alt light comes on at idle. - Page 2 - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #16 of 26 (permalink) Old Jan 28th, 19, 5:32 PM
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Re: alt light comes on at idle.

The issue may be fixed, but is the pulley ratio the same between the current engine and the previous one? It may be that the alternator is simply spinning slower than it used to.
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post #17 of 26 (permalink) Old Jan 28th, 19, 9:29 PM Thread Starter
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Re: alt light comes on at idle.

not sure about the ratio, if anything the big.block front pulley might be a bit larger?
Another thing, even with a new battery, starter, ford solenoid when the car was hot it struggled to crank over like it had too much timing (14*) the battery cables both have clamp on ends, I just went and replaced both and the motor cranks over perfect even when hot.
so we put a 20* can in the hei, lighter.springs. car starts great, runs great. going to swap out the carb.to a 750 vs off the 66 to see if it runs quicker. jim

Jim

70 chevelle, SS clone 454 4 speed
71 camaro. (owned since 1978!) 6-71 blown small block 400
66 chevelle 350 4 speed 3.55 12 bolt
66 el camino 350 th350 parts hauler
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post #18 of 26 (permalink) Old Feb 2nd, 19, 12:42 AM Thread Starter
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Re: alt light comes on at idle.

and the light kicked on tonight. Changed.carb on the car, it's not running.great but took it for a test drive.
turn on lights, at a low sputtering idle the gen light turned on and would not turn off when reved up.
turn off lights and shut off car. start car and light goes off. Should I try another regulator or just swap a newer alternator? jim

Jim

70 chevelle, SS clone 454 4 speed
71 camaro. (owned since 1978!) 6-71 blown small block 400
66 chevelle 350 4 speed 3.55 12 bolt
66 el camino 350 th350 parts hauler
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post #19 of 26 (permalink) Old Feb 2nd, 19, 3:18 AM
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Re: alt light comes on at idle.

If the alt has done a lot of miles, replace the brushes.
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post #20 of 26 (permalink) Old Feb 2nd, 19, 8:15 AM
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Re: alt light comes on at idle.

My alternator light came on but the problem is at the ignition switch and the position it is in. When running, the switch has to be just right or the light comes on. Nudging it a little and it goes off. Never a dead battery and all lights work nice and bright. That's my problem and it's an easy fix.

66 SS-396/425 - M22 -3:73 -12 bolt
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post #21 of 26 (permalink) Old Feb 2nd, 19, 8:26 AM Thread Starter
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Re: alt light comes on at idle.

this is 2 new alternators.

Jim

70 chevelle, SS clone 454 4 speed
71 camaro. (owned since 1978!) 6-71 blown small block 400
66 chevelle 350 4 speed 3.55 12 bolt
66 el camino 350 th350 parts hauler
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post #22 of 26 (permalink) Old Feb 2nd, 19, 8:37 AM
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Quote:
Originally Posted by JWagner View Post
One of the best things you can get for the older alternators is a solid state regulator. They are very affordable.
this is an absolute true statement. It has no moving parts inside to stick. Great advice👍
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post #23 of 26 (permalink) Old Feb 2nd, 19, 10:23 AM
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Re: alt light comes on at idle.

The voltage regulator needs to be grounded to work properly. Almost all GM's of this era had the regulator mounted via rubber to isolate them from vibrations. A dedicated ground strap was used along with a condenser to suppress radio noise. Pulley ratio should be in the 3 to 1 ratio according to Powermaster .If your regulator is not grounded, temporarily hook a ground wire from the base to the core support or firewall to see if this corrects your issue. Make sure that either is properly grounded with ground straps.You should have a ground from the battery to the core support or fender, and a strap from the back of the engine to the firewall.

Last edited by modern malibu; Feb 2nd, 19 at 10:40 AM.
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post #24 of 26 (permalink) Old Feb 2nd, 19, 11:01 AM
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Re: alt light comes on at idle.

Edit to prior post. I should have said a radio noise capacitor , not condenser.
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post #25 of 26 (permalink) Old Feb 2nd, 19, 11:19 AM
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Re: alt light comes on at idle.

Quote:
Originally Posted by JWagner View Post
One of the best things you can get for the older alternators is a solid state regulator. They are very affordable.
I completely agree with going solid state regulator. They look identical to factory (some units you have to swap covers) and I also had buzzing with my regulator that was also brand new. Using a DVM I was showing my voltage spiking to 16.5 volts during the buzzing which is way to high and will damage stuff at that level. Your idiot light will not register high voltage (only low) so check your voltages ASAP in any case. I removed my new old style and replaced it with a solid state regulator. Voltage sits at 14.4v running at any RPM and no buzz! Also make sure you connected the braided ground between the engine and firewall and remove any paint at the connection points and check for zero resistance with your meter.
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post #26 of 26 (permalink) Old Feb 2nd, 19, 8:43 PM Thread Starter
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Re: alt light comes on at idle.

gen light came back on. pulled out the multi meter and it was reading 16.2 , 3 , 4 and climbing. tried a big ground wire to the firewall and motor. no change. regulator is bolted directly to the core support, I even sanded to paint off.
Gave up, went and bought a internally regulated 63 amp alt. jumped the blue and brown wire, jumped post 2? to the battery terminal, hooked the wire wire to post 1? started it, no gen light, 14.4 volts with lights on or off at the battery. I'm done! jim

Jim

70 chevelle, SS clone 454 4 speed
71 camaro. (owned since 1978!) 6-71 blown small block 400
66 chevelle 350 4 speed 3.55 12 bolt
66 el camino 350 th350 parts hauler
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