Odd Electrical Problem

My 1995 RMS has a perplexing problem. While driving down the road it the motor would briefly stop. The lights on the dash would come on just like when you turn on the ignition to start the car. The speedometer would dip way down. The car would then start back up, the speedometer would overshoot and then settle down, and all would be fine. The whole incident would only last for a second or two. I also noticed that the cruise control was finicky and sometimes wouldn't work at all. Using the turn signal made the speedometer fluctuate. Sometimes the car would stall while in a parking lot.

I replaced the turn signal switch and it helped some. I then cleaned the plug in and all seemed well. The cruise control now works flawlessly and the above ended. However, the other day the car started normally but soon died. All electrical stuff was dead, interior lights, chimes, etc. I hooked up the battery charger and the battery showed 85%. The car had no response at first but then fired up. It soon died. This was repeated a few times and then it ran fine for a 250 mile round trip except for dying once in a parking lot as I slowed to a stop.

Today I took it to the shop. They tested the battery, alternator, and starter and all was normal. All of the connections were fine.

It seems fine except that there is the occasional blip on the speedometer needle.

Any ideas?

Thanks,

Check your grounds. It could be almost any of them. There are two on the A pillar under the hood release. Check the one at the battery to the fender too. Any others that you see.

I think its your auxiliary post up on the firewall by the relay baox,.

phantom 309 wrote:

I think its your auxiliary post up on the firewall by the relay baox,.

Today after work it wouldn't register her first turn of the key but it started with the second. The clock was way off suggesting an electrical disconnection.

Nick would you mind posting a picture of what you described.

Thanks,

I got tired of looking for a pic,..

pass side inner fender,.

black relay box,.
beside it covered with a rubber cap thingy,.

its a post,. one of you three battery cables goes to it,.

originals are zinc,. corrode easy get hot under load etc,.

brass one is the replacement,.

Next time the car won't do anything,. take a booster cable go from positive battery post jump to that post,.
it supplies power to the interior of the car,.

just search up" B-body auxiliary battery post",.

phantom 309 wrote:

I got tired of looking for a pic,..

pass side inner fender,.

black relay box,.
beside it covered with a rubber cap thingy,.

its a post,. one of you three battery cables goes to it,.

originals are zinc,. corrode easy get hot under load etc,.

brass one is the replacement,.

Next time the car won't do anything,. take a booster cable go from positive battery post jump to that post,.
it supplies power to the interior of the car,.

just search up" B-body auxiliary battery post",.

Thank you Nick. I was able to find and print the TSB and also found a brass post kit on eBay. I'm going to take both to the local Chevy dealership and see if they will fix it.

Here is some info:

http://www.impalassforum.com/vBulletin/showthread.php?t=237690

http://www.rmsautoparts.com/images/94c59.pdf

This dealership is amazing. They told me once that they needed to replace two parts whose combined cost was almost $400. They recommended that I buy the parts elsewhere and bring them to them as I would save a bunch of money. I found them for $60. Amazing.

Thanks again!

Thats unusual for a shop in my area. Nice break!

The auxiliary battery post has been replaced. One problem remains. The fuel pressure is normal but drops down enough to kill the car when you step on the brake. Any ideas?

Thanks

need a better description,. is it a sudden decrease in speed?

or you are stopped and idling and touch the brake , and as soon as the brake lights come on, it quits?

phantom 309 wrote:

need a better description,. is it a sudden decrease in speed?

or you are stopped and idling and touch the brake , and as soon as the brake lights come on, it quits?

The latter. If you are stopped and idling it quits as soon as you touch the brakes. It is getting so bad that once started you need to give it gas to keep it running. Then when you touch the brake so that you can shift from park to drive it quits.

Thanks

So,. just to be clear here,. it starts and idles fine,.
it drives fine,..

So if you were to very lightly touch the brake pedal just enough to activate the brake lights but not really apply the brakes,.it will quit running while idling in park,..
leave the brake pedal alone and the car will idle smoothly for as long as you want,..

Have i got it right?

Sort of. It was like that. Then it deteriorated to where it would start right up but then soon die if you didn't give it gas. That is when I took it to the dealership. They replaced the aux. battery post in accord with the TSB and noted that the post was shot but that the associated buses were ok. They noticed that the fuel pressure dropped upon touching the break pedal.

Today I got an update that it quit doing it and it is behaving fine. They have one older mechanic who has years of experience who was out this week but will be back on Monday. He will look it over then before they release it as they can't understand why it is behaving now and they want to be sure that it is ok.

This is a conundrum.

Well again all signs point to the aux post,. it supplies the power for just about everything in the car,.

the factoy battery cable is like an octopus,.has three cables all formed to one,.

of the three,..
the shorty goes to the alternator
the medium goes to battery post,
The long to the starter,.

The symptoms you describe really seem to me like that cable is suspect,.

I mentioned before,. jump from either battery positive to the aux stud
or alternator to aux stud,

Your symptoms remind me of trying to move a car with no battery in it,.
boosting the car, then removing the battery when it starts, if the alternator and regulator are good it will usually keep running on the alternator power, but can just quit when you step on the brakes as the regulator isn't quick enough to keep up with the sudden draw in power,.
I usually turn on the headlights to keep the alternator at a high charge rate when doing this,.

So if i was in your position, i,d also see if the car runs fine with the headlights turned on,.

Thank you very much Nick. Do you think that the aux post getting too hot damaged the cable?

Thanks again,

I would inspect the grounds. If a poor ground is shared between multiple circuits, one circuit can sometimes find a false ground through the others. But when power is applied to the circuit providing the false ground, it brings the voltage up too high at the ground. (A classic example is the behaviour of trailer lights when the ground is inadequate -- eg: turn signals work until the tail lights are turned on).

I'm not sure exactly how grounds are wired on the sedans, but if the fuel pump and brake/tail lights are wired to a common body ground screw it could explain things.

Thank you everyone for your help. Replacement of the battery cables seems to have been the final fix.

The aux battery post problem is a whopper. The old one was shot. The original owners put 40k on the car during its first two years, then only 14 k in the next 18. I don't think that they ran it long enough for the problem to surface.

Interesting as I thought only the 94s got the zinc posts, and 95 and later were all brass.

Was your bad one brass or zinc (gold or silver)? Maybe really early 95s got a zinc one...just curious.

Mine was zinc. It was made in 1994