atkinsom

This just started happening where I noticed the gen and brake lights come on bright at WOT and then dim and disappear. It may have been coming on before lightly but I didn't notice. I did a voltage test across the battery with the car at idle speed with nothing on and got 14.95 at start and then it stabilized around 14.69 -14.80 jumping around a bit in the process. I did a voltage test on the battery after turning off the car and it read 13.14 and started to drop slowly.

I also checked the belts and they're tight with no slipping as I replaced them last year. I haven't done load tests on the battery yet as I'm waiting for my brother to bring the tester. Any other ideas that might cause this only at WOT. Thanks

1969 Cutlass S
2bl 350ci
Turbo 350 trans

MDchanic

Is your engine ground strap intact, clean, and connected?

- Eric

atkinsom

I'll check the engine ground strap tomorrow along with the ground that comes from the negative battery terminal that attaches to the side of the radiator assembly...there's also a ground wire at drivers side inner fender panel I believe that runs just above the battery that I'll check. Weird that the lights come on only at WOT and then dim and disappear

Rickman48

Unless the gen. light is connected to the kickdown switch??

atkinsom

It's a turbo 350 tranny so the kickdown is mechanical I believe...although there is a kickdown switch on the throttle pedal but is disconnected. Going to check the grounds later today as per the suggestion above.
Does the engine ground strap sit on the back of the right cylinder head and go to the firewall?
Could a battery with a bad cell cause this condition where the gen and batt lights come on only at WOT?

MDchanic

Yes.

You mentioned a wire from the battery to the core support.
As long as there is a good, clean, heavy connection between the engine and the body, or between the negative battery terminal and the body, you're good.
The problem is if the engine is well grounded, but there's no ground connection to the rest of the car.


No.

- Eric

atkinsom

Here's another thought after reading like crazy. Could a bad voltage regulator that sits on the firewall cause the lights to come on at WOT only since there's a surge of power at that time?

MDchanic

Not something I've ever heard of, and I don't see a way it could be possible

- Eric

atkinsom

I checked this morning before work for the engine ground strap and didn't see one but based on the ground cable from the negative terminal going to the core support I should be good based on your post Eric. Any other thoughts on potential issues besides disconnecting grounds, cleaning and reconnecting? Thanks again for the suggestions.

MDchanic

No. This is really weird.

Based on the description, though, of two unrelated lights coming on at wide open throttle only, the most logical explanation is that the engine is shifting and that when it shifts, it is either connecting or disconnecting something.

If the negative side of the battery is well grounded to both the block and the body, then start looking for wires that may move or be pinched when the engine moves.

- Eric

Miles71

It sounds like most of your charging system is working Ok.
The voltage at idle of 14.69 -14.80 sounds a little high.
What is your voltage at 2,000 RPM on the highway?
Your Engine-off battery voltages look normal.

The Olds charging system is designed to turn on the Generator-Light on when the voltage is low. I am not sure if the changing system may also turn on if the voltage is too high? Sorry I don’t have my manuals at work. My Cessna 172 airplane will turn on the Generator light for two reasons, too low and too high voltage.
Since your car off battery voltage is 13.14, we can assume the Gen Light is not caused by a Low Voltage Problem.
Your suggestion that the external voltage regulator is having problem is a good theory. If you are still using a Mechanical Relay external regulator, try replacing it with a solid state 63 amp versions. They are available at most auto stores for about 30 bucks.
Also check and clean the contacts for the external Regulator. Some models have a radio noise capacitor attached directly to the external regulator (check and clean).
My best guess is your old mechanical relays can’t keep up with the alternator and get stuck on, causing a high voltage condition 17+. If you can safely attach your digital volt meter and have your passenger monitor the voltage during WOT you will have more data to use.

MDchanic

I agree that it's good to check the voltage when this occurs, but,

1. This ain't a Cessna, and,

2. None of the above explains the Brake light going on at the same time.

- Eric

rjohnson442

Check all grounds as suggested First. And make sure the voltage regulator has a good ground also. Things are moving pretty fast at WOT this may be why the problem is intermittent. One wire may be shorting out while its moving around. I'd love to find out what the cause of this is. For about a month my jetta decided to pop the trunk release any time you turned the starter over. Never did find the cause just stopped one day

oldcutlass

I'm wondering if it possibly has a broken motor mount and flexing to a bad connection? I'd also wiggle the harness in a few places and see i you can duplicate your problem. Also check the bulkhead connectors.

Do you have an aftermarket voltmeter hooked under the dash?

atkinsom

I will check all the grounds tonight and clean them up. I'll also disconnect all the wires from the voltage reg and clean them as well. The motor mounts are good since I just replaced them last year and I rarely WOT. I don't have an aftermarket voltage meter...just an aftermarket oil pressure and temp gauge.

oldcutlass

What about temporarily wiring in your multimeter and taking it for a ride?

atkinsom

I'll try your suggestion after cleaning the grounds as I'm not very sharp with electrical...learning as I go along. Can you pass on some suggestions on how to wire up the multimeter...I can have my wife look at the results while I do a WOT. Thanks

MDchanic

Just connect the red wire to the battery (+) terminal and the black wire to the battery (-) terminal (or a good ground).

I suspect that the reading will be normal - about 14.5V, maybe 15.
If the alternator suddenly stopped charging, it would drop to 12.5-13V.

- Eric

oldcutlass

The point at which these two lights are common is they are both looking for a ground to light. The fuel gauge, oil pressure gauge, and temp gauge all have a common connection with the brake lamp and the gen lamp (there should be about 5 pink wires connected together behind the dash). When this problem happens do you also get eroneous readings with the other gauges? There are 2 wires that feed those indivator lights. One is tan that goes to the brake pressure switch, the other is brown and goes to terminal 4 @ the voltage regulator.

Fun71

This does not seem right to me. Did you look on the backside of the passengers side head? Many Olds engines have a braided strap from the back of the head to the firewall, near the trans dip stick.

atkinsom

I'll take a look at those gauges after a WOT to see if they give erroneous information as well. Brake pressure switch I assume is the brake line distribution block on the frame rail? I remember a wire coming from there into the dash. Thanks

atkinsom

I'll take another proper gander tonight. Thanks

stellar

Very strange. I think oldcutlass is on the right track. To me it sounds like a loose or bad connection in the circuit for guages. Possibly a cracked fuse (not blown ) or loose or corroded fuse holder. I think it will be a temporary open circuit on the hot feed side of the guage circuit between the ign feed and the guage board. This could be the circuit board the fuse or ign switch or any wiring inbetween. Not going to be easy to find. Intermitant problems are always a pain to find.

atkinsom

Spent yesterday cleaning and reconnecting all the grounds in the engine compartment. Cleaned all the wires and connectors on the voltage reg too. Didn't get a chance to do a WOT yet but now I notice that the gen light does not come on when I turn the key into the ON position. The only light that comes on is the brake light. After starting the car and as I turn the car off the gen light comes on temporarily and then turns off.

I'm trying to find the fuse that controls the gen light and start there. Looked in my owners manual pg 55 and CSM fuse block diag. and there's no specific fuse for gen light system that I can see...can someone tell me which fuse on the block that is for gen light and then I'll follow the wiring as per the above suggestions. Thanks

stellar

Try guages fuse. No lite with key on is an open circuit. Not a temporary open as I said before. Disconnect regulator plug and ground wire #4. With key on in run position and engine not running the lite should be on. If it is on change reg. If it is not on check fuses and ign switch.

atkinsom

The gas gauge does drop a couple of points but I figure that's as a result of the car moving hard and the fuel being pushed away from the sending unit. It stabilizes once the car levels off. All the other gauges are normal you mentioned above. I've cleaned up all the grounding wires I could find in the engine bay(including the one on the block) as well as all wires leading to and from the alternator. Going to track down this gen light issue and then do the WOT test. Will keep everyone up to date as I proceed. Thanks

oldcutlass

Make sure you plugged in your voltage regulator correctly, remember terminal 4 is for the gen lamp.

atkinsom

Thanks Olds. I made sure the 4 wires, which are all on a single plug, were put back in place so that the little plastic bump on the top of the single plug would engage into the voltage reg clip correctly. I also checked that the brown wire was on terminal 4 as per your post and confirmed via the CSM picture. Will plug away tomorrow after work.

atkinsom

Well I was back at it today and the issue has been narrowed down to a bad voltage regulator. I did the test that Mark recommended with the grounding of the #4 wire and sure enough the brake and gen lights came on indicating a bad voltage reg! Then I went out and did a few WOT's and no lights came on this time...again another victory for cleaning all the ground connections in the engine bay. Thank You to everyone for helping me out. Enjoy learning as I go along.
Quick question...I was wondering how hard it would be rewire the connections if I decided instead to get an alternator with a built-in voltage reg thus getting rid of the external voltage reg?

MDchanic

Pretty easy. There are a number of threads on the subject, both here and on every other old-GM board in the universe.
If you google the subject, you'll find every possible variation of descriptions of how to do it.

- Eric

stellar

I think when the #4 wire is grounded, you should only see the gen lite come on and not the brake lite also. You may have another issue, possibly a short between the two. If you go to an internal regulated alt the lite wire circuit will still need to be used unless you choose a 1 wire setup. Maybe Eric can help out with this. I am suspecting a short at the printed circuit.

atkinsom

Thanks Eric and Mark. I'll just let the brake light be for now and start focusing on getting the 455 ready for the transplant with my brother. I have alot of cleanup and degreasing to do before painting the motor. Once the 350 is out of the engine bay I'll use the howto's on classic olds to try and convert to a non-external voltage reg setup...I'm going to get a replacement solid state 63 amp external voltage reg in the meantime just to see what happens. Thanks again everyone.

oldcutlass

Glad you found it, good luck with your transplant.