HELP - 701 Ignition Switch Gets Hot

[rmaynard 14,907]

HELP!!

I finished wiring the 701 today. The engine runs great and I have about 13 to 14 volts at the battery when running 1/2 to full throttle.

Here is the problem. While running, the ignition switch gets extremely HOT. 

Wired as shown in the 701 wiring diagram, the 12 volts comes from the + terminal of the battery, to the B lug of the ammeter, then to one side of the switch. When the switch is turned on, it goes to the + lug of the coil.

What is making the switch get hot? Could I have a bad coil? Engine runs fine, Could it be a bad switch? I guess I could jump the switch and see if the wires get hot. Or I could find another coil and see if that's it. Any other ideas? Otherwise I'm stumped.

 

[squonk 38,949]

The only thing the switch on a 701 does is power the coil. Amps cause heat. So you're flowing too many amps to ground. If you were to take the switch out and leave it hanging in mid air and turned on, if it still got hot it would be your coil as the culprit. If the switch is mounted in the plastic dash same thing. I would toss another coil on first to see what happens. Is the coil staying cool?

[rmaynard 14,907]

31 minutes ago, squonk said:

The only thing the switch on a 701 does is power the coil. Amps cause heat. So you're flowing too many amps to ground. If you were to take the switch out and leave it hanging in mid air and turned on, if it still got hot it would be your coil as the culprit. If the switch is mounted in the plastic dash same thing. I would toss another coil on first to see what happens. Is the coil staying cool?

Coil is cool. I threw another one in and the switch still got hot. I'm taking the switch out now.

[rmaynard 14,907]

Connected both leads together and no heat. Taking switch apart now.

[squonk 38,949]

Probably worn contacts inside raising the resistance.

[rmaynard 14,907]

14 minutes ago, squonk said:

Probably worn contacts inside raising the resistance.

Opened it up. Didn't look bad. Cleaned and burnished the contact. Put back together and still HOT. Put both wires on one terminal and it stayed cool. Guess my two prong key switch is toast.

[squonk 38,949]

14 minutes ago, rmaynard said:

Opened it up. Didn't look bad. Cleaned and burnished the contact. Put back together and still HOT. Put both wires on one terminal and it stayed cool. Guess my two prong key switch is toast.

I have a DC clamp on ammeter that I keep in my truck bag. I'll have it with me if you still have issues at the show.

[rmaynard 14,907]

It's the switch. I wired in a plain old toggle switch and it's fine. Thanks for your help.

[Handy Don 10,622]

May not be the contacts themselves. It might be the rivets that connect the external terminals to the internal contacts. If you and crunch them a bit tighter you might get a few more years out of thatr switch!

 

[rmaynard 14,907]

Don't have time to worry about it now. Will fix it when I get back from the show. I have a weeks worth of things to do and only two more days to do it.

@squonkMrs. M is checking the pantry to make sure she has all she needs for making the bars.

[rmaynard 14,907]

11 hours ago, Handy Don said:

May not be the contacts themselves. It might be the rivets that connect the external terminals to the internal contacts. If you and crunch them a bit tighter you might get a few more years out of that switch!

Don, I think you are on to something. I woke up early this morning (actually didn't sleep) went out to the shop as soon as the sun came up, got my Fluke meter out and checked my probe to probe reading, 0.00 ohm. I put my meter on the terminals of the switch and got a 0.16 ohm reading. So I took the switch apart again and tapped the rivets. Put the switch back together and now I have a 0.00 ohm reading. After I have my morning coffee, I will reattach it and test. Keeping fingers crossed.

[rmaynard 14,907]

 @Handy Don Now I know why you are called handy. You made the correct call. Everything is good. Switch is running cool. Thank you.

[Handy Don 10,622]

2 hours ago, rmaynard said:

 @Handy Don Now I know why you are called handy. You made the correct call. Everything is good. Switch is running cool. Thank you.

More than welcome, Bob, and delighted it’s worked out. 

I’ll be sure to stop by at the show to admire your work!

 

Now I’m hoping the info I’m giving to the very reluctant and skeptical service manager at the car dealer will work out as well.

Edited June 20, 2023 by Handy Don

[rmaynard 14,907]

1 hour ago, Handy Don said:

Now I’m hoping the info I’m giving to the very reluctant and skeptical service manager at the car dealer will work out as well.

Good luck. Car dealers will only do what is in their company approved manuals. I had a problem with my parking brake on the Tacoma. Dealer refused to do what I suggested, so I had to do it myself. The Tacoma forum had a whole section on parking brake issues. They figured out the problem/solution, but Toyota refuses to concur.

[squonk 38,949]

So the rivets that are connected to the contacts which are essentially part of the contacts were loose and I get no credit?  Just for the heck of it I tested my 857 amp draw with just the key on.   . 2 of an amp. I would love to have known what was flowing through that switch. 

Edited June 20, 2023 by squonk

[Handy Don 10,622]

25 minutes ago, squonk said:

So the rivets that are connected to the contacts which are essentially part of the contacts were loose and I get no credit?  Just for the heck of it I tested my 857 amp draw with just the key on.   . 2 amps. I would love to have known what was flowing through that switch. 

The less than perfect connection (resistance) is converting those ohms to heat.

[kpinnc 10,767]

On 6/20/2023 at 7:38 AM, rmaynard said:

Switch is running cool. Thank you.

 

You two just kept a 62 year old switch in service. Well done! 

 

I've seen Bob's work on round hoods. I will certainly miss seeing them this year!