Very hot ignition switch

I suspect my switch has some sort of short or other issue.

After a nice drive today pulled it into the garage and the car would not turn off. With the key out, the ignition light was still on.

Fiddling with the key found a spot that would turn off the car (and trap key) but looking at it funny would resume it’s ACC position. I cannot start the car as the key really doesn’t do anything now.

The switch was so hot it burned me and blistered on contact.

This is a 1970 S2 2+2. Am I best just replacing the switch? Any part numbers? Will I need new keys? My ignition and doors are not matched so I guess it doesn’t matter.

Thoughts?

Thanks!

Sounds like a bad switch, they can go high resistance and melt down. The switch and lock are two different parts, you may not need the key part. I’d take the switch off the back, then see if the lock mechanism works alright.

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David,

Check the advice given by Dennis on May 15th in this thread:


Or maybe check your switch very carefully for a number stamped into the aluminum housing and then check out eBay seller nosimport. He just happened to have the exact N.O.S. replacement of my switch.

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This gives me a lot to think about. I have a retro air unit and I did not install it myself. Makes me wonder how this is all wired and if simply switching the ignition switch will be enough.

Thanks!

David,
I believe you recently added A/C , were you running the A/C just before experiencing the issue?

In the end, I believe the corrosion between the ignition switch lugs and the rivets that hold them created the resistance that caused most of the heat. I also had dirty contacts on the A/C fan relay as described AND the initial install of the system incorrectly ignored the A/C relay on the left side mud shield. Everything is well now and I have moved the fan load to fuse #4 which unloads the ignition switch altogether. The recommended headlight mod, adding relays to the circuit, is next!

I did have the ac on

Ok. So everything is cooled off and I went for a look.

How can I remove the ignition switch— see pic?

I have the AC off but when I reconnect battery with no key it still thinks car is on. Before the issue, the key did feel weird…

I don’t want to start prying things off but I’d like to know how to properly remove the switch ( how do I get that cover off)?

Just wondering if the installers used a relay for the A/C or tapped in the ignition switch (wires) for power.

Somebody with a series II can surely help you here as your switch installation is somewhat different than mine. This parts diagram does look like it might be your setup though:
https://tinyurl.com/y532wyvf
I noticed that item #12 in the diagram appears to have slipped down and out of position in your picture.
Just be absolutely sure the battery is disconnected before messing around with the switch.

Lastly, take a very close look at the wires shown in this blowup of your picture:


The spade terminal cover on what looks like the brown wire looks very dark/discolored and deteriorated. Mine looked like that but not as dark. Also, check the “kink” in the brown wire and the contact it makes with some metal(?) in the surrounding area. Do I see some “blackening” of the copper wire coming out of the brown insulation wrap? You probably ought to thoroughly service this area and then count your blessings that all you suffered was a blister!

Looks like you have a steering lock, I don’t, so what I say must be taken with a grain of salt. The electrical part of the switch is on the back of the lock section, if yours is like mine there is a grub screw on the side of the cylinder that holds the electrical switch into the mechanical part. I am suspicious the access to the grub screw is going to be blocked by the air conditioning, so you might have to lower the steering column to access it, but I am uncertain. Look around on the sides of the cylinder for a straight edge screw, loosing that should allow the electrical part of the switch to then be pulled out the back. Don’t just yank the spade lugs off, take a picture of the wire placement first, that way you have a chance of having it work when you are done. From your picture you may also be crimping some new lugs onto your wires, clearly there is at least one that is cooked.

Thanks. I think I want to get to the key barrel as a first step to see if I can get it started and properly on/off and then mess with the switch part (with battery disconnected, of course).

Any advice on how to get to the key barrel through that cover?

Thanks and keep the suggestions coming!

David;
The cover of the ‘key barrel’ (13 in the SNG picture) is hel in place by a small slotted screw on the medial side of the cover. Either use a offset screw driver or drop the steering column down to get a good access.09
This photo shows the screw I am talking about and what I think you are asking about.

Regards, Joel.

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Joel,

Very helpful, thanks. Do you have a pic of the rear of that switch or the wiring diagram for it.

I may try the standalone switch/key as a bypass and see if it’s this unit. The standalone is way cheaper than the wheel lock one so may be a good test and backup.

Thanks!

David;
I do have a wiring diagram for the switch but I will have to go through a bunch of papers so it may be a couple of days.

Regards, Joel.

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In case it helps here are photos of my original switch from my '68 that fried several years ago. I replaced it with Lucas 34680 that came with new keys but I swapped the key tumbler over for my original key.


David
68 E-type FHC

Thanks all. I am going to bring it i to a shop for them to check over but I installed a bypass ignition switch to get it there (it’s tape wrapped so should be good for a few miles). :rofl:

There were two switches used with the SII Britax column lock like you have. There was a phenolic based one and a plastic based on. I know the plastic base switch is notorious for getting hot like you describe. I don’t know about the phenolic one. The contacts inside the switch get corroded and oxidized which creates resistance and the result is heat. The only thing you can do is disassemble the switch and file and lightly sand all of the contact points. Also the spades on the back need to be very clean. Check to see if there is ANY resistance between the rivets and the contacts. Any resistance must be corrected.

This is a picture of the back of the plastic base switch. The Lucas part number is 39679A

This is a picture of the back of the phenolic base switch. The Lucas part number is 39679B.

To disassemble the switch you have to VERY carefully bend back the three tabs that hold the back on. VERY slowly remove the back noting where everything is located. There is a ball in there that facilitates the spring-back lock out. Be sure you assemble the switch with ball and spring tabs in the correct positions. Here are some pictures of what the inside looks like:

I used some epoxy to assist the tabs when I re-assembled mine because the springs tend to try to keep it apart. With the un-avoadible damage you will do to the tabs, it really helps keep the switch together.

The wires on the back of your switch appear to be heat damaged. That should be fixed as well.

The best thing is a new switch but these have been NLS for the SII for many years. As an alternative the SIII switch will fit your lock and work fine. It is still available from the usuals. See https://www.sngbarratt.com/us/#!/English/parts/9a8a9460-c7f6-4800-a290-434506447073 The difference is that the SIII switch has no spades and the wires riveted onto the plastic base. The wires go to a connector so you will need to use your imagination to connect the wires from this switch to your harness.

image

Richard Liggitt

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I cleaned mine out and installed it. it lasted a couple of months and the key got hot again .I had a new switch i changed the tumbler and was able to use my original key.
The switch was from;
https://www.bpnorthwest.com/jaguar/e-type/ignition-switch-4-terminal-w-accessory.html

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Thanks all! Very informative posts.

As from my post above, we wired up a bypass ignition switch so I can bring the car in. I’ve been wanting to try a blithering shop and this will be a good first task. I am also having them make sure the AC is not direct but through a relay per above links.

Have a few other issues I need it in for so armed with all this let’s see what they say.

Thanks!