I'm having a really frustrating electrical problem. It seems to have started a few days after installing some 90/100 watt (90 w low beam) H4 headlights. They burned out my dimmer switch, but I bypassed that. Anyways, now when I'm driving (even without headlights), my car will stall because my voltage is dropping.

The car is fine for about the first 30 minutes or so, then it will start missing a few beats, then catch and run for a few minutes. This goes on and on until the stalling gets more and more frequent and lasts longer. Eventually I have to pull over to the side of the road because my car won't run. My power windows won't work, and when I measure the voltage at the battery it goes as low as 8 volts. I have to sit and wait for a while before I can drive my car again.

What could this be? I'm thinking it is something that is heating up and has to cool down before the car can run again. Would this be consistant with the circuit breaker going bad? If it's going to 8 volts at the battery though, that sounds like a short, right?

Rob

 

It sounds like you need to replace the dimmer switch and put your headlights on a relay. Ron Francis Wire Works makes a "bright lights" kit to do this. I'm thinking you may also have cooked your alternator along the way. Without it, the battery will eventually drop like yours is, but it will recover some after the car sits and run again.

 

I forgot to mention that I changed the alternator. I had an old rebuilt unit, so I figured that may have been shorting, so I installed a new 100 amp Tuff Stuff alternator. Didn't help ;(

I would like to install that kit though. Thanks for the heads up!

Rob

 

I'm beginning to think that some of you people don't LIKE trying to diagnose electrical problems! But then I think that I'm just being silly.

Rob

 

hehe electrical problems are rly annoying....I had a problem similar to yours lately. The problem was the cable going to the starter...I think there's a fuse in there that was overheating cause of my headers. Took me a while to figure out as I thought it wouldn't affect me after the car was started....I was wrong. It was making my car stall all of a sudden and all power was going out...only thing that had power left were the headlights. power would go back on after a while...at first it wasn't that bad...but it became worse until I couldn't even do a mile before it stalled again for 30mins. I hope this helps.

 

Lohkay you are awesome, that sounds exactly like my problem. Where is the fuse? Is it the small cable that goes through the engine compartment? (starter - alternator I think)? Is it the large battery cable?

Rob

 

Are you sure your alternator drive belt tension is adjusted correctly? I read that you replaced alternator recently so this was a thought. Or, maybe the replacement alternator is bad or your regulator. Replacing the headlamps has nothing to do with a interior light dimmer ! :lol:

 

Sounds like a grounding problem, loose belt, or bad alternator. These are all good things to check. You might make sure the frame to block ground cable is good as well as the battery to frame.

A bad belt will do this too. Slip just enough to slow the alternator down where it won't generate enough juice.

Check all of the headlight ground wires as well.

Electrical problems are a pain, because they usually have a simple cure, but require overturning almost every stone to find the simple cure. One problem can cause several symptoms.

 

Hehe I almost forgot to check back on this thread....I didn't do the work myself...The garage guy told me it was the fuse link to the starter. Now I don't think its the battery cable but the other wire that goes there... Its as much as I can help you. Sorry. :(

 

Well thanks everyone for the responses! It is not the alternator as it exhibited the exact same symptons with the old and now the new alternator (new as in brand new not rebuilt) - also because the problem happens when the engine is not running as well (the power windows won't work with the motor off until it 'cools down' or whatever).

Fred - I meant the headlight dimmer switch (hi/lo switch), not the guage dimmer switch ;)

OK Lohkay I figured that is what you meant (the fusible link on the ~10 guage red wire going into the interior), so I swapped that out today. The largest fusible link the store had was 14 gauge and my car did the same thing (stalled) after about 2 minutes of driving. I am going to either bypass the fusible link or try to find a larger one. Right now the car is stalled in a parking lot in Chicago. I hope that is it, but there is only one way to find out.

UGH I HATE ELECTRICAL PROBLEMS. Especially intermittent problems that pop up while you are driving.

Thanks everyone for the help!

Rob

 

I sure hope its that...keep us informed!

 

Rob,

How long do you drive before it stalls out. Are we talking long enough for the engine compartment to heat up or just a quick down the block thing? Check the block where the wiring out of the alternator and the rest of the system comes together, on the '74 this is on the drivers side wheel well just in front of the windshield washer bottle.

My next guess is the fusable link, but it sounds like you've been down that road. Next check the wiring off of the starter, check carefully around the header area. Finally check to make sure the battery cable connections are tight and clean.

What is the ammeter showing?

I might have some free time this weekend, can you limp out to Oak Park? If so we can run thru some diagnostics here at my garage.

Drop me a line,
-harry


[Modified by Harry74, 11:09 PM 8/15/2001]

 

UGH it is not the fusible link. I completely bypassed it (with an intention of re-adding one of course), and it did not fix it (or even help it). What I did though - is ran a wire from the starter to the passenger compartment, and one from the ignition @ distributor to the passenger compartment. When it stalled I tried both on the multimeter - and I got 12-12.5v @ starter and 0-50mv @ distributor. Oddly enough I found that when I slammed the door sometimes it would instantly pick back up to 12v @ the ignition, then I could start the car and drive it for about 10 feet before it would stall again.

Harry - I now don't think it is heat related. Before it always ran for a while before stalling, so I figured was heat related. Now, it stalls right after starting it. Yesterday I went to the garage and it was cold and it wouldn't start. So my heat-related theory is out the window. Unfortunately the ammeter is disconnected (I am going to try to reconnect it, but I hate to monkey with a lot of things at the same time). There is no way I could make it to Oak Park on it's own power now :( I can barely limp around the block. I had to literally hop 10 feet or so at a time to the garage last night.

I have a large Lectric Limited schematic sheet (I recommend these! They sell them for each year, one large 20"x30" laminated page with the whole car wiring diagram. I think it was $7). Anyways, it looks like a wire goes from the starter (10 guage red) through the wiring harness to the alternator. Then it goes into the harness to the dash and to the ignition switch. From here it goes out to power the guages/ignition (which all fail). So I am going to have to hack into the wiring entering the igntion switch to see if I am losing voltage BEFORE the switch (I think I am).

Where is the fusible link between the alternator - ignition switch ? That could be it I think. Now a fusible link will break inside the wire but if you wiggle the wire around you could still connect it momentarily I think so that could explain why it works when I slam the hood/door.

Rob

 

haaaa.... :( Sorry to hear that rob. It really seemed like the same problem I had. I wish you luck!

 

Rob,

Check the wiring harness where it goes into the firewall ( from the engine compartment side), try wiggling the connection, they usually never come loose, but this is a vette we are talking about and the fact that slamming the door helps really makes it sound like a loose connection.

Let me know if you don't get it by this weekend, I can come out by your place and give you a hand, tow sets of eyes/hands always makes electrical trouble shooting easier.

-harry

oops: In answer to your question, I believe the fusable link in the charging system is located right near that connection block I was talking about on the inside of the wheelwell, look for a somewhat fat wire.




[Modified by Harry74, 5:28 PM 8/16/2001]

 

If you recently replaced and engine or engine mount, check to see if the block to ground strap is still there.

 

FIXED! I was playing with the wires where they go into the firewall like Harry described, and watching a multimeter on the ignition. When I was pulling the wires I saw the multimeter jump between 0 - 12. I got in there and tested all the fusible links (to see if one was blown and just barely connecting in the sleeve - BTW there are like 3 fusible links right at the firewall) the all checked out good! So I got under the steering column (oh one of my favorite places on a c3, espeically with an aftermarket alarm), and I noticed by tugging on the wires the multimeter was going all over the place. ANYWAYS it turns out that it was one of the plastic plugs (like 5 wires go in, it plugs into a female counterpart atop the steering column). It was loose! That was it! I just pushed it in and it worked. WHAT A PAIN for one stupid little thing. At any rate, I'm glad it's done!

Thanks everyone for the help and bearing with me on this! Harry I appreciate the offer of you to drive out by me, that's really nice. I'll have to show you the car one of these days with the new exhaust. I got pictures that I need to develop and scan for anyone else interested.

Thanks again ppl and I'm glad this thread can end!

Rob