Experts Needed For Phantom Problem

i AM THE NOT SO PROUD OWNER OF A 94 LESABRE. AS IN A PERVIOUS THREAD I WAS HAVING TRANNY PROBLEMS I THOUGHT. NOW IT SEEMS AFTER STARTING CAR EARLY ONE MOURNING LIGHTS, AS WELL AS HEATER SURGED. EACH TIME THERE WAS A SURGE THE TRANS. WOULD DROP OUT OF GEAR. AFTER PARKING CAR IN SHOP AND INVESTIGATING THE PROBLEM, I FOUND THAT EVERYTHING WAS SURGING. I AHVE CHANGED BATTTERY, ALTERNATER, CHECHED ALL THE GROUNDS, EVERYTHING. WHEN ENGINE IS RUNNING, LIGHTS DIM, GET BRIGHT,FAN SPEED AND SLOWS, AND TRANS GOES IN AND OUT OF GEAR. A REPUTABLE GM MECHANIC SAYS IT MIGHT BE AN IGNITION SWITH PROBLEM YET I BEG TO DIFFER. YOU CAN HEAR THE ALT. LOAD AND UNLOAD IN A REPITIOUSE CYCLE. IF YOU TAKE THE BATTERY CABLE OFF THE ALT. THE PROBLEM SEEMS TO STOP, YET YOU CAN'T DRIVE FAR WITH IT DISCONNECTED. ANY HELP WOULD BE GRATLY APPRECIATED. OH BY THE WAY---NO CODES, HISTORY, OR ANYTHING SHOWS ON COMPUTER. MAYBE JUST A REALLY BAD COMPUTER--IT IS A RENAUFACTRED ONE I FOUND OUT. IF NAY ONE CAN HELP IT WOULD BE NICE. LEAVE REPLY HERE OR E-MAIL ME AT ELCBOSS@AOL.COM. HELP PLEASE WIFE IS WEARING OUT MY TRUCK WHILE CAR IS DOWN. THANKS

Basics here, what does a voltmeter on the alternator say when this happens, proper engine ground, battery to chassis and/or engine grounds.

IF YOU TAKE THE BATTERY CABLE OFF THE ALT. THE PROBLEM SEEMS TO STOP, YET YOU CAN'T DRIVE FAR WITH IT DISCONNECTED. THANKS
NEVER disconnect the battery cables while the engine is running, or run the engine with the cables disconnected! This is no longer a viable way to test alternators and will ruin many of the versions that are in use today.

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i AM THE NOT SO PROUD OWNER OF A 94 LESABRE. AS IN A PERVIOUS THREAD I WAS HAVING TRANNY PROBLEMS I THOUGHT. NOW IT SEEMS AFTER STARTING CAR EARLY ONE MOURNING LIGHTS, AS WELL AS HEATER SURGED. EACH TIME THERE WAS A SURGE THE TRANS. WOULD DROP OUT OF GEAR. AFTER PARKING CAR IN SHOP AND INVESTIGATING THE PROBLEM, I FOUND THAT EVERYTHING WAS SURGING. I AHVE CHANGED THANKS

Have you completely checked the ground cable and positive cables inside the plastic for corrosion of the copper? Check the whole cable. You said you've replaced the battery.

I assume you cleaned the contact ends really well.

Yes, I have cleaned all cables, inspected--traced out grounds, ran extra ones the where problem might be and so one. Like i stated---when engine is running, with lights on fan blowing, evertything surges. You can even hear tranny making funny noise as if engaging and disengaging. anyway voltmetr connected to battery-engine running voltage surges from 11.6 to 14.2. the one thing i did and it probably wasn't wise was to remove the charge wire to battery and it will stop. seems i am back to searching more intensely. will try and bypass ign switch next to see if maybe breaking contact inside before replacing either it or computer. (oh by the way it is a reman) must have been changed before purchase. Thanks
Larry.
Texas

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Check the 12V power cable going to the under-hood fuse/relay center on the firewall. Take the cable loose & clean the mounting surface and both sides of the terminal. Do you have ACC (Auto Climate Control)? If so, disconnect the electrical terminals at the blower control module. It is located on top of the fan box, below the under-hood fuse/relay center. You will need to remove the two 10 mm nuts that secure the fuse/relay panel to the firewall and pull it forward, to access the module wiring. It should have two plug-in terminals. With those removed, take it for a drive and see if the electrical surging is still there. I have seen a failing or failed, blower control module, cause the symptoms you described on several occasions.

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Thanks for the hint. Not only had I tried cleaning the cable ends, when remembering what you said, I decided to check the voltage on the charge wire to the alt., and needless to say is was crazy. With that not being correct and car still acting crazy I decide to check it at the relay panel on the fire wall and yes you were exactly right. Not only shoud you just clean the ends of the cable, cut all the rubber of and lo and behold a problem. Corrosion under the rubber and inside the cable. Reworked the ends, started engine and eveything works great. Amazing isn't it how a computer code never should low voltage and they don't work well without it either. Thanks for all your help. I will try and pass this info along to other with simular problems.
Larry
Texas

Problem I thought resolved, still there. As I stated earlier, the main problem has gone, yet part of it still remains. Though the corroded cable had a lot to do with it, I still have the surging in the alternator, lights will get bright and then dim. Could the bad voltage problem to the main fuse and relays have caused the computer to go bad and not show a code. When this problem happens, and the aternator either loads or unlaods the trans. will disengage for a breif moment. Any help would be appreciated---I am my wits end. Thanks:banghead:

I'd replace that cable.

First to know the alternator either is lowering down the current or the car is. You said the car runs fine without the cable to the alternator, at least for a while (till the battery dies). This iliminates the car electronics. If it runs fine till the battery gets too low so less worry there.

When the resistance is high across that bad cable the alternator is thinking its provided enough current. A loose connector may ruin the alternator or make it sick.

A varying alternator current is caused either by electrical load change (cable), belt slip, or internal alternator problems.

The ECM has nothing to do with controling the voltage from the actual alternator but uses what it gets from alternator/battery system.

The transmission is controlled by the electronics in the transmission and the ECM tells it when to shift, so you cant depend on it to function properly with varying voltages and suspect that problem will go away with the fix.

When the car is idling there usually isnt enough current produced to the system to keep up the voltage and you may see a varying voltage at low RPM.

A voltage check at a cigarette lighter would see a 12v battery, then a 13.8v alternator.


The cable from the alternator or the alternator itself is suspect. Replace the wire or duplicate another to the battery, paralell it.
The alternator did take alot of heat and hits.

You might try AAA auto parts there in Littlefield.. a used alternator may save some $$ or if you just got it you may can swap it out at the store or even have it load tested.


Bass

Thanks for the help all you people out there. Persistance pays off in the long run. After going to our GM dealer and visiting with a lot of differant folks, I had in my possesion the manual for the car. Now then with some time on my hands I started checking wires for corrosion, loose connections, etc. Upon finally tracing the feed wire form fuse panel,through instrument cluster by color and circuit number in the gm manual I finally came to the pcm. Now get this---computers don't tell on each other. No scanner or the big one at the daelership showed what I found. The voltage to b-1 on red connector with car running fairly steady with engine running. Now then the b-4 coonector was really out of whack. voltage that feeds alternator The exciter wire varied from 3 to maybe 11 volts. Yep--there was my problem. Replace pcm and car runs smooth as glas once again and no surging, trans locking up and relasing due to bad voltages. I will always remeber this and hope my problem will help someone else down the road. Thanks again guys.

larry
texas

Not only shoud you just clean the ends of the cable, cut all the rubber of and lo and behold a problem. Corrosion under the rubber and inside the cable. Reworked the ends, started engine and eveything works great.

Which cable did you find the corrosion in? The power cable at the relay center or at the battery end?

The exciter wire to the alternator...
I believe the red wires are to the alternator..

I cant see a B1 and B4.. connection reference anywhere on my schematics at the alternator though. Perhaps the PCM is where he checked the voltage and the fix was at the alternator.

Sorry I should have stated what i found more clear. On the red connector at the pcm brown or b-1 is feed to pcm for charging. Red or b-4 output to alternator. PCM was the culprit. good voltage in and bad out. Electronic alternators seem to be a bit differant than what i am accustomed to dealing with. Thanks again

Larry
Texas