47-55.1 Push Button starter with Fan Kill Switch

[vintovka]

Does such a switch exist? Need to momentarily turn off the Spal fan while starting engine. My dash has the original hydromatic push button starter.

[greg_h]

How about having the pushbutton switch activate a solenoid that has a normally open contact and a normally closed contact. When solenoid is active, starter motor turns and the fan circuit is opened. Let off the button and the circuits reverse function if that makes sense. That work?

[joedoh]

if you used a standard gm wire harness you can hook the fan relay 12v+ (the trigger, smaller wire, running to 85 or 86 on the relay) to the orange or brown on the ignition switch, both will be off during cranking.

I am assuming your fan relay has a heavy gauge 12v+ from the battery, a temp sender/switch that is grounded, and the other side goes to "ignition". replace that ignition with a fused wire from the orange or brown wire in your harness. on with key, off while crank.


edit: looking at your hyromatic pushbutton I realize that your key probably isnt i the crank position so that may not work.

greg h solution would work in that case, you could use a standard automotive relay and interrupt the 12v+ ignition wire with the starter signal. so

pin 85 to starter signal wire from hydromatic button.
pin 86 to ground
pin 87 to ignition
pin 87a to fan relay ignition pin(replaces the wire that was there, you can use that wire on pin 87)
pin 30 empty

[mr48chev]

I'm thinking that the simple way might be to hide a round push button brake light switch under the dash for the hand that doesn't push the start button and not far from the ignition switch. Most of those switches are in the off position when the brake pedal pushes the button in and in the on position when the pedal is pushed away from them.

I'm not sure what amp load they will carry but if you are triggering a relay with the wire from the ignition that shouldn't be an issue. This for show and tell but I liked the metal body. I think it is actually for a 6 series BMW https://www.amazon.com/Standard-Moto.../dp/B000E5DILY Most 60's and 70's GM cars and trucks have the plastic body version.

I had a toggle switch and push button under the dash of my 48 for a couple of years when I lost my keys and had to do an emergency fix to get home one night and the shop I worked in had a supply of push button starter switches and toggle switches . My buddy rode in the truck a number of times over several months before he noticed that I didn't have a key in the igniton.

[vintovka]

Using a brake light switch with CC kill (via a relay) as a starter button has merit. Going to think about that. The use off a momentary kill switch for left hand use also worth thinking about.

[mr48chev]

You could just put a toggle switch in for it but that brings the chance of forgetting to turn it on.

[vintovka]

Originally Posted by mr48chev

You could just put a toggle switch in for it but that brings the chance of forgetting to turn it on.

Chance heck. With my old brain its a certainty. I checked distance from starter button to under just under dash below it out of sight. A little awkward but can push starter button with thumb and reach a momentary kill switch with fingers. May be simplest solution since Starter button is wired directly with solinoid. Thinking kill switch would momentarily interrupt ground to fan relay. What do you think.

[mongocanfly]

I know my 4wheeler has a relay that's drops the fan out while cranking...for me the relay would be the best option..

[vintovka]

Think I solved it thanks to 48chev brake light suggestion. Thanks!!!

Took a spare GM brake light switch and used the front two contacts (they are NC when button is out, rear ones are NO). Spliced it into the relay ground and it works fine. Button is on dash bottom and easily reachable with thumb on starter and fore finger on kill switch. Tough to see if you not looking for it


The Spal fan draws 25 amps and makes it a pita to start when hot and Kicks in at 210f. I do think i will eventually add a second battery (built for it already), a gear reduction starter and high output alternator. This truck is kinda a cross between a tank and a fighter plane. Overbuilt and Dual systems wherever possible and driver is always armed. Will post pics later.