VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 34 Generator Cut-out

That helps a lot.

It looks like a wire goes from the POST on the Generator to the Resistor on the Light Switch. How can I tell if the Resistor is burnt out?

Have a look at that youtube video around the 1min mark. He shows how to use the meter on the "ohms" range. It will likely have an omega/upside down horseshoe symbol on your meter.

After you set your meter on the ohms scale. touch the red and black leads together and hold them. The meter pointer should swing all the way to the right. This shows ZERO ohms. Pull the leads away from each other and the needle swings back to the left. This shows INFINITE resistance as you are basically measuring open air.

Make sure car is off. Now to test a resistor, put the meter on ohms again. Put a lead from your meter on each side of the resistor and hold them firmly to get a good connection.


The meter will do one of three things:

1) Needle does not move: reposition the lead ends to ensure a good connection and try again. If meter still does not move after several tries for a good connection, the resistor is likely OPEN. Like a blown fuse.

2) Needle swings all the way to the right: Resistor is VERY LOW RESISTANCE. Might be defective but might be correct as resistors can have a large range by design.

3) Needle swings somewhere to a mid point on the meter scale: This is what I would expect your resistor to look like if it is good.


This is a crude go/no go method to check the resistor. Resistors are marked with numbers or coloured bands so you can accurately check them but we are just doing a pass or fail test here. The typical failure is to open up like a fuse in #1 measurement above.

I gave my father my (expensive at the time) old analog meter years ago and he eventually gave it back to me and he bought a $20 digital multimeter instead. Even a cheap digital meter will make this a little bit easier for you as there is less interpretation. Try the method above but eventually would be worth buying a digital one (but keep both) if you are ever going to work on your car again...

Thanks, I'll try it when it warms up. If this Resistor is bad would it keep the Generator from showing a charge?

From your question posted on January 28th:
Answer posted on January 28th:
Follow the excellent instructions posted by canadiantim above on how to test the resister with your multi-meter and you should have no problem determining if the resister on the back of the light switch is defective. Let us know what you find.

I've been told that the POST on my 34 Generator is a Ground. I don't think this is correct. I would think the Generator would be Grounded thru the Mounting Brackets. According to my wiring diagram the wire from there goes to the Resistor on the Light Switch. Which is correct? And if the Resistor is burnt out can it be restored to original? Again I guess if the Resistor is burnt out that would be the reason I have no reading on the Amp Gauge?

If you have a single post on the generator or single wire then it is the output (6 volts positive). If there is a post and a wire or two posts then one (wire) is the output and the other is to the field coils. Changing the power to the field coils changes the power output. The resister on the light switch serves to alter the generator output. Since I don't have experience with them I can't give an educated response to failure of the resister.

The other post on the generator is the field post. The wire that is connected to the field post goes to the resister on the headlight switch. Check your wiring diagram.

The generator is grounded through its mounting on the engine.

Great, that is what I thought. Now can the Resistor be repaired if it does not work?

Get a look at the resistor and get it tested and go from there. It's possible the resistor or the switch assembly can be replaced or repaired but I'm not familiar your wiring. Maybe you'll simply find a frayed wire or loose connection...

Jon, Take a look at this old post. If the link doesn't work just search "1934 Master Light Switch Resistor" Mike

https://vccachat.org/ubbthreads.php/ubb/showflat/Number/385122/Searchpage/1/Main/59692/Words/%2B34+%2BMaster+%2Bresistor/Search/true/1934-master-light-switch-resistor.html#Post385122

Problem solved. The resistor on the back of the Light Switch was burnt out thanks to suggestion by Gene. Also one Generator had the "Third Brush" bracket bent so it wasn't touching. Gauge works now. Thanks to others besides Gene who helped. It helped being able to use the Volt Meter. I now have an extra Generator which I'll probably never use.