Electrical Glitch... It just won't run

OK here's one for the electrical gurus.

my '71 GS will start fine and runs great in park. But when you touch the brake pedal.. turn on the fan blower.. headlights... anything electrical... the engine dies immediately.

After two weeks of checking wiring, my GEN light has come on. Took the two year old Alternator to a parts store and had it checked after checking it myself with a multimeter. They said it is bad when put under a load. Just as I figured since I was getting a reading of 11 volts at the hot wire on the back of the alternator and at the battery when running. 12 volts at battery when not running.

Bought a new one and charged the battery to full. Started it this evening... same thing. The GEN light is still on. The battery still shows 12 volts when not running.

The battery was replaced last fall because it was bad. Haven't had the battery tested yet. That's next. This battery doesn't have but about 10 hours of run time on it.

Could the external regulator be the culprit? I have no idea how to test this. It is the original I believe. The car will run with this unplugged. How does this work... and is it needed? I am running petronics in the stock distributor.

I put a nitrous system on it last fall (haven't tried it yet) so I upgraded the fuel pump to an electric holley blue pump along with 1/2" aluminum hardline from the tank to the carb/nitrous plate. This is wired through the fuse block. Thinking of wiring this straight to the battery with a fusable link/relay between them. I have another new blue pump and I am thinking about swapping them out.

I can't find any wiring problems yet. Anyone have any ideas? I run this same pump on my '57 chevy and have never encountered this problem before.

If I run the car with the pump off, sometimes it dies when using something electrical, sometimes it doesn't.

This problem didn't surface until going to the electric fuel pump.

Any suggestions would be appreciated.

 

71 GS electrical gremlins

My first question . . . have you replaced the resistor wire that originally came in the wiring harness that supplied the points controlled coil. If you have upgraded coils with the Pertronics set up you have marginal voltage to charge that coil. Therefore any other electrical glitch will make the car stall.

There are two fusible links on the battery terminal at the starter. One of them has the alternator output wired into that circuit. The fusible link offers a high voltage drop at high currents, therefore should be avoided for high current applications such as an electric fan or electric fuel pump. Your idea of running directly off the alternator output would be a good idea.

The voltage regulator is suspect if the alternator output is low. They are adjustable, but if the output is that low, I would replace it. May be time to wire in a higher output 10SI or 12SI internally regulated alternator with an 8 gage wire hooked to the big connector at the starter.

Hope this helps

 

When a car dies under an electrical load, it is usually b/c of too low voltage at the coil in order to keep running. You have full voltage at your battery since you charged it.........therefore, there must be a poor contact somewhere that won't allow high current to pass through from an added accessory. This could be a bad ground, or battery cable. You can verify this with a voltmeter connected to the circuit that is going dead............it must be done under a load, and measure voltage drop across the wire..........that is one lead to each end of of the wire. It should read near 0 volts under a load, do this on your battery cables first. Then branch out to other heavy guage wires, and don't forget about the engine ground straps. :bglasses:

 

Also to check if it's power to the coil, you could run a jumper straight to the battery from the coil.

 

I had a similar problem in that I couldn't get my car to turn off unless I activated an electrical switch with the key off. And then once the car was off and sitting for a few hours the gen light would just come on by itself eventually killing the battery in the morning. After several alternaots and voltage regulators it finally started behaving right. So I never did fully figure out the problem but I thought my two cents might offer some incite.

Allen

 

My suspicion is a grounding issue. Try this... with the engine running, check the battery voltage at several places. Put the red lead on the battery positive position and check several grounds, comparing the readings to the battery negative post. If they vary by more than .4 volts, a ground is likely the issue. Check the frame, fenders, engine etc, comparing the readings to the battery negative. You might also try checking between the battery lead on the alternator and the frame. You should see 12-15 volts. Let me know what you find. Ray

 

I had a 71 Cutlass that used to do the same thing when the little ground wire from the battery to the body would come off. It fell off several times before I fixed it right.

 

I put the red lead on the battery positive position and check several grounds, comparing the readings to the battery negative post. (IE. Frame, fenderwell, engine grounding strap, engine block ect.)

After checking this with my meter I found no discrepancies. All measurements are the same.

I also tried checking between the battery lead on the alternator and the frame. I am getting 12 volts here whether the car is running or not. I took this new alternator back to the parts store and they tested it. They said it was putting out about 14 volts.

I also hooked the electric fuel pump up directly to the back of the alternator to take the load off of the fuse block. It didn't help either.

I am wondering if it is the external regulator. How can this be tested/adjusted? After some research on this board I am leaning toward replacing the alternator again with a 12si Delco with an internal regulator. I think I am just requiring too much juice for the stock alternator with the external regulator. My current alternator's clocking position is 12. I think the 3 postion would move my wiring away from the valve covers quite nicely. Would you go with the 78 amp or the 94 amp version? I don't think I want to go with the one wire installation.

The only other electrical change I have made to the car was to install one of those Custom USA Radios to make it look a little more BUICK than the K-Mart special that was in it when I got the car.

Here's something else that might be worth mentioning... the negative battery cable is attached to the engine with a bolt through the aluminum alternator bracket instead of it being attached to the frame of the car itself.

I am getting 12 volts at the coil when the ignition switch is in the start position and 8 volts when the engine is running. I believe this is the way it should be. Correct me if I am wrong.

 

The only way to be certain of grounding is to ground the heavy negetive cable to the engine block...........run a wire from neg. to the frame to the body and back to the engine block. Make sure the contact area is CLEAN. If your problem goes away you just fixed it. :bglasses:

 

Works Great

I just finished the changeover to the 12si 94amp internally regulated alternator. This conversion was extremely easy. It sure makes the firewall look a little better, even though the fuel regulator and fram racing filter is still there.

Everything works great! I turned on every accessory I could find and the gen light never came on. and the alt is putting out 14 volts. I think this problem had been mounting since last fall.

I guess the end verdict was the external regulator was bad. I exposed all the wiring from the firewall to the starter. That in itself was a real job. Now the hard part will be harnessing/taping it all back up.

Thanks for all your suggestions. Here's a cold one for all of your help!:beer

Now that it's running good I can finally test that nitrous kit I hooked up last fall!p

 

One more thing I have a question about.... While uncovering all this wiring I found a flat plug similar to the one used on this new 12si alternator. It has two female prongs and the wires that go into it are pink and pink/black stripe. It has a diode (resistor?) wired between the two wires at the plug. It has 14 volts on both sides of the car when the engine is running.

Any ideas what this is?

According to my diagram this is for a kickdown. Is this supposed to be hooked up to the turbo 350 transmission? Or is this something for a turbo 400 trans that is used with a 455?

 

Larry my GS is the same color as the one in your avitar. At least for now. Going to black this fall (hopefully), as long as the '57 holds together this race season. I saw a GS last week while on the road that was this color too. This one was quite "PIMPED UP" and ran really bad. Complete with the hubcaps that keep spinning once the car is stopped. It smoked and I think most of the exhaust was rotted off. I only wish I would have been driving mine to show him what a car like this is supposed to look and sound like. LOL . Of course he was driving his, while mine was down for the count in the garage. To each his own I guess. Several of my buddies have seen this running around town too and keep suggesting I get those awesome wheel covers for mine.... NOT!

You are absolutely correct. I remember this now. It was right on the back of the intake.

Thanks for jogging my memory. I'll definitely remove it.

This is definitely not a concourse vehicle. Just something to cruise in (rice killer) and take to the track when my other car is down.

Just an update .... I took the car out for a drive today and put it through it's paces. The charging system is working perfectly. By the way, that annoying electrical pulsing in the lights is gone now too!

The car once again runs superb!:3gears:

 

Thar's GREAT Ryan.... but how's it drive with NOS??:Brow: o No:

:3gears: :grin:

 

GS Collector said in an earlier post:

If your are still using points to control your spark this is fine. If you have upgraded to an HEI or similar set up to Pertronics then you need to change out the resistor wire to provide a full 12 volts to the coil when the engine is running.

There is an "S" terminal on the starter solenoid wired to the coil that bypasses the resistor wire when the starter in engaged and the voltage is slightly lower.

The previous owner had not changed out the resistor wire when he installed a Mallory Unilite system on Shari's GS, and it did not work well at all.

 

I will check out the voltage at the coil since I got the charging system changed out.

When I upgraded to petronics, it said to leave the ballast resistor in place.?.?.

I will definitely change this if it is wrong though.

I haven't got the nitrous tank filled yet. I will do that this week and let you know how it does. Everything I have read, tells me that it should take a 1 to 1 1/2 seconds off of my 1/4 time.

I hope so, I would love to get this down at or under 12 seconds.

 

I am pleased that the 12SI conversion went well. I would have suggested the 94 amp, especially since the extra current is not used unless the demand is there. For those of you still using the 10DN alternator, the way to test the regulator follows. After starting the engine, short the F and #3 wire. This will "full field" the alternator. You will have no control over the output, and the alternator should "wail." Revving the engine GENTLY should raise the voltage of a good unit to over 16 volts. Be careful as this can fry anything electrical but it will isolate the alternator from the regulator, allowing the regulator to be tested. Don't worry; this procedure was used throughout the time before the computer, and still is used whenever a pre-computer vehicle is tested. It is part of the test procedures used in the factory manual. It is called "full fielding," and is utilized by all manufacturers. The 12SI is tested by grounding the tab in the alternator regulator window.
The procedure is different, the process the same. Ray

 

P.S. the short is applied to the connector between F and #3 after disconnecting from the regulator itself. Ray

 

Diagram

Hi there, im having sum lighting troubles with my 1971 Skylark Custom. The gremlin got to the headlights first, then the interior lights. Now the fuse box section that controls those two things is no longer powered. I guess there must have been a short, cuz my headlamps (all four) went out at the same time, and now they will not light even when fed power. Long story short, i need a WIRING DIAGRAM! i have been unable to find it anywhere, and itw ould really help me solve this, and a few other problems. Could you plz advise where i can get one? Thanks.
Azeem