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The ammeter needle bounces wildly at idle, then pegs when engine is revved. This is a replacement ammeter on a '64, bought through Hemmings. The original ammeter did the same thing, until the needle snapped, melted or disintegrated. Any ideas are greatly appreciated. Thanks.
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Re: Bouncing Ammeter Needle
Have you checked the voltage regulator? They take some special equipment (a shunt) to check, but you can easily take it off and take it to an auto electric shop to be checked. If there is not one handy, I think a parts store replacement can be had for less than $20. I don't usually endorse changing parts for troubleshooting purposes, but it sounds like you are risking breaking another ammeter unless you do something quickly. The $20 regulator is probably cheap compared to another ammeter and if you don't end up needing it you can always sell it on eBay for three times what you paid for it. -
Re: Bouncing Ammeter Needle
Ammeter should respond to state of charge produced by the alternator. The voltage regulator is responsible for monitoring the charge state of the battery and calling for alternator charge as required.
If the V-reg is faulty and tells the alt to charge/stop charging/charge/stop charging because its interal relays are intermittent, you ammeter will oscillate in lock-step to the malady.
If the 'sense' wiring to the V-reg is corroded and the V-reg actually 'sees' the battery intermittently, the same symptoms can occur. Battery is there but in need of charge, WAIT! the darn battery disappeared altoghether charge like HECK, hold it-battery's back; turn the charge down....
Most auto electric shops can put the car's charging system on a scope/monitor and NAIL what's going on for a few $$$ in a few minutes. No need to 'shotgun' this/that component by guesstimation....Comment
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