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Alternator idiot light question
Posted by: mattlockwood ()
Date: November 21, 2020 04:42PM

Alternator question:
Engine running. Turned on the lights and the gen light blinked on bright for a moment , then is now very dim light continuously. Also, on startup, the light takes a big rpm rev to extinguish , rather than quickly going out. Also, getting 17 volts out of the alternator, at the electrical connection of the alternator

Bad voltage regulator?

This is a corvair motor in a vw bus, with an alternator conversion. The electrical setup for a “1 wire” alternator is the same for a bus and a corvair. 85 Buick internally regulated AC Delco alternator

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1970 VW Bus- converting to a 110hp w/a PG



Edited 1 time(s). Last edit at 11/21/2020 04:43PM by mattlockwood.

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Re: Alternator idiot light question
Posted by: 63900CV ()
Date: November 21, 2020 04:55PM

17 Volts is way to high.

If you have a "One wire Alt" you do not need a regulator.

Disconnect the wire at the ALT and start the engine and read the voltage being outputted from the ALT

Hope it helps

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Re: Alternator idiot light question
Posted by: mattlockwood ()
Date: November 21, 2020 05:03PM

I’ll give it a try.

It’s a “1 wire”(really2). The VR is internal and also replaceable

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1970 VW Bus- converting to a 110hp w/a PG

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Re: Alternator idiot light question
Posted by: CoCoCo ()
Date: November 21, 2020 05:05PM

Bad regulator or it's not sensing the proper voltage from the battery.
Is the rest of the electrical system in good shape?
When you say it takes a big rpm rev to turn out the lamp, how high are you talking? Usually 1500rpm is more than enough, so if it's taking more than that I would suspect the unit is bad.

But I'm not familiar enough with them to know how to test it's components on the vehicle. Try what 63900 said and see what you find.

Good luck.

Paul

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Re: Alternator idiot light question
Posted by: mattlockwood ()
Date: November 21, 2020 05:13PM

Just “thinking out loud”
It’s prob either the VR or the ground from the alternator not the engine block is loose. I’ll check it out tomorrow and report back.

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1970 VW Bus- converting to a 110hp w/a PG

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Re: Alternator idiot light question
Posted by: 66vairman ()
Date: November 21, 2020 05:38PM

A 1985 Buick alternator is probably a 12SI unit. You want to use a 10SI unit bolted up to the Corvair front 10DN housing and fan/pulley (unless the engine was modified for revers rotation!!).

It sounds like someone tried to make the DELCO a "1" wire. Either it's not wired up correctly, or someone put in an aftermarket "1" wire alternator regulator pack. These conversions require the alternator to run at a higher RPM (rev up the engine) to energize, then alternator stays on at idle.

I'd suggest checking to make sure the alternator is correct and wired up properly with the sense line to the battery (connecting it to the alternator output terminal works, but not recommended) and check the warning lamp connections.

Do be careful as an incorrectly wired sense terminal can drive the alternator to voltages that will damage the car's electrical items. At 17VDC I suspect the sense line input is open (there is an internal circuit to prevent excessive voltage runaway when the sense line input is open or not connected.

Wiring diagrams are in the FAQ's on this site.

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Re: Alternator idiot light question
Posted by: cnicol ()
Date: November 21, 2020 06:07PM

Matt wrote: "1-wire is really two"

Craig replies: You either have a 1-wire alternator (not recommended) or you have a 3-wire alternator. Only having two wires on a 3-wire doesn't work so well.

BAT terminal goes to the battery/vehicle B+

Terminal #1 goes to the charge light to excite (start) the alternator and then operate the idiot light.

Terminal #2 goes to the battery for voltage sensing at the actual positive battery post.

Without #2 connected, most regulators will output 17-volts or so.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Alternator idiot light question
Posted by: chris ()
Date: November 22, 2020 06:46AM

Matt, is this a recent changeover or have you been running it for a while? If it's going bad, Mike Dawson has internally regulated alternators that he converts and are ready to bolt on.

'65 Monza 4 door
4 speed
110hp
Gardner, KS

Heart of America Corvair Owners Association

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Re: Alternator idiot light question
Posted by: mattlockwood ()
Date: November 22, 2020 03:09PM

No continuity between #2 terminal and battery cable terminal, so I suspect the terminal is old and crusty and needs replacing. Will update smiling smiley

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1970 VW Bus- converting to a 110hp w/a PG

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Re: Alternator idiot light question
Posted by: Grandpacorvair ()
Date: November 23, 2020 04:32AM

Pretty sure you can simply connect pin 2 to the heavy wire to the battery at the alternator as a test or a fix if that's where the problem is....

Kerry Borgne
Birmingham, Michigan

1963 Spyder Convertible

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Re: Alternator idiot light question
Posted by: mattlockwood ()
Date: November 23, 2020 03:12PM

Success! It was simply a bad connection between #2 terminal and the battery.

I had discovered that I had no continuity between #2 and the battery and Craig and Kerry’s suggestion to jump a wire between the two (duh- why didn’t I think of that?) made the light extinguish and the alt voltage to drop down to 14.8. Quick replacement of the pos battery terminal clamp fixed it permanently.

Thanks everyone for helping.

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1970 VW Bus- converting to a 110hp w/a PG

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