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A few months back my starter button switch became intermittent and trying to spray it with contact cleaner just didn't work. I replaced it but saved the old one for future disassembly. I took it apart yesterday by carefully unbending the 3 crimps and then gently pulling it apart. As can be seen on the photo, the 3 contacts and the metal disk that closes the circuit(s) were pitted and dirty. Also the vinyl/rubber dirt shield was deformed and not sealing well but was keeping the contact cleaner from reaching the contacts. I'll clean up the contacts and disk and keep the switch as a spare but I don't think a full refurbishment is feasible. The new switch was not inexpensive but if it lasts another 40+ years I'll be happy.

Mine came without a starter button, so I just bought one at the local truck supply shop for about $15.

ako wrote:Mine came without a starter button, so I just bought one at the local truck supply shop for about $15.

Be VERY careful with this. I'll bet that the one you installed is a single circuit intermittent button as that is what is very readily available everywhere. Your problem will be you have 3 wires going to the stock starter button and you CANNOT double up 2 of them on the same pole.

a - (+) comes from ignition switch to 1 pole.

b - (+) goes from 1 pole to ballast resistor to give additional voltage on startup.

c - (+) goes from 1 pole to starter solenoid to actuate solenoid.

Which lines are you going to double up?

If a + b on same pole you have just bypassed your ballast resistor 100% of the time and will fry your ignition or coil eventually.

If b + c are on same pole your starter solenoid is engaging anytime the key switch is on as the power back feeds from the ballast resistor.

If c + a are on the same pole your solenoid is running anytime your key is on as it is bypassing the switch itself.

If you have found an intermittent switch that isolates the 3 poles and only brings them together when the button is depressed PLEASE post up the part number as we would all be very interested in it. If you have simply incorrectly installed a 2 pole intermittent switch, you need to do some checking as you will have problems.

Final note: If in a situation where you need to use a 2 pole intermittent switch, leave the (b) wire disconnected and taped off. Your truck will still run and may be a little harder to start up, but you will not be creating problems for the short haul.

Paul - Awesome photo's on the starter button. I'd like to cross post them to another board if it's OK with you.

Cheers,
Scott

ExpeditionImports wrote:Paul - Awesome photo's on the starter button. I'd like to cross post them to another board if it's OK with you.

Cheers,
Scott

Fine with me Scott - post away!

Happy 4th!
Paul

Scott is exactly correct; a single circuit (two terminal) switch just won't work as a direct replacement to the stock three terminal switch.

That said, if you add a diode to the lead to the ballast resistor you can use the two terminal switch: Since the ballast resistor always has power when the engine is running, connecting it to the starter solenoid means that the solenoid always has power

If b + c are on same pole your starter solenoid is engaging anytime the key switch is on as the power back feeds from the ballast resistor.

but you can prevent this by placing a diode in series with the ballast lead wire; you can use one of these diodes: http://comingsoon.radioshack.com/6a-50v ... ZmFr_lVhBc. The diode is placed with the band end towards the ballast resistor, and the unbanded end connected to the solenoid and this end also connects to the starter switch. The diode acts as a one way valve for current: pushing the switch applies power to both the solenoid and the ballast resistor, through the diode. Once the switch is released, the diode prevents power from flowing from the ballast resistor back into the solenoid.

Obviously, the simplest thing is to just replace the starter button with new (or NOS) from our vendors. But if you decide not to, the above is probably the best way to use a simple two terminal switch.

Gents,

I looked at the electric schematic at the start-button and it is a simple switch, 3 leads with no connection until pushed; then all 3 connect
I could be wrong, but I thought that any high-amp DPST push-button-switch would do...
You just short the two sides of the two arms = connection-01 and the two other contacts are contact-2 and contact-3. This way all 3 leads leading to the start-button are independent, i.e. no contacts in between and when you push the button all three connect.
Or am I seeing something wrong, if not: switches are between 10 and 20 $ all over the place

Jules

PS if not clear I'll try to send a picture

Thanks to the replies above, I will need to recheck everything now.

When I got my Pinz the starter and ignition and quite a few of the other electrical components were all missing.

It worked out what most wires seemed to do with a multimeter, wiring diagram and some trial and error. Now I can't remember off hand how the starter button is wired.

Add another job my my snag list....

...You just short the two sides of the two arms = connection-01 and the two other contacts are contact-2 and contact-3. This way all 3 leads leading to the start-button are independent, i.e. no contacts in between and when you push the button all three connect.

"and when you push the button all three connect" Yes, but you have hardwired contact-2 and contact-3 (if I understand your post). These should not remain connected when the button is released.

One contact is 24V power (call this contact-1); this is connected to the solenoid (contact-2) when the button is pressed to cause the starter motor to crank the engine. Under cranking conditions, the battery voltage is lower than normal (and the voltage is much lower than when the engine is running) so contact-1 also supplies power to contact-3 which bypasses the ignition ballast resistor, essentially "overdriving" the ignition to ensure the hottest, best spark during cranking to do the best job at getting the engine started. Once it is started, the button is released which stops the starter and solenoid and ALSO stops bypassing the ballast resistor so that "normal" spark happens.

If the solenoid terminal and ignition terminal are tied together, one of several bad things will happen: 1. the ballast resistor will burn out due to the additional draw from the solenoid; now the ignition is dead. 2. the solenoid will stay pulled in continuously, ruining the starter and/or ring gear. 3. The additional current draw from the solenoid will drop the voltage to the ignition, resulting in weak spark (and probably followed by #1).

The starter switch was designed that way for a reason, and it is a good reason. The simplest fix is to replace the button with the correct button. There are other work-around possibilities, but they are more complicated, more costly, and more effort than just replacing the switch with the correct one.

Oops, just re-read Jules' post -- yes, a DPST switch WILL work when the two poles each independently connect power to both the solenoid and the ignition independently. But finding a DPST or DPDT push button switch that can handle the current are contact arcing will be tough to find, I think.

Jim your suggestion to use a diode isolator is very practical.
Schottky power diode would have a low drop and work fine.

You could also eliminate the ballast resistor and go full EFI

ron

You could also eliminate the ballast resistor and go full EFI

Been there, done that, have the t-shirt. Wouldn't ever go back!

Gents,

Try this link:

https://www.digikey.com/product-search/en?FV=fff40011%2Cfff80061%2C2080003&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=0&pbfree=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25

This shows a page with DigiKey, DPST push button switches in all types and colors, with LED lights, literary hundreds of them, drool hours over what you want your start button to look like: Prices from $2 -$20, 10 Amp, 16 Amp and 20 Amp.

If you filter, the highest DC amp rating available is 10DC, then filter by Off/On, there are only 11 available. They are all 20.20mm dia. and 12V illumination.

What's the amp draw is on the switch?

Hmm, I guess I didn't realize how many DPST push button switches are available. But for the Pinz application (with the inductive kick from the solenoid, and a slightly lesser kick from the ignition system) the arcing is going to be pretty hard on the contacts - that's why the OP showed how pitted the contacts had become.

Whoa...

Sorry gents, but I realized that the switches must also be a momentary connection, but if you google "DPST momentary push button switch high Amp, there are opportunities, then again you could also use the low Amp but pretty start button to switch a heavy duty car relay

I found a 20 Amp Westinghouse switch (SWP) XRS44537: https://www.surplussales.com/switches/swpushb-3.html 1950 surplus switch to start motors...

Good luck

Jules