help--voltage drop!!
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Senior Member
Joined: Sep 2002
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From: Louisiana
help--voltage drop!!
ok--mine is a completely stock 86 GXL. I noticed this week that when driving, the voltmeter will sometimes drop--normally reads about 14 but will drop to just over 12 for just a second then go back up. It only does it while driving....cant get it to do that while sitting at idle or when the engine is off. Still have enough juice to run everything, but I am concerned about this--where should I look to fix this? The alternator has been recently replaced with a reman one, and the battery is less than a year old. Any ideas would be a huge help!!
Locust of the apocalypse
Joined: Apr 2003
Posts: 2,553
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From: Directly above the center of the earth (York, PA)
If it didn't do it before you changed your altenator.,,, have your altenator checked...
Check your negative battery post for corrosion and tightness, Everytime I would hit the brakes two weeks ago, everything would dim in the car and the voltmeter would drop below 12 (I have a 3rd gen altenator, not supposed to happen). I founf the problem to be a corroded negative terminal and post.. Cleaned the post, replaced the terminal.. no problem!!!
Check your negative battery post for corrosion and tightness, Everytime I would hit the brakes two weeks ago, everything would dim in the car and the voltmeter would drop below 12 (I have a 3rd gen altenator, not supposed to happen). I founf the problem to be a corroded negative terminal and post.. Cleaned the post, replaced the terminal.. no problem!!!
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Joined: Sep 2002
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From: Louisiana
the cables and battery are all new....also--it happens wne I am driving--I can hold the gas pedal constant and be cruising, and it will happen, not cuz of hitting brakes or turning on accessories.....it happens day and night. doesnt seem to affect the performance of anything but I still wanna fix it. Also I am still getting that 3800 rpm hesitation in all gears....hafta find the time to check that out too
Do the engine ground upgrade and make sure the other grounds are good. This may help with the voltage and 3800 problems. Check for a good connection at the alt. You might have a bad connector/wire.
Also, I just replaced my coolant hoses and while doing that I cleaned and lubed the BAC valve. Sprayed a little "Carb and Choke" cleaner in it along with some WD40, then hooked it up to the battery to work the solenoid a few times. Then sprayed it clean. I didn't expect much, but I hardly notice any 3800 hesitation anymore. Might have something to do with it, might be coincidence, or it could be my 6th ports or secondary injectors decided to quit working all of a sudden (I don't feel a loss of power, so I doubt that happened).
Also, I just replaced my coolant hoses and while doing that I cleaned and lubed the BAC valve. Sprayed a little "Carb and Choke" cleaner in it along with some WD40, then hooked it up to the battery to work the solenoid a few times. Then sprayed it clean. I didn't expect much, but I hardly notice any 3800 hesitation anymore. Might have something to do with it, might be coincidence, or it could be my 6th ports or secondary injectors decided to quit working all of a sudden (I don't feel a loss of power, so I doubt that happened).
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HAILERS
Joined: May 2001
Posts: 20,563
Likes: 27
From: FORT WORTH, TEXAS,USA
Take a good look at the feed cable AT the alternator. Take it off and examine the ring terminal to see if it's good, then reconnect it and try again. In the future if the voltage drops....leave the engine running and wiggle that cable at the alternator and see if the voltage changes for good or bad. Talking about the large cable on the alternator, not the small connector with two wires.
Lives on the Forum
Joined: Feb 2001
Posts: 26,664
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From: n
Is your car totally stock or does it have a big stereo?
To me it's normal. I see my alternator drop to a scary 10.5 volts (VDO voltmeter) when idling with the headlights and AC on. I do run an RB double pulley, which is slightly underdriven.
-Ted
To me it's normal. I see my alternator drop to a scary 10.5 volts (VDO voltmeter) when idling with the headlights and AC on. I do run an RB double pulley, which is slightly underdriven.
-Ted
Refined Valley Dude
Joined: Oct 2001
Posts: 2,283
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From: Kitchener, Ontario (Hamilton's armpit)
Originally posted by Amur_
I got a little happy with ground wires on my NA FC, both help my alternator and to chase the 3800 stumble (which I finally did eliminate.)
Using 6-gauge automotive wire (make sure it's the multi-strand automotive wire - don't use anything else - and don't use anything smaller than 10 gauge) I installed a ground wire:
1) from the negative battery terminal to the chasis (the outer bolt holding the master fuse block in place on front of the strut tower.)
2) from the alternator's tension adjusting bolt to the battery's negative terminal.
3) to replace the ground wire on the backside of the engine (running from the tranny housing to a nut up by the wiper motor.)
4) on the ECU harness in the passenger footwell. But this was a 3800 stumble fix and may not be for you. I don't have the desc. in front of me but a write-up does appear in a few FAQs out there... Also added a ground at the air boost sensor for the 3800 fix (which was what finally nixed it.)
5) to replace the main engine ground (from behind the plugs/under the oil filter to the chassis.)
6) from the y-pipe (where your exhaust splits to go out to your mufflers) to the chassis. There's supposed to be a factory ground there, but 15 years on the road tends to nuke them.
You might consider adding grounding straps to the back of your car, too. I haven't, but that's because I'm willing to forgoe whatever the benefit is rather than sport attachments that I think look retarded. I don't have tassels on my coat and I'll be damned if I'll have any on my rotary rocket.
Make sure that all your connections are clean. Scrape away paint and remove any dirt or oil. Use an external tooth washer between each connector and the surface, if you can. And tighten the hell out of it. Use a spray-on enamel on all the ground points to inihibit corrosion (if they start to rust they won't be as effective - my boost-sensor ground started to corrode not long after I put it in - I first noticed it when the stubmle started re-appearing! I cleaned it up and she's been fine ever since.)
I got a little happy with ground wires on my NA FC, both help my alternator and to chase the 3800 stumble (which I finally did eliminate.)
Using 6-gauge automotive wire (make sure it's the multi-strand automotive wire - don't use anything else - and don't use anything smaller than 10 gauge) I installed a ground wire:
1) from the negative battery terminal to the chasis (the outer bolt holding the master fuse block in place on front of the strut tower.)
2) from the alternator's tension adjusting bolt to the battery's negative terminal.
3) to replace the ground wire on the backside of the engine (running from the tranny housing to a nut up by the wiper motor.)
4) on the ECU harness in the passenger footwell. But this was a 3800 stumble fix and may not be for you. I don't have the desc. in front of me but a write-up does appear in a few FAQs out there... Also added a ground at the air boost sensor for the 3800 fix (which was what finally nixed it.)
5) to replace the main engine ground (from behind the plugs/under the oil filter to the chassis.)
6) from the y-pipe (where your exhaust splits to go out to your mufflers) to the chassis. There's supposed to be a factory ground there, but 15 years on the road tends to nuke them.
You might consider adding grounding straps to the back of your car, too. I haven't, but that's because I'm willing to forgoe whatever the benefit is rather than sport attachments that I think look retarded. I don't have tassels on my coat and I'll be damned if I'll have any on my rotary rocket.
Make sure that all your connections are clean. Scrape away paint and remove any dirt or oil. Use an external tooth washer between each connector and the surface, if you can. And tighten the hell out of it. Use a spray-on enamel on all the ground points to inihibit corrosion (if they start to rust they won't be as effective - my boost-sensor ground started to corrode not long after I put it in - I first noticed it when the stubmle started re-appearing! I cleaned it up and she's been fine ever since.)
Also add a 6-gauge wire from the positive post on your alternator to the positive post on the battery. It will not harm anything.
Thread Starter
Senior Member
Joined: Sep 2002
Posts: 613
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From: Louisiana
thanks for the replies all....keep em coming!
First, the wire at the alt is good. connection is clean and wire is in good condition.....still hafta wiggle it around but will do that today.
Also, there is an aftermarket stereo but NO amps or subs. Far as I can tell it isnt causing the prob--I even disconnected it entirely and the problem persists. Other than that there are no mods at all to the car.
I tried to locate the engine ground behind the IM.....was looking for a strap but all I found was a single black wire(I think that is the one from the tranny housing). I added a 4 ga. strap from one of the mounting bolts for the IM to the firewall, but it didnt fix anything. Gonna clean the BAC today to get rid of the hesitation at 3800 hopefully, and thanks Amur for the grounding tips. Will give those a shot and see what happens!!
First, the wire at the alt is good. connection is clean and wire is in good condition.....still hafta wiggle it around but will do that today.
Also, there is an aftermarket stereo but NO amps or subs. Far as I can tell it isnt causing the prob--I even disconnected it entirely and the problem persists. Other than that there are no mods at all to the car.
I tried to locate the engine ground behind the IM.....was looking for a strap but all I found was a single black wire(I think that is the one from the tranny housing). I added a 4 ga. strap from one of the mounting bolts for the IM to the firewall, but it didnt fix anything. Gonna clean the BAC today to get rid of the hesitation at 3800 hopefully, and thanks Amur for the grounding tips. Will give those a shot and see what happens!!
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 27
From: FORT WORTH, TEXAS,USA
The negative cable from your battery goes from there to a bolt about a foot below the left hand strut tower. That place should give you a chassis ground. From there it continues to the long bolt on the starter. That should give you a good engine ground. Battery....chassis....engine. What more could a guy want in life.
The delivery cable from the alternator goes to the fuse box in the engine bay, then to the battery. Check the connection at the fuse box.
The best bet is to carry a volt meter with you. When the volts drop, leave the engine running and put the meter on the ALTERNATOR output. If the reading is good.....then its the delivery cable to the fuse box/battery/ and or a poor connector at the end of the cable.
The delivery cable from the alternator goes to the fuse box in the engine bay, then to the battery. Check the connection at the fuse box.
The best bet is to carry a volt meter with you. When the volts drop, leave the engine running and put the meter on the ALTERNATOR output. If the reading is good.....then its the delivery cable to the fuse box/battery/ and or a poor connector at the end of the cable.
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