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MJP MJP is offline
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Join Date: Jun 2007
Posts: 20
Alternator Questions

The Marchal alternator on my 74 isn't working. I get 12+ volts at the battery with the car running from idle up to around 2500 rpm. The voltage climbs to the expected 14+ when I get to around 3000 rpm. The dash light is on while the voltage is close to battery voltage, and goes out as it climbs. I swapped it with a Bosch alternator that I intend to install in a 68 that I'm restoring. That one works fine. Light on at start, blip the throttle and it's out, voltage is up and all's well.

I had the Marchal checked at a local shop that's well respected in this area. They replaced bearings and brushes, nothing else was wrong. I put it back in the car an no change. Back to the shop, they put it on the fixture and it pumps out 50 amps at a reasonable rpm. Back in the car and no change.

I didn't want to hijack "car-wont-charge-melted-alternator-ground-why". I've been following the discussion. I don't understand the purpose of the D+ other than its connection to the dash light. What should I get at that terminal on the alternator while it's spinning? Is there a problem with that post that the shop wouldn't spot under a normal test cycle? Any help would be appreciated.
Old 06-29-2014, 05:16 PM
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