1948 charging issue

J

jeffsang

Junior Member
Hello All


Working on my 48 coupe, flathead 8 everything original. Checking battery voltage while car is warming up and as it reaches operating temp reving 1500-1800rpm,

I'm getting 7.4-almost as high as 8 volts, which I realize is a bit too high. As the car gets good and hot and engine is heat soaked, stopping and starting a few times, I'm only now reading battery voltage, about 6.25V. Seems like something is cutting out as the engine really gets hot and quits charging. What should I be looking at? Could use some input and direction. Thanks


Jeff in Ohio
 
Sounds like your battery is about done. Take it to a parts store
and have them do a load test, free. You may want to try an Optima.
Best prices on the internet. G.M.
 
Jeff, Get your car hot and up to the point where it is not charging again, leave it running and disconnect the field wire, (middle one ) from the voltage regulator and move/connect it over to the Armature or Gen terminal. Rev engine up and read voltage at generator terminal of regulator which should go to 8 volts plus. This is providing the generator is Ok. We have bypassed the regulator field control here and the generator will charge flat out if it is working OK. If there is still a low voltage reading of 6.25 volts then the generator is faulty. If the voltage is 8 volts plus then the voltage regulator is faulty and requires attention. Also very important that all battery power connections and earths a good throughout the car. Check battery terminals, starter solenoid terminals, ammeter terminals, etc. Should be tight, clean and not getting hot to the touch during operation. Regards, Kevin.
 
Koates
I switched the wires on the regulator after the car quit charging again and still only got a little over 6 V. So Im going to take the generator and 2 voltage regulators back to the repair shop for another look. I forgot to mention I did put on a new voltage regulator a year ago with the same results. I am also using a good optima battery. Could something be cutting out in the genny that would stop the charging process? The car charges fine until it warms up, up to 8V then quits and goes to approx 6.2V.
 
Jeff, Plenty of things to go wrong inside a generator. The armature could be one suspect item. As the armature winding heats up it might develop a short in the winding if the winding has been overheated at some time in the past or the winding is loose and being effected by heat and centrifugal forces. I hope your generator shop or auto electrician has the skills to be able to check this out correctly. Some shops with younger tradesmen don't have good skills in working with old equipment. They need an armature growler to do tests on the winding. Regards, Kevin.
 
Had generator shop go through my generator and adjust both voltage regulators to approx 7.4 volts. Still not getting consistent charging output. It goes to 7V barely and sometimes just a little over 6. My lights do not get any brighter when revving engine above idle. Battery and engine is grounded good to body, but I would like to add a good ground wire from body to frame. What kind of wire should I use to accomplish this?
 
Anything will work, if it's large enough gauge. I found some braided strap about 1/2" wide (it looks like a miniature battery ground strap) that I think looks like it belongs there. I'm trying to remember where I got it. It wasn't hard to find IIRC.
 
Hello
I took my generator with both voltage regulators back to the electrical shop for testing. They said gennie was good and set both regulators at 7.4 volts. When installed in car, they charge at first, then after a bit, all I get is battery voltage, like the generator quits working. Do the voltage regulators need adjusted on the car with everything running? My charging gauge in dash seems to be working fine also, it goes from the middle to toward charge when revved up then quits after a while. When I pull the light switch, there is no charging. I added a ground strap from engine to frame and a strap from body to frame. also have one from engine to body. I'm checking voltage at battery. Using an Optima red top. I have absolutely no problem starting the car, it starts quickly and runs great, just can't get gennie to keep charging..
I,ve also replaced wires from gennie to voltage regulator to rule those out.
 
Just grabbing at things here, but you do have the dedicated ground wire from the generator to the voltage regulator? And you are sure that ground has a good path to the chassis ground?
 
Yes, I have the seperate ground wire between the two, will double check to be sure its good.. I ground firewall where voltage reg. attaches. Also ran new ground from firewall to frame, clean shiny connections. Also wire wheeled where gennie mounts to engine. What is crazy is that both voltage regulators start acting up once engine is good and warm. They both work early on.
 
Jeff, Connect your voltmeter across the battery and read voltage with engine not running. Should be 6.3 volts on a charged good battery. Start engine and rev to approx. 2000 plus RPM and hold there for 3 or 4 minutes. Voltage across battery should be approx. 7.2 to 7.5 volts at the end of that time. It might be useful to take the car to the auto electrical shop so they can test the charging system in place. Report back. Regards, Kevin.
 
Could it be that the battery is charged up so the generator doesn't have to put any charge into it? My ammeter reads a big charge when I set off but falls back to just a slight charge once everything has stabilised.

Mart.
 
jeffsang said:
Hello
I took my generator with both voltage regulators back to the electrical shop for testing. They said gennie was good and set both regulators at 7.4 volts. When installed in car, they charge at first, then after a bit, all I get is battery voltage, like the generator quits working. Do the voltage regulators need adjusted on the car with everything running? My charging gauge in dash seems to be working fine also, it goes from the middle to toward charge when revved up then quits after a while. When I pull the light switch, there is no charging. I added a ground strap from engine to frame and a strap from body to frame. also have one from engine to body. I'm checking voltage at battery. Using an Optima red top. I have absolutely no problem starting the car, it starts quickly and runs great, just can't get gennie to keep charging..
I,ve also replaced wires from gennie to voltage regulator to rule those out.
Click to expand...

If the generator weren't charging, the ammeter would show a discharge when you turn the lights on. If the battery is fully charged when you pull the light switch, you might see a negative blip on the needle, and then return to zero or a very slight positive charge. Remember the ammeter reads only current going to or from the battery (except for starter and horn). When the battery is fully charged the generator will provide current to the ignition and lights without showing on the ammeter.
 
Hello All
An update to my charging issue. I'm trying to do everything I can myself before taking car to electric shop who worked on my gennie and voltage regs, 40 minutes away. Anyways, I installed a new generator belt since I,ve thought mine looked kind of worn.. Gates #TR24538 for anyone looking for correct belt for 46-48 passenger car. Upon starting car, checking voltage at the battery as usual, I'm now getting my 7.5 volts when sped up and when engine is good and warm, even after repeated checking, stoping and starting the car. I'm good with that. Problem is when I pull the light switch and turn on lights, the charging stops, I barely get 6.3 volts when sped up. Why would the charging system stop working when I turn on the lights? What should I look at next?
 
Also make sure you don't have any shorts in the lighting circuit, do you have a headlight relay?, make sure lighting circuit also has good grounds.
 
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