Hey all,

Any ideas? The car runs great all day long, but as soon as night falls and I turn on the headlights it drops right out of idle when I come to a stop.

My initial thought is the usual suspect - the alternator. But I was talking to a guy and he said may have some ties to the Vacuum.

I am pretty new to this whole home-mechanic thing (and loving it by the way!) Is there an easy way to test the output of my alternator? Or is it a different issue?

Any input would be greatly appreciated.

It sounds like the alternator, or the internal regulator. Also check the belt for looseness. If there's an idle step-up solenoid on the carburetor, it may not be working or out of adjustment.

The belt is definitely fine that was my first guess.

If the electrical checks out fine I'd take a closer look at the vacuum issue. A simple way to check for a leak is to pop the hood and have a helper behind the wheel start the car, let it run at a fast idle for a couple of minutes, pop the lights up using the override switch below the steering column, and then shut down the engine. If there is a major vacuum leak you'll be able to hear it for a short bit after the engine noise is gone. If you do hear a hissing sound and can't locate it quick enough you may have to repeat the starting and stopping of the engine a few times as you reposition yourself around the quadrants of the engine compartment.

Or as mentioned in other threads get a vacuum pump and check out all the vacuum lines without having to run the engine.

Good luck!

Actually I had the same problem with my 75. Everything was fine, until I turned on my lights, right !!! Well, after thinking about this, I decided to do some tracings. The lights seemed to be the problem. My troubleshooting experience is simple, and it goes like this. Switch, circuit breaker or fuse and finally component. Since it didn't seem to blow a fuse, it was probally a shorted connection. When my engine would die, I would also lose power, sometimes briefly. I was able to get the engine to die, then going from the switch, I followed the wiring and didn't have to go far. I was able to get the power back by pulling on the main light wiring coming from the fuse panel, forward. Raising the hood, and right under the master cylinder, I found the problem. Brake fluid had worn away the wiring. It looks like this wasn't the first time it had happened, as it had been repaired before. I replaced the wire from the fuse box and rerouted the wiring so that brake fluid would not drip on the wiring. Look here first. Be carefule, as if the wiring is totally bare and you wiggle or pull on it, you may short it out. In my case the wiring was so corroded, it would not carry any current. The wire is easy to track, as it it the biggest wiring coming from the fuse box panel. Let me know if this is the same problem. Hope this helps.

Thanks guys,

I will check it out and let you know what it was.

This site is awesome. Gives me a real appreciation for how difficult it probably was prior to the internet to restore a car.

As they say strength in numbers!!

Generally speaking,
a vacuum leak has to be pretty bad to kill an engine at least that's how it's been with my cars with an otherwise good healthy engine, also in most cases when you spring a good vacuum leak the rpm's will jump up,

Seems it's a short like Bill is talking about.
Best of luck and Keep us posted, you are so right about strenth in numbers.
Cheers,
T.

Hey Bill,

Had a look for a bad wire, was it pretty obvious when you saw it? I couldn't see anything but I didn't look well enough yet.

If it turns out to be the alternator, does anyone know off hand which size a 72 requires? I have no air-conditioning. When I look on Ecklers there are 3 different amp sizes?

Thanks!

I cdan't answer your question on amp size but I bet it has to do with the size of your engine. Give ecklers a call and tell your year and engine size

Unless you are going for purist stock go with the biggest they offer,
my 86 runs a 106 I believe it is somethimg just over 100 amps, I scored it after calling around for a best price with life time free replacement at Advanced auto parts.
Cheers, P.