[gadfam5]

On my '93 9000 CDE I have been experiencing some intermittent electrical issues. Wondering if others have had similar experiences and if so hopefully figured out a cure.I have had the car over 2 years but these things just recently started.
1. The lights in the digital clock and digital computer info readout in the instrument cluster randomly go very dim but also, just as randomly, change back to normal brightness.
2. The heater always works well when the car is first started for the day but sometimes after it has been running a while when I restart and drive it only blows cold air until I bump the temperature selector all the way up to high.
3. Occasionally, ie once a month or so, the traction control activated for no reason and the car goes into limp home mode. The ABS light comes on too. I can flutter the gas pedel to keep moving and it lasts until I shut off the car and let it sit a while. We have had snow and ice in the past week and the TCS worked properly.
I'm wondering if it is all related or all are totally unrelated and thinking it might have something to do with corroded connections or loose grounds. Any input from anyone with similar issues would be greatly appreciated.

 

[Twinsen]

1. Sounds like a faulty dimmer rheostat. It can be replaced or bypassed.

2. This can happen when the fan in the ACC's temperature sensor (located by the heated seat controls) fails. On a cold start, it reads cold so the ACC will blow hot air. When the fan fails, the sensor will become heat soaked from the vents, and heated seat controls, and the ACC will compensate by blowing cold air.

3. My guess is a failed wheel speed sensor, but you'll need more info to be sure.

 

[gadfam5]

Thanks for the input. I'll see if I can dig up a different temp sensor from my spare parts boxes. I read in other posts about the rheostat failure issue so I checked to see if the 2 lights I refer to are part of the system controlled by the rheostat. They are not as all of the other instrument panel lights are controlled by the rheostat when the lights are switched on and it has no effect on the digital clock and info lights. I don't know if it might still be related though, do you? Thanks again.

 

[Twinsen]

My diagram is showing a brown/white wire from the rheostat to:

-EDU
-Clock
-Instrument cluster
-Radio
-Misc switches

 

[Superaero]

The clock issue will be the light sensing diode failing. Thy almost all do eventually. You cn sort if test this by covering the "electric eye" with your fingertip or a piece if tape for long enough to see if the display goes dim. If it does then removing the obstruction during daylight should restore the brighter light. The instrument panel dimmer has no effect on this display as it only has the 2 settings: bright in daylight and dim at night. The other possibility is there are 2 lightbulbs illuminating that unit which might be failing. Popping the unit out would allow access to these bulbs from the back.

From your description these are all unrelated faults.

 

[gadfam5]

Thanks for the input. It sounds like the main diagnosis is a 19 year old car with 19 year old electronics systems. I have parted out a few other 9000s so i guess I can try switching out some parts. All in all though, the car runs great.
Thanks again.

 

[chengny]

The issues you describe (if they are occuring all at once and recently) are only related by overall system voltage.

The ECU will selectively disable individual systems when it senses low power.

As a check, try installing a new (or know good) battery.

 

[gadfam5]

Now that you mention it I have suspected some kind of larger electrical problem. Last spring it started not having enough juice to start up sometimes so I bought a new battery. It worked great for 4-5 months but started going dead/not holding a charge. The charging voltage readout on the dash was sometimes low but sometimes up in the 13 volt range. Sometimes it would start fine in the morning but not restart after it had been driven. I suspected some kind of electrical drain but could not find one. My son was driving it regularly and I gave him a booster box to carry but sometimes it didn't even work with that. It acted as if the voltage was not getting to the starter motor but usually after it sat for a half hour or so it would work, start up and run fine. I finally sort of gave up and figured it was a bad battery and exchanged the 6 month old battery for a new one under warranty. I also swapped out the alternator with a spare. It seemed to work great but that is when I began noticing the gremlins. I have been driving it since I switched cars with my son and he is driving my '97 9000. I notice that when I first got it back on the road about a month ago with the new battery and alternator the volt meter digital readout was consistently around 14 volts. Tonight I noticed in was low 13s. Perhaps the gremlin is something bigger than one of the small issues I originally mentioned. Any thoughts on this situation would be greatly appreciated.

 

[chengny]

My daughters 97 was having voltage fluctuations also headlights dimming. Close watch on the system voltage revealed a drop from the mid 13's down to low 12's during a H/L dim episode (2 seconds max).

I pulled the alternator (from the top!!) and inspected the brushes. Barely anything left - 2mm on the cool one and 1mm on the one next to the bearing.

Soldered in a new set ($2.50 for the pair) and she consistently runs in the low 14's now.

Maybe the brush set in your spare alternator is not any better than the original?

 

[gadfam5]

Thanks again. I had it tested before I put it in and it checked out OK but I didn't look at the brushes. I think I will put some new ones in the alternator I took out and have it ready for any future need.

 

[chengny]

Yeah, smart move. Much easier while it's on the bench.

As far as your installed unit, it is possible you know, to pull just the brush holder for inspection without removing the alternator.

It's a bit of a struggle to reach down behind the manifold but it is certainly less of a project than an alternator pull. It's even easier if you have a spare alternator to practice on.

Brushes that are nearing the end of their life can make contact 99.9 percent of the time but under load/temp changes fail to track along the sliprings properly.

A bench test (especially a static/no load test) cannot fully simulate operating conditions and so it will not always reveal that the brushes are worn past their usefulness.

 

[ryanweather]

Was there any resolution/fix to this issue? I'm experiencing the same thing. After pulling the alternator, having it tested okay, putting the alternator back in...I don't know where to go from here; or if an alternator can test okay on autozone's machine and still be faulty...

 

[gadfam5]

Sorry to say I have not figured out anything definitive or, more importantly, anything specifically to fix any of the issues and no one has come up with any specific diagnosis. Let me know if you figure anything out and I will post if I do.