Pilot Dan

Here is an update to my prior post on Voltage regulator adjustment on my 59 and a new problem that came up. Bought an aftermarket (NOS made in USA) regulator and installed it to get back on the road. Start the car up, good charging rate 13.8 V, and everything appears normal initially. Drive around for about 20 minutes, and I notice the guage starting to head to just a slight discharge with no load (NO accessories or lights on). When I add a load, (lights, blower fan ect...) there is a definite discharge and I confirmed I am not getting a charge (only battery voltage 12.6 or lower) with my volt meter . I swapped out the Generator with my freshly rebuilt one just for grins (even though the old one tested OK) and same problem next day, charged till it warmed up, then stopped. These new regulators have no adjustment screws as the old original GM ones did, so I have nowhere to go with this problem as far as any warm adjustment. Also have a NEW Lectric Limited Gen harness and the ground appears solid. Any ideas???? Could this be a grounding issue?? Pilot Dan

1955 copper

I've had this problem many years ago and it took a old man to tell me that the engine assy was not grounded to the frame vary good when hot. So he added a jumper cable from the engine to the frame to show me , then the starter worked well when the engine was hot .So I'm just saying to check the engine to frame ground or add a extra ground cable and see if that solves your problem. you may have a poor grounding problem in the Circuit

1snake

Do you have the ground strap on the drivers side of the front engine mount?

Jim

Pilot Dan

Good thoughts. Yes, I do have the Copper braided ground wires on each side of the front motor mounts. I will try the test again with a dedicated ground wire right to the battery and see if there is any change in the charging rate when warm. Thanks for the suggestion.

Pilot Dan

I connected a jumper wire directly from the battery to the regulator ground and this did NOT do a thing. Same scenario, 13.8 V at cold start, and not charging warmed up. Other than trying another NEW regulator, is there anything else to check in the electrical system I missed??

1snake

Try extending your temporary ground wire to include the generator as well. If it still has problems, drive it until it acts up and then without shutting the engine off, carefully disconnect the wires from the generator and hook your volt meter to the armature terminal and a ground. It should show a reading of 2-6 volts. Now ground the field terminal and rev. the motor a little and it should go up to around 15 volts. If you have these results, your generator is not the issue when it's warm.
How's the battery?

Jim

Pilot Dan

Jim, battery is good and Generator is NOT the issue. I tried swapping them and it did not make a difference. One thing I read in the Shop manual was adjustment of the Voltage regulator when the engine is warm. They present a chart that basically shows the regulator Voltage will drop as the ambient temperature increases but not below 13+ volts regardless. Problem is the new regulators don't have adjustment screws
like the old ones did. I may have to try a different regulator at this point and hope for better luck.

1snake

Heat causes resistance. I was trying to help you rule out one of the possible problems. The only way to do that is to test each component while warm and the problem is presenting itself. The voltage reg. is one item I've never messed with. In all the cars that I've owned that had the mechanical VR, I've never pulled the cover off one because I never had a problem with any of them, and never noticed any performance issues whether hot or cold. Good luck finding your problem.

Jim

Pilot Dan

You are correct, heat causes resistance which is why the adjustment procedure is supposed to be done after the engine reaches operating temperature which just happens to coincide with when my voltage drops off. These new regulators have no adjustment screws, so you are basically stuck with wherever the manufacturer places them initially. I had tried to adjust my original with some success per the shop manual but was not completely satisfied with the result.

My conclusion at this point is to have the original one (which can be adjusted) rebuilt as I am willing to bet the new regulator is the problem.