Author Topic: Ignition switch keeps burning out?  (Read 328 times)

SgtKish

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Ignition switch keeps burning out?
« on: October 27, 2019, 07:05:35 PM »
I am about done on this complete rebuild of my m3a1 halftrack, and she is beautiful. The problem I'm having now is getting her to start. I have all the systems working except for one ignition problem. No voltage getting to the coil. I ripped apart the dash again and realized the master power switch I cleaned up and was working when I installed it burned out. I put in a new one, turned the power on and again heard that ugly sound of cracking and popping. The switch burned out again and both wires coming off that switch were hot and almost melted. These wires are both 10ga. I have checked all wires they all look correct. The gauge never shows any amperage. The coil has the wire coming from the amp post on the dash gauge to the positive marked terminal on the coil. The neg on the coil goes to the distributor points, and of course the thick middle coil wire going to the center of the dis cap. I dont understand what is going on here. If it was just a switch, I dont think the wires would be getting this hot. Please any insight would be so much appreciated. Thank you

Mark

spillmk1

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Re: Ignition switch keeps burning out?
« Reply #1 on: October 27, 2019, 07:31:59 PM »
I'd take the wire off the + on the coil and see if the problem goes away.
Maybe a bad coil?
If you have an ohm meter you should be able to measure a low resistance from the switch to ground and figure
out the issue without frying switches. Doubt that the switch is the problem.
But again.....if you have the above meter you can check the switch and see if it's shorted internally to ground.

Hope this helps!!!
Keith
1955 M38A1
1952 M100
1941 M2A1
MVPA Member

SgtKish

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Re: Ignition switch keeps burning out?
« Reply #2 on: October 27, 2019, 10:08:49 PM »
just noticed that the temperature wire that goes from the back of the dash gauge to the engine block is really hot. I just found it because it burnt the hell out of my hand. Is it possible I have the 5 wires from one post of the amp gauge on the wrong post? The cardboard that lays over those 2 posts say 60 and 65. I have the 2 wire from the harness on one post and the 5 other wires on the other. Does it matter what side you put them on, because the manual doesn't state either or?

spillmk1

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Re: Ignition switch keeps burning out?
« Reply #3 on: October 28, 2019, 06:26:47 AM »
just noticed that the temperature wire that goes from the back of the dash gauge to the engine block is really hot. I just found it because it burnt the hell out of my hand. Is it possible I have the 5 wires from one post of the amp gauge on the wrong post? The cardboard that lays over those 2 posts say 60 and 65. I have the 2 wire from the harness on one post and the 5 other wires on the other. Does it matter what side you put them on, because the manual doesn't state either or?

If you reverse the wires on the amp gauge, it will just read backwards.

Wire to temp gauge hot?
Original gauge used a capillary tube (small hollow tube)...not an electric wire.
The capillary tube is hot?
That would be weird. Would definitely be a path to ground if touching a hot wire.

You have something grounded and/or shorted out.

Keith
1955 M38A1
1952 M100
1941 M2A1
MVPA Member

SgtKish

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Re: Ignition switch keeps burning out?
« Reply #4 on: October 28, 2019, 04:45:31 PM »
I finally narrowed it down to the fuel gauge grounding out. I took the cluster apart and found one of the metal washers holding the coil and ignition switch wire was welded to the cluster back plate on the fuel gauge.  So that post was arching to the back plate. The fuel gauge from what I can tell looks fine. It's not burnt and all the small wires inside are connected still. Why would that particular post arch like that? Is there suppose to be plastic washers holding that gauge to the plate? Is the two hot wires on the wrong post, or does it matter? I have the fuel gauge tank switch on the outside post, and the coil and master power switch on the inside post.

spillmk1

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Re: Ignition switch keeps burning out?
« Reply #5 on: October 28, 2019, 07:38:05 PM »
Here's the back of my gauge before I cleaned it up. There is an insulator around the posts.
Is yours like this?

The gas gauge will read backwards if wires are reversed.

Keith
« Last Edit: October 28, 2019, 07:40:12 PM by spillmk1 »
1955 M38A1
1952 M100
1941 M2A1
MVPA Member

SgtKish

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Re: Ignition switch keeps burning out?
« Reply #6 on: October 28, 2019, 11:50:44 PM »
No it does not have an insulator. I took a stab at it and made a rubber on. When I got everything apart I realized one of the washers were welded to the back of the gauge. I just got everything back together and she is good to go. Now I'm having issues with the timing. It is quite confusing as its written in the book. Thank you for the insite, you were dead on with the insulator missing. Can I ask you about timing set up or should I make a new post about timing? I'm guessing its 180 out because the book says plug 1 is the opposite side of the distributor when the flywheel is on tdc.

Smadge

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Re: Ignition switch keeps burning out?
« Reply #7 on: October 29, 2019, 07:47:34 AM »
Mine was 180 deg off as well so I took the spark plugs out and turned the engine by the fan to line up the marks.  Was a lot easier then hit or miss with the starter butten.
1941 M2 Autocar (restoring)
MVPA# 36810E

spillmk1

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Re: Ignition switch keeps burning out?
« Reply #8 on: October 29, 2019, 10:41:49 AM »
No it does not have an insulator. I took a stab at it and made a rubber on. When I got everything apart I realized one of the washers were welded to the back of the gauge. I just got everything back together and she is good to go. Now I'm having issues with the timing. It is quite confusing as its written in the book. Thank you for the insite, you were dead on with the insulator missing. Can I ask you about timing set up or should I make a new post about timing? I'm guessing its 180 out because the book says plug 1 is the opposite side of the distributor when the flywheel is on tdc.

Make sure #1 piston is at top of compression stroke.
Will appear you are off 180 degrees if at top of exhaust stroke.
Insert distributor so rotor points at position for #1 plug wire.
If you're not a perfectionist....#1 plug wire position can be anywhere on the cap....of course as long as the rest of the firing order is correct. ;)

This help?
Keith
1955 M38A1
1952 M100
1941 M2A1
MVPA Member

SgtKish

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Re: Ignition switch keeps burning out?
« Reply #9 on: October 29, 2019, 01:57:11 PM »
Is it possible that insert that goes on top the oil pump and the distributor locks into, can get flipped to the wrong side. I'm not exactly sure why that would mess anything up considering it just turns the dist. I do think it got stuck to the bottom of the distributor as I was pulling it out and I heard it fall back in the hole. It wasn't sitting down all the way. So I turned it till it fell into place. Just spit balling here, does  it matter. Then of course i listened to the book and after having it tdc on the compression stroke. I fipped the distributor router 180 and locked it back down. Now I get one putter if I'm lucky. So I'm going to try again with the basics like you said and I'll report back soon. Thanks, Mark