a Bosch alternator by using a multimeter to measure the voltage
readings at the D+ terminal and B+ terminal. The voltage reading should be the
same at both terminals. A difference of more than one volt would indicate faulty
diodes and the need to replace the regulator unit. [Rick Ledbetter] Test the diodes
by disconnecting one of the D+ or B+ leads on the regulator and connecting your
probes: black is ground (use the alternator case for ground) and red is touched to
the D+ and B+ terminals. At the component level, diodes will only conduct one
way. They have to be tested out of circuit, so one lead has to be disconnected from

Electrical: Engine Starting, Charging
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the circuit. A simple continuity test on the meter will do the job. If you have a
failure, the Bosch regulator/brush pack unit is easy to replace with the alternator in
the car. If your battery has been overcharging, it can boil off electrolyte and may
need to be topped off.
Exciter Current Through the Warning Lamp on the Panel. The alternator
(charging) warning light in the instrument cluster feeds a small amount of electrical
current to the field coils in the alternator when you turn the key on and the engine
isn't turning. This excites the coils (electromagnet) and the alternator gets the
magnetic field it needs to start charging as soon as the engine runs. When the
alternator isn't charging at all (engine stopped) that wire to the alternator also
provides a ground path for certain warning bulbs in the cluster, so they light up.
Diodes in the network keep current from backfeeding into unwanted circuits. So if
you have a bad connection for the alternator warning wire, the alternator won't
start charging right away. But most alternators will self-excite once the revs get
high enough (say 2000 engine RPM) and then they stay excited and charging, even
at idle RPM.
[Editor] To initiate charging upon startup, the small wire going into the rear of the
voltage regulator must be at 12 volts. If this is grounded or disconnected (as, for
example, through a loose instrument panel or chassis connector), your alternator
will not charge. The idiot lights may or may not go on, but if they do and they
remain on, then suspect this wire or the panel connector for faults. You can also
rarely experience a flexible circuit board failure on the back of the panel. And make
sure the alternator warning lamp bulb is not burned out.
[John Randstrom] If you pull the wire off the alternator that comes from the dash
board charging lamp and ground it, the idiot light should light with the ignition in
the run position. If the lamp does not light then there is a problem with the bulb,
the ignition switch, or the wiring/instrument cluster circuit. An easy way to see if
this circuit is causing your no charge situation would be to connect a wire from the
battery positive terminal through a small spare idiot light bulb(or any bulb with the
same wattage and voltage specification) to the idiot lamp circuit connector on the
alternator. The alternator should charge and the lamp should light when the engine
is off, and go out when the alt. starts charging just like the original dash lamp
should do.
[Tip from Paul Golden] I removed my instrument cluster and did the continuity
checks, sure enough the solder joints had come loose from the wiring. I fired up
the soldering iorn and hit each solder joint with some fresh 50/50 flux core solder.
Installed the instument panel and presto, all the lights work once again. Since then
I have repaired that same problem in 6 different cars, 760, 3-960, 2-940 so it
seems to be a regular problem.
Diagnosing Alternator Exciter Circuit Troubles. [Bruce Young] The Battery,
parking brake, brake warning, and bulb failure lamps should all iluminate when the
ignition switch applies battery +12 to one side of all 4 bulbs and the other side
finds a path to ground via that small red exciter wire from the panel to:
1. alternator D+ terminal, then
2. voltage regulator, then
3. alternator brushes and slip rings, then

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4. alternator frame, then
5. Blue wire to engine ground.
These bulbs supply the required pre-excitation current to begin alternator charging:
Battery light
Parking Brake
Brake Warning
Bulb Failure
You can test for power to and thru the bulbs to the alternator D+ terminal by
taking the red wire off the D+ terminal and holding it to any engine metal (not
the alternator itself) while a helper turns the Key ON and observes the warning
lights.
Lights ON? = all is well to and thru the D+ wire
No lights = check for battery voltage at disconnected red wire end
+12V present? = battery=>cluster=>D+ wire path OK (problem is in #1 thru
#5)
No +12V = problem between battery and +12V side of cluster circuit
Installing a Replacement Exciter Circuit to the Alternator. Is it possible - and
if so, is it wise - to run a wire from the battery's + terminal to the back of the
alternator? Or, does that create a risk of damage in the long-term"? [Steve] This
information relates to my experience with the Denso 100 Amp alternator which is
on both my wife and son's 940.
It may or may not apply to other model alternators. It's possible, but not wise to
make a hard connection from the battery positive to the excitaton circuit on the
alternator. You would only do this if the circuit on the back of the flexible
instrument cluster PCB failed.
The reason(s) are:
1. You wouldn't have the convenience of a charge light to tell you that your
alternator is charging.
2. The excitation circuit (originating in the instrument cluster and going directly to
the alternator via the small red wire) powers directly to the internal voltage
regulator.
This allows the charge light to illuminate. The voltage regulator provides a circuit to
ground to excite the alternator field windings until the alternator begins charging.
After the alternator begins charging, the voltage regulator opens this circuit and the
alternator continues to provide its own field (excitation) voltage. If you connect a
wire directly from battery positive to the alternator excitation terminal, you will
have a constant drain of the battery, and probably damage the voltage regulator
over time.
On my son's 940, I did run a separate wire to the excitation terminal but not from
the battery. I ran this wire from a "switched hot" source under the dash and on to
the alternator. Inside the car, I pulled a loop of this wire out of the dashboard, cut
it, and soldered a light bulb holder for a standard 1034 12V light bulb into the
circuit. The hot wire is soldered to the terminal next to the center contact on the
bulb. This did three things: it gave me a "idiot light" to tell me if the alternator