Turbo17

I recently replaced the odometer gear to fix the common odometer failure problem. As part of that repair, while the instrument panel and all gauges were out, I checked all the indicator bulbs. They were all fine. A few days later (now) I noticed that the voltmeter says 11.6 volts, and I checked that with a voltmeter on the battery with the engine running. It was correct. I'm not getting charge voltage out of the alternator.

Normally, I would suspect the alternator/ voltage regulator/ diode bridge as being the suspect. The alternator is quite old. However .....

Doing some research I found that the "alternator indicator bulb" on the dash is used as a tickler to excite the alternator in some 944 designs. Supposedly, if the alternator indicator bulb is dead, the alternator can't start up. Does this apply to the '86 951? Is it possible I killed a bulb while removing them and testing them - and that is the source of my problem?

I'm not sure where the alternator bulb is. Next stop will be the manual to see if I can identify the location of that bulb. I checked carefully when I turned the key on before starting and did not see any indicator bulb light near the voltmeter. Is that where it's located? Or does this not apply to my vehicle? I don't have a circuit diagram for the '86 turbo - I can only find the diagram for the '88 turbo, which has been correct for everything so far. (I haven't checked it yet.)

I don't mind pulling out the alternator, but it's suspicious that I was working on the indicator bulbs and some posts say they can cause the alternator to stop charging.

If it is the alternator, I'd like to rebuild it. I've seen voltage regs and bearings for sale. Any recommendations on rebuilding? Sources for parts or parts to stay away from? Any help would be appreciated.

Thanks!

Supachink

The alternator bulb is underneath the battery / oil pressure dial. you have to actually remove the gauge from the cluster to get to the buib. You should be able to see the connection points on the back side of the cluster and hit it with a 9v battery and some test leads to see if it lights up.

does the light come on (red light at the bottom portion of the voltage gauge on the right side) when you have key on engine off? is the light still on key on engine on? if so, its probably a broken exciter wire, small gauge blue wire running from the alternator to the small white connector (one red wire one blue wire) above the brake booster. If the light does not illuminate, test for 12V on the blue wire with key on engine off.

Another possibility could be the factory alarm system. I believe that if you jump pin 1 and 4 it will over ride the alarm, but you must also jump pin 7 and 8 to provide the 12V signal to the blue exciter wire. (Clarks has a diagram on his site, but dont follow the shape of the connector he has as an image, follow the wire color pinout diagram, i chased a no charge condition for 6 months because i followed the shape of the connector)

Does the alternator begin to charge if you blip the throttle past 3-3.5k rpm?

I believe the Van did a full rebuild with bearings and regulator and created a thread or DIY for it, search for Van Alternator rebuild.

Turbo17

There is a light that turns on (key on engine off) under the oil pressure gauge. I get working warning lights on: brake pads, brake fluid, oil pressure,seat belts, and the master caution. No other bulbs light up.

Yes, I had it entirely out to do the odometer. I was worried I might have broken a wire on the flexible film circuit board back there, or possibly not connected up the 3 connectors fully.

No. There is no light on the voltage gauge. There is one on the oil pressure gauge.

If you are asking about a light at the voltage gauge, there isn't one.

Hmmm. Are you saying that there should be 12V at the blue wire with the light out? Will fixing that light (getting 12V to the light or replacing the light if it's bad) solve the issue?

It has a disabled alarm system, but that hasn't changed. It's not factory.

I'll check on the way home.

Thanks for the help - I really appreciate it.

Do you think the work done in removing the panel gauges and replacing bulbs , etc. (I did this twice - once to check the bad odometer gear and once to install it) is related to my no charge problem? Should I pull the dash again, make sure I didn't damage the film circuit board and make sure that the connectors are seated correctly? I recall seeing a lot of small indicator lights - more than seemed to light up in the test of bulbs that lit up - as listed above.

Supachink

I dont think that the work removing the gauge broke any traces unless you were trying to manhandle the cluster in. . . The odometer gear is part of the Speedo gauge, the gauge that houses the volt meter is on the far right, and it has the bulb under the face of the gauge and not accessible from the back of the complete gauge pod. If the light isnt coming on with key on engine off, it is most likely the bulb.

there should be 12v at the blue wire with the key on engine off position.

Does you 86 have a spare key hole on the fender behind the drivers door? If so you have a factory alarm unit which has a control box by the DME's. Often corroded battery boxes leak water in to this area and cause problems with the DME or the Central Alarm Control Unit. . . this is where the jumpers for pin 1 and 4 and 7 and 8 come in to play to bypass that.

I would start with removing the cluster, remove the gauges from the housing by taking off the 9 or 10 screws around the edge, then remove the voltage meter / oil pressure meter gauge, it should have two oblong shaped black washer/backing things with a brass nut in the center. remove the brass nuts and the gauge should be able to separate from the rest of the cluster backing... there will be two small bulbs in black housings on the cluster backing that illuminate the area for the oil pressure light and the battery light. The battery light is the one on the right, you must remove the entire black housing and bulb together, there are tangs on the legs, so i usually push it to one side to release the tang and wobble it the other way to get the other tang out. replace this bulb, put it all back together and turn the key on... if the light lights up, start the car, and it should charge. I literally just went through this yesterday and found that I had wired up my alarm override incorrectly. . . If you still dont have it by tonight, ill shoot some pictrues of my spare cluster to help you out.

Turbo17

Okay, more info from a test drive at lunch. First I confirmed no light below the voltage gauge with key on and engine off. Then I started and revved the engine. I did notice an increased voltage right as the revs hit about 3500 RPM. It went from about 11.8 to 12.5 volts. I did it several times and each time saw that change. Then while tooling along the highway, I downshifted to third and rocketed along, then checked the voltage, and suddenly it was up to 13.3 - 13.5 volts, which is about where it usually sits when charging.

I ran for a few miles, came to a stop and then turned on the ignition, not starting, and the light below the voltage gauge was on! So I think, it's working again.

I came back from lunch 1/2 hour later and checked again. This time the light was off before starting. I started and revved, and the voltage initially was at 11.8, but twitched up to above 12 when revs hit 3500 or so. On the highway return, I again tried high RPMs and I could get the voltage up above 12, but not to 13. When I stopped, the light would not come on with the key on/engine off test.

I tried wiggling wires behind the dash, but nothing changed.

So the bulb works, or at least it did briefly. I don't have factory alarm/key. It's a third party alarm.

I have the circuit diagram for the '88, but I think it's close to my '86 - it matched up when I checked out the lighting (I was thinking of going to LED lighting). I think I need to check the power that goes to that light. If it's not sending power to that light, I work backwards. If it is sending power to the light, then the break is at the light (intermittent filament/contact) or beyond.

I'm comfortable pulling out the gauge cluster - I've done it several times recently (and was very careful), but if you know the power feed to the light and where I can check that, before pulling the gauge cluster, it would save me some time. Is it at the "blue wire" you referred to? If there's power there (key on engine off) does that mean there should be power at the light?

Supachink

If you bulb is good, then it should be the wire. the blip of the motor to 3.5k rpm will excite the alternator which is what leads to charging. The blue exciter wire, when working properly, will do this 'exciting' on its own.

The way the bulb works is that one side is connected to a switched source of 12+v. The other side is connected to the internal regulator on the alternator. When the alternator isn't charging, current flowing through the lamp will find ground through the field coil, which is what establishes the bootstrap magnetic field. But once the alternator is charging, the lamp will "see" 12v on both leads. Since the difference in potential is zero, the bulb goes out.

The blue wire should have 12v with key on engine off. often times the blue wire breaks inside the sleeve, if you go to the white connector (with the blue and red wire) that is by the brake booster, you can test continuity from the pin on the plug there to the lug on the alternator to check if you have a broken wire. also test the other side of the connector to see if you have 12v there with key on engine off. If you have power there and no continuity its the wire, run another length of wire, fish it through the sleeve if you would like or zip tie it on the outside and try to see if it charges that way.

Supachink

Also, you stated that when you gave it 3.5k rpm that it jumped from 11.8 to 12.5. did the voltage stay there when you let off the revs or do they fall back down to 11.8? If they fall back down to 11.8 i would suspect the alternator itself, probably the voltage regulator on it having worn brushes. Replacement is ~20$ last time i checked and its only two screws on the back of the alternator.

Turbo17

@Supachink:
Thanks for the comments. It did not stay at voltage after the RPM blip. I strongly suspect worn brushes/bad voltage regulator. The regulator varies from $25 to $55 at the sources I've found, and I'm going to replace it. Do you recall if the two screws holding it on can be accessed without removing the alternator? Or do I have to pull it first?

Supachink

I think you can get in there with a stubby screwdriver if you have an AC delete and no alt shroud. forget what it looks like in that area without the ac compressor in the way. . . but at the point of AC delete, the alternator is quick and easy to pull off

Turbo17

Mine is a daily driver and the wife wants me to fix the A/C - which hasn't worked for 15 years. I need to pull the A/C compressor anyway to inspect it. I just ordered the VR from Amazon. A Hella at $18. I'll pull the alternator to inspect it.

I checked the voltage at the blue wire. It was around 10.5 volts engine off and key on.

Thanks for the help. I'll let you know how it goes.

Turbo17

Here is the update:

The alternator brushes were worn out and not making contact after 180K miles. It had nothing to do with my odometer repair. Just coincidence.

The rings were in excellent shape - there were no deep grooves. I cleaned and polished the rings anyway, then replaced the brushes/voltage regulator.

The bearings seemed fine. I know I could pull them out, but I'll leave that job for another time.

Although Clark's says you have to drain the coolant to remove the alternator, I didn't have to. The only problem is pulling out the main long bolt that holds the alternator on. I found there was just enough room to slip the head of that long bolt past the coolant hose if I squeezed that hose as I pulled out the bolt.

The cap over the back of the alternator (for cooling air) is a pain to get to - particularly the bottom nut, but I needed to remove the A/C compressor anyway, which made it easier.

lee101315

To save time, disconnect that two wire harness by the brake booster and give the blue one power from the battery. If it charges, your problem is in the cluster. If it doesn't, you'll need a new voltage regulator or an alternator.

It would have saved you the trouble of removing the cluster. By the way, usually by the time the brushes wear out, the contacts on the commuter have too. Your repair should work for a few thousand miles, maybe more.

rraulston

OH MY GOD!!! 3 months of trying to figure this out and I come across this thread. It WAS my alarm bypass!! I, too, followed the shape of the connector and screwed myself!!! I did as you suggested and followed the wire colors and it fixed it!!!! I so owe you a Beer and Pizza!!!!

mahoney944

I noticed that my oil pressure indicator light is always dim compared to the alternator indicator light when i turn the key on engine off. if the bulb for the alternator can cause voltage issues are there any concerns with the oil pressure bulb? possible faulty readings?