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Troubleshooting your Corvair Alternator

Updated on March 1, 2010


A common scenario is you go to start your car after sitting all night. Your battery is 100% OK. Yet, it is dead when the key is on OR you are driving and suddenly you stop. In either case, it may be the alternator. In the first example, a diode within the alt may be defective and draining the battery overnight or there is something else causing it to be drained. In the second case, the alternator is not recharging the battery as its being driven so the car is using the battery for its power.

If you suspect the alt, take it off and take it to an Autozone for a free test. Alternators either have built in voltage regulators or not. The original corvair alts did not have them built in, which is why there is voltage regulator on the firewall. If this is not working correctly, you might hear a clicking sound. If not working, there is nothing regulating how much voltage the alternator is creating which can be as much as 30-50V. If you touch your alternator after 10 min of running, it may be warm BUT it should not be too hot to touch or fry an egg. If it is, the voltage regulator is not working properly, not hooked up correctly. Running a car in this mode will eventually fry your battery.


Attach a voltmeter to the battery. Run the engine. With engine running, it should read 12-12.5V. Increase the rpms by accelerating in neutral, the as the rpms increase to 2000, the voltage meter reading should increase up to 14V. This is OK. While in this mode, turn on the headlights and radio, the voltage should drop to 13V or so. This is normal. Continue and turn off the lights etc. Voltage should rise to 14V. Now take your foot off the accelerator, voltage should be 12-12.5V.

If your test is like this, the alt is recharging the battery as you increase speed. This is good. Also, it tells you that the alt is being regulated by the voltage regulator. However, you may still have a faulty diode that drains a battery when left connected! Beware! If your test has voltage higher than 14V, the regulator may not be working. If your meter starts off fine, but drifts past 14V, the regulator is not controlling the voltage the alt makes.

The two smaller gauge wires that attach to the alt can be cross connected. One of the wires (usually the light colored one) is for gen light on the dash to light up. The dark one is for voltage. If these are not correctly connected, the gen light will not work when the key is ON in the ignition. If the dark is not

connected right, your alt will NOT recharge the battery at higher rpms, so on the volt meter in the test there would be no increase in voltage to 14V as you increase rpms, it would simply remain 12-12.5V.

The light colored wire attaches to the R connector(bottom), the dark wire, to the F connector (top).

An alternator with a built in regulator is identified by it having air vents on the back, the two connectors are labeled 1 and 2, not R and F, and the bracket that matched the corvair alt (no built in regulator) does not work. The alt is usually larger and heavier. If you have this, the regulator on the firewall must be disconnected and a conversion kit used available from Larry’s corvair for $25. Very easy to install.

Since the alt is very easy to remove, if it is a suspect, remove it and have it tested.


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    • perrya profile image

      perrya 7 years ago

      yeah, but he reopened it in Harbor city, I think, He is on Ebay

    • profile image

      Rodney 7 years ago

      Larry's Corvair in Gardena, CA closed it's doors 4/2009. For your alternator conversion kit please contact Thank you.