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12-29-2022, 03:56 PM | #1 |
Registered User
Join Date: Aug 2022
Location: Austin, TX
Posts: 17
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72 C20 voltage regulator question
Hi all,
Hoping to get some help with a charging issue I'm having with my '72 C20. It uses an external voltage regulator (EVR). For some background, I recently completed an engine swap (old 402 out, new 540 in) during which I put brand new wiring harnesses in under hood. Alternator is also new. When I start the engine, the alternator does not kick in. When I disconnect the ground wire from the EVR to the radiator support, the alternator kicks in and starts feeding the battery. That's the opposite of what I'd expect given that the EVR needs a good ground. I found this out by accident while checking for voltage at various wires (tan at the EVR plug, white at the alternator plug) as I've seen suggested elsewhere on the forum. I've also tried a new EVR. I've consulted the wiring diagram but am not sufficiently knowledgeable on how charging systems work, so would appreciate if anyone here could help me troubleshoot. Thanks in advance! Grant |
12-29-2022, 05:19 PM | #2 |
Registered User
Join Date: Aug 2022
Location: Austin, TX
Posts: 17
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Re: 72 C20 voltage regulator question
OK I figured out my issue - on the base of the EVR there is a terminal that sticks out the side - it used to have a capacitator attached to it, and the capacitator was attached to the firewall. I thought it was like that when I bought the truck - I guess I got the re-installation wrong. I assumed this was the ground. It's not. Grounding this out was causing my issue.
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12-30-2022, 12:37 AM | #3 |
20' Daredevil (Ret)
Join Date: May 2003
Location: Jefferson State
Posts: 13,722
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Re: 72 C20 voltage regulator question
Glad you got it figured out! I had zero ideas.....
__________________
- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
12-31-2022, 07:22 PM | #4 |
Post Whore
Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,357
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Re: 72 C20 voltage regulator question
Welcome to my world of self Inflicted misery. Good job on figuring out the problem!
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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alternator, charging, regulator |
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