I did do a search before posing this question, but couldn't seem to find what I was looking for so.....

When I put my '67 Delta away in the fall, I suspected the alternator to be bad. Car would stall with too many accy's on, then, would not crank without a jump. The gen light on the dash would also stay lit. So, tonight I pulled out the multi-meter and put a good battery in the car. Without the car running, it read 12.7. With the car running, 12.6. With everything on such as lights etc., very minimal change. Difference from last fall to now is, idiot light is very dim and only gets very bright when car is put in reverse! Are there fusible links between alt and batt? Opinions and solutions needed please before I hit the rockauto website....Thanks in advance to all!

 

You should be getting 12.6 / 12.7 without the car running, but somewhere around 14 with it running. Have you done a load test? With all lights and accessories on it should still be charging at least 13.7 or higher. If not, chances are really good you have either a slipping belt or bad alternator. Probably the bad alternator though.

 

I am no expert, but you can always pull the alternator and take to your local auto parts place to bench test for you. I'd it checks out OK, you may want to look at the voltage regulator

 

This does sound like a charging system problem.

What shape is the plug in the alternator is it square or rectangular? If it is square it is an external regulator system with the regulator bolted on the firewall and may be the problem. These can be by-passed for testing purposes or just try a regulator first. Frequent practice is to change the regulator if changing the alternator anyway.

If the plug is rectangular it is an internal regulator in the alternator. Still replaceable by itself but the alternator must be disassembled.

As far as the light getting brighter in reverse that could be due to lower RPM's or an indication of a bad ground. Does it get brighter when in drive?

 

It is externally regulated. only gets brighter in reverse, so I will check a ground. I have a spare VR so I will switch that out, then check again....

 

If the above give no clues and connections look okay, take the alt to a parts store and have it tested. If it fails, bring it home, open it up and look for obvious fails, like worn brushes or such.
An ohmmeter can check the diode trio. These parts are available and can fix your alt for under 10 bucks.
If those are good and you do not want to dive any deeper, then just buy a new one. Keep the old one as many new ones do not come with a pulley.

 

Thanks for all the input so far!

 

 

Very Funny Allan! I switched out the VR, and still the same readings and results with the multi meter. I will have to spend my money on an alternator....

 

Too bad, remember to take the old one with you for core deposit. It would be interesting to see what happens if you ask for them to test the old alt. Are you planning to stay with 55 amp or go to 61?

Sorry Erik, couldn't resist the Johnny 5 tease...

 

I was gonna do RockAuto. If they ask for core, I will send the core. As far as amp, I will see what is available to me.

 

With Rockauto, sending in the core is usually a wash when considering the shipping costs.
If it is bad, see if the brushes are worn - could be a $5 fix. After 100k-200k miles, they wear down.

 

The perk here is you can play with the old one and if you fix it you'll have a spare.

 

Rob, good point, and exactly what I was thinking. Oldcutlass, I will use your suggestion! Thanks.

 

Lite getting brighter in reverse only, makes me think you should check wires for charging system.