1937 Non-discharging amp meter

D

Don Helt

Junior Member
I am trying to get a rebuilt generator and electronic voltage regulator (both from C & G) to work in my 1936 pickup. The flathead, 6 volt-3 brush generator, and wiring harness are from a 1937 sedan. When I follow the directions (from Fun Projects) to adjust the 3rd brush with the motor at mid-speed and turn on the lights, I get no discharge. When I turn on the lights without the motor running, I also get no discharge. Until recently, I also got no discharge when I turn the ignition on, but swapping the two leads on the back of the ignition switch fixed that. The swap came as a result of rechecking the wires against the wiring diagram and it’s seemingly all good. I have a stock amp meter (shunt-type) in the dash, an after-market gauge type and a multi-meter. I get no discharge with the lights on from any of the 3 amp meters. The rest of the electrical system works just fine. I’m guessing some wire(s) are still not connected correctly…maybe from the mish-mass of wires coming out of and/or next to the steering box. ​
And if that’s not enough, how can I test the generator by itself and what kind of reading should I expect? Some assistance will be greatly appreciated.​
 
Well seeing that no one has given you an answear I will try. The ammeter on a car usually has all electrical items connected through it from the battery, excepting for real heavy current draw items such as starter motor and solenoid, and horns. It would seem that some main wiring feeds in your car are taking a short cut and not supplying their circuits through the ammeter. If your 36 is as henry built it the main power pick up wire (yellow) is connected to the battery side of the foot starter switch from where it then goes to one side of the ammeter. From the other side of the ammeter a yellow wire goes to the fuse block from where other circuits are connected. You can see that everything has to go through the ammeter and therefore it will read all discharge and charge (generator) current in AMPS. I would guess your car has been messed with, changed or modified. Read and follow these wires on your wiring diagram and find them on the car and connect them where they should go. Its not that hard to do. As for the generator with electronic reg on top it also must have the main charging wire (yellow/black tracer) connected back to the fuse block as per diagram. Check this wire at the v/reg and see if it has power on it using a test light. If the battery is fully charged the generator / electronic reg. will only charge very low, nearly zero. Tell me about your pick up as to whats altered from original specs. That electronic reg has to match battery as per neg. or pos. ground. If this is wrong the reg will be damaged beyond repair. Once electrics have been messed with by experts you could be in trouble. regards, Kevin.
 
Kevin,

Thanks for the quick reply. I'm the expert (not) who assembled my truck from dozens and dozens of parts over several years. The 37 engine came with the (old) wiring harness as so I've used it with some replacements as necessary...and so I've wired the truck. I know the yellow wire to the front of the voltage reg comes from the fuse and is hot. I'll double check the wire the the floor starter button...I remember running a new wire to that. I can also check amperage if any on that with my multi-meter. Do you have any thoughts on how to check the generator itself? I may be slow to reply but I appreciate your advice. Thanks, Don
 
Don, Using your multimeter set to DC VOLTS. Connect probes between ground and battery terminal on regulator.(front terminal). Engine idling reading about 6.3 volts which is battery volts. Rev up engine to say 1500 rpm and voltage should rise up to around 7.5 volts approx. which shows gen is charging OK. With engine stopped You could use your multimeter to check current output in AMPS, provided your meter is capable of reading at least ten amps which many are not. Set meter on DC AMPS (at least 10 ) and remove battery cable off front of voltage reg. and connect meter probes in line (series) between this battery wire and regulator terminal. Ensure connections are secure and start engine and rev up to read amps charging which will vary anywhere between 2 or 3 amps up to the maximum you have set the third brush at. (Should not be more than approx. 15 amps). Your ammeter on dash should also read approx. same as multimeter less the 3 amps the ignition coil draws. The amps charging rate will depend on the state of charge of the battery. If the battery is down the gen may charge higher for some time. A note here that digital multimeters are not ideal for checking generator systems as they tend to jump around on readings some. Use an analogue multimeter or better still a proper automotive test set with needle pointer gauges. See how you go Don. Regards, Kevin.
 
I would say the wire from the battery that go's through the shunt is not the only wire from battery that carries the load from the lights. Also sounds like you had some wires connected to the switch wrong. A good battery cut off switch would be a good idea also. G.M.
 
Thank you again. I checked and I get 'nothing' from my mutimeter when I check both volts and amps with the motor running - at both end of the reg. Interesting and as expected, I get 6+volts from the wire in the front of the reg with the motor off. I gather one or both of the gen and reg are toast, but I think I need to fix my wiring issue first and I'm looking into a new harness. A friend also suggested I c/o the rotary switch at the bottom of the steering column to be sure everything is making contact and is in the right order. Undoubtedly this will all take some time. Kevin,I appreciate your efforts and if you want to send your email to donhelt@gmail.com, I'll let you know how it goes.
 
koates said:
Don, Using your multimeter set to DC VOLTS. Connect probes between ground and battery terminal on regulator.(front terminal). Engine idling reading about 6.3 volts which is battery volts. Rev up engine to say 1500 rpm and voltage should rise up to around 7.5 volts approx. which shows gen is charging OK. With engine stopped You could use your multimeter to check current output in AMPS, provided your meter is capable of reading at least ten amps which many are not. Set meter on DC AMPS (at least 10 ) and remove battery cable off front of voltage reg. and connect meter probes in line (series) between this battery wire and regulator terminal. Ensure connections are secure and start engine and rev up to read amps charging which will vary anywhere between 2 or 3 amps up to the maximum you have set the third brush at. (Should not be more than approx. 15 amps). Your ammeter on dash should also read approx. same as multimeter less the 3 amps the ignition coil draws. The amps charging rate will depend on the state of charge of the battery. If the battery is down the gen may charge higher for some time. A note here that digital multimeters are not ideal for checking generator systems as they tend to jump around on readings some. Use an analogue multimeter or better still a proper automotive test set with needle pointer gauges. See how you go Don. Regards, Kevin.
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Finally found (got lucky) 2 wires from the right side of the fuse that go to the light switch were reversed. Amp meter works fine now - discharges with lights on and/or ignition on. Now on to original issue of generator/regulator, but this should not be such a mystery. Thanks much for your inputs!!.
 
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