Roadmaster71

1941 Buick: Starter Relay (solenoid) contacts normally closed or open?

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I am installing a new engine and dash wiring harness in my 1941 Buick.

While inspecting my work I noticed that the two contacts on the starter

solenoid relay (one connects to vacuum switch on carburetor and other goes

to voltage regulator G terminal) are closed, even with nothing attached

to them (and no battery in place). 

Are these 'normally closed' contacts? 

(note: the engine started just fine before I started this project so I suspect

the relay is OK. I just need to know I didn't mess anything up.)

 

 

DSCN9975.JPG

Edited by Roadmaster71
Added better photo (see edit history)

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I just looked closely at the shop manual. It seems to me that the two terminals on the side of the relay are connected to either end of the same winding which when energized switches in power to the larger starter motor coil. So, the contacts should be continuous with each other at all times. That’s my guess.

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I believe it's normally closed and the two leads you mention are the double-redundancy that prevents the starter from engaging when the engine is running (say, when you floor it to accelerate onto the highway). If the vacuum switch fails, it still checks for voltage at the generator, so theoretically you should never have a situation where the starter can be energized while the engine is running. I would guess this was the simplest way for them to have both of those redundancies built in, otherwise they would have to figure out a way to make a normally open solenoid close itself only when both of those situations are false, which would probably take yet another circuit.

 

I'm just spitballing here because I've never had mine apart and my pedal-starter switch is disabled, but given how the system is supposed to work, it would make the most sense for it to be normally closed and held open by two separate circuits to prevent accidental activation at speed.

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Wrong.  The contacts are normally open. Take the lid off and look. Push the armature on the relay and the engine will crank.

  • Like 1

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Don is correct, I believe.

 

  The circuit Matt is referring to is the one from the generator. This is a grounding circuit for the starter relay . Grounds the relay so it can operate when power is applied at starting. Opens, ungrounding relay ,thereby preventing the relay operating, when generator begins to charge.

 

  Ben

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After that vac switch hanging up too many times to count away it went. I found it really cool till the mad dash around the car to yank the terminal off the battery as the starter would not shut off.

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Interesting discussion. Whoever worked on my car before I owned it disconnected the vacuum switch. They installed a starting push button and a disconnect switch which I always had to turn on before starting. 

There is supposed to be a redundant system that prevents the car from cranking after it starts even if the vacuum switch hangs up. I don’t recall the details but I suspect it as Ben described.

 

I have a new carb installed with a functioning vacuum switch so I want to try out the original system. A couple of my friends who have the same system run a starting button to the vacuum switch just in case it gets stuck open. I may do that also.

 

Thanks for the comments.

Edited by Roadmaster71 (see edit history)

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