Electric problem

[Mun24ster]

There is power in everything under the hood in my switch to 12 volts in my 40 Buick. The problem is no power getting to the push button start from the key when I turn it on. There is no wire going from the key to the push button start. I am wondering where to run a wire from back of key switch to starter button. Not worried about gauges right now, besides they all don't work anyway. Just want to get the car running. Thanks.

[Jim Nelson]

Grab your service manual and go to the electrical diagram.   In all of mine (I have 5) the start circuit starts from the circuit from the 'off/on' switch and goes up to the gas gage and on  to the coil and on to the dist.    In that start circuit,  a wire needs to go to the start button from the primary power circuit and on to the starter solenoid to energize the starter.    That is basically what you need.   It sounds like the srarter button needs power from the main power circuit and then on to the solenoid.   You will find that you must have one side of the starter solenoid going to ground so when you push the button,  power is sent to the starter solenoid.   I assume you have bypassed the vacuum start switch.     I can put together a sketch of the circuit required.   I converted my '38' to 12 volts and I'm redoing the dash wiring on my '35'  (old and not reliable / dangerous  ) and changing to 12 volts also.     I travel with my Buicks so I don't want to have electrical problems while on the road and try to find some 6 volt item . . .  JMHO    If this is a bit confusing,  consider the source as I experience old timer disease. Sometimes I need to review my data but its the 'been there, done that before'  issue.   Ya man .....

[neil morse]

It's very difficult to answer your question without more information.  As Jim mentions, the car was originally wired with a vacuum starter switch on the carburetor that was activated by the accelerator.  Did you bypass this switch, or was the car like that when you got it?  On my car, there are just two wires running from the starter button out to the poles for the vacuum switch.  When you hit the button, it makes the connection that would have been made by the accelerator switch, and the car starts. When I re-wired my car, I left it this way since (1) it’s simple, and (2) it leaves all the other wiring in place so someone can later go back to the vacuum switch if they want to.  If your car was wired the same way, there wouldn't be a wire "from the key to the push button start."  So you may be looking in the wrong place. 

Edited June 22, 2020 by neil morse (see edit history)

[Jim Nelson]

Yes,  the easy way is to use the two wires from the start button in parallel to the vacuum switch.      My '38' had that method done to it when I bought it.       When I had it re-wired with new wiring,  I removed the vacuum switch and wired it as tho that was the normal method to start.

[Jim Nelson]

You did use a "Runtz" voltage reducer for the gas gage.      Don't go cheep because if it fails,  a replacement is not cheep and having to pull the parts can be fun.

[critterpainter]

What Jim is referring to is the the fact that Buick used the + terminal on the fuel gauge as a junction point for the switched power wires.    When converting to 12V those wires MUST be removed from that terminal and  a separate junction terminal needs to be installed and then a separate wire with a voltage drop needs to go to the fuel gauge.   

[Marty Roth]

When we replaced the complete wiring harness for our 1937 Roadmaster,

we added a jumper between a hidden "Starter" button and the vacuum control at the intake. It is the vacuum at that point which keeps the starter from engaging when you "floor-it" while the engine is already running! Minus vacuum at that location, the starter would kick in.

[Jim Nelson]

If you do not utilize the vacuum switch and bypass the switch completely, the starter will no operate unless you push the hidden start button.    This is a change you need to do.   Totally unhook the vacuum switch from your engine.    I had my vacuum switch running in parallel when I got my '38'.   It tried to start when I was accelerating and I was confused why it did it.    I corrected the wiring and the problem went away..     The guy who did the mod did not fully understand what he did.    

[neil morse]

Yes, I should have added that the accelerator switch needs to be disabled if you're going to do the bypass/starter button wiring the way I mentioned.  As Jim says, you don't want to have the two switches trying to work at the same time.

Edited June 22, 2020 by neil morse (see edit history)

[Brooklyn Beer]

I just disconnected the wires on the vacuum switch and ran new (cloth covered) wire to a hidden push switch on the bottom of the column and back to the starter. Key still works as normal.