A friend brougt over his '36 Plymouth for me to rewire, but first there is a charging problem. I wanted to get this figured out before I install the new harness. Here's what's goin on. Car charges at 13.2 v. (on my digital meter) when at idle at about 800 rpm. When I drop the car in gear and rpm's drop the volts also drop to about 12.1. When the headlights are turned on volts drop further to the point that the engine stalls. As long as the rpm's are kept at about 1,200 (or higher) it charges. I have already eliminated the battery (mounted in the trunk), and checked for loose connections, belt tension etc. The cable size is 1 ga. from battery to starter. He said that he had already took the alt. to the shop and had it tested. My theory is that the alt. is not spinnin fast enough due to the ****py aluminum pulleys he's got on it. Maybe he's got the wrong pulley size? Am I just graspin at straws here? Any help would be appreciated.
I had a similar problem on my old malibu. I had to run the 10g wire from the poss pole on the alt all the way to the poss on the batt in the trunk in order for the alt to get the proper signal and charge as it should.. May not be your problem, but it solved mine.
Make sure the engine is grounded and also the alternator is grounded to the engine. If the alternator tested okay and had full output it must be in the alt wiring or mounting/grounding in the car. You did not say if the alt. is enternal or external regulated. I'm ***uming since you took the alt to be checked it is internally regulated. 13.2 volts output sounds kind of low it should be around 14 volts especially when the temp is cool. Unless you have a large amp load at idle for some reason that would explain the lower voltage and the stalling. You might want to check for excessive current draw with an ampmeter if you have one. One other thing did it ever work right in the car and this is a recent problem? The more we know the better the answer will be. Good luck.
Alternator is internal reg. From what I gather from the owner it has never worked right since he's had it. Beyond that I don't know. I'll have to check tha grounding. I think I'm gonna take the alt. off myself and have it tested just to make sure.
Before you pull it off check that terminal 2 goes to the batt terminal on the alt. and that terminal 1 goes to ignition usually with a blocking diode or idiot lamp will also work if you don't have a diode if you don't the car won't shut off.
I had this problem on the 70 Torino I use to have and it turned out the altenator that I had put on had the wrong size pully on it and after we changed it to a smaller pully it worked just great. Gumpa
Yeah. I already thought of that. The alt. is suposedly a 1 wire unit according to the owner. It does have the two terminals on it, but they had a rubber plug over them. I've already pulled it and I'm gonna take it to the shop tomorrow to verify that it is a 1 wire unit and to have it load tested. It looks like a pretty small pulley on it already. Does anybody know what size pulleys are avalable? Thanks for the replies so far guys.
I'm confused - why would a low output alt - stall your motor????it ought to just discharge the battery while the alternator spins slow. Sounds like you have multiple problems to me. Distributor gremlins (loose frayed internal wire) possibly. Just thinking out loud
I thought so too. So I put in a known good hot battery. It ran on the battery for a while then started doin the same thing after the battery ran out. I also had the battery load tested at the parts store.
Car needs to charge at 14.4 volts if it don't then there is a problem with either the dyno/Alt or the reg and or both.Don't forget with lights the voltage will drop but not anything below about 12.4/5 volts...........Marq
As mentioned you might need to run another heavy wire right to the battery from the alt if it doesn't have one already. When you go to the parts place to have it tested they'll probably have a box full of pulleys, ask him to put the smallest one on there he's got with the same width belt.
I say you're right about the pully's, your discription indicates the alternator is trying to charge the battery, to the point of stalling a low rpm pulling motor. The load of a honking alternator is representative of a small lawn mower engine. You will discover a little more speed on the alternator (smaller pully on alternator, larger pully on drive shaft) should put up the missing amps. The test: read cold key off battery for voltage with meter, start and read voltage under charge look for higher value voltage not to exceed 14 volts or so, turn on all electrical loads everything with car idling, voltage should not be below the cold start value. IF the motor stalls tune the motor, the alternator charge load exceeds the motors brake horse power at idle.
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