Ignition switch failures.
 

I am wondering if anyone else has had more than one ignition switch fail? I lost one in August of 2018 and one just yesterday. The truck has been driven just over 25k miles between the failures. Both switches failed at the solenoid connection tab. The SOL tab and the ACC tab become shorted together.
The truck has had a new under dash harness installed prior to the first failure. The charging system has been converted from the stock system to a CS130 system and the starter has been converted to a late model GM gear drive starter after the first switch failed. It has been more than a year since both of those modifications were completed.
Photos of both failed units. 1st and 2nd pictures are of the first failure. Third photo is from yesterday's failure.
Thanks in advance for any input.

Re: Ignition switch failures.
 

Just replaced mine a month ago, it appeared to be the original. My problem was it wouldn't automatically pop back from the crank position to the run position it would hit a dead spot and after the motor fired it would die, if I turned it back manually to the run or on position quick enough it would run no issues.

I replaced it with a Standard Motor Products P/N US84T
I also purchased just in case the pigtail plug-in ACDelco P/N PT1964 but mine had no issues so I stashed that in spare parts.

Re: Ignition switch failures.
 

you said you replaced the harness check the connector with it on the switch to see if those two are loose at all . i have had new female pins that were just enough loose to arc and heat the connection . being they got that hot it might be good to replace atleast those two female pins anyway

Re: Ignition switch failures.
 

Had to replace my original after 49 years. Put in a standard brand and it has failed to start 2 times lately. I was wondering if an AC would be better - heard they were mage in Mexico.

Re: Ignition switch failures.
 

The one that just failed was a Standard brand switch. I replaced it with an Echlind brand switch. I disassembled the switch and here is what I found.

Re: Ignition switch failures.
 

Go to post 761 in the link for my post on troubleshooting the failure.

http://67-72chevytrucks.com/vboard/s...698377&page=31

Re: Ignition switch failures.
 

wow i had not seen the other post before or those pics . i wonder if you might benefit from a remote solenoid to take some load off the switch . it seems with all you have checked and changed i wouldnt think wiring i would think the quality of the switches has gone down . i hope you keep a fire extinguisher handy

Re: Ignition switch failures.
 

Following up with this. BigBird05 was kind enough to send me a factory switch to disassemble and compare.
There is a difference in the design of the contacts and how they are operated. But there were some differences I noticed between the two that may lead to the contact failures
New aftermarket switch contacts are cone shaped compared to the factory's dome shape. Which seems to me the factory contacts definitely have more surface area conducting current. In addtion the higher amperage factory contacts are copper. (The 2nd photo doesn't show the difference contact materials very well.)
The other difference that was noticeable is the springs behind the contacts on the factory switch are at least 30 percent stronger.
In the 1st photo the arrow indicates the contact for the solenoid. The contact has a wider wear pattern with little indication of arcing. From the metal shavings it appears this switch failed mechanically not electrically.
In the 2nd photo notice the amount of arcing. It's easy to believe that would be enough to cause the wiring to overheat. The smaller contact area has some got to be a contributing factor. I also believe that stronger springs would help the contacts to clean themselves of arc damage when they pass over each other.
All comments are welcomed.

Thanks to BigBird05 for the switch!

Re: Ignition switch failures.
 

im thinking the factory one started out more pointed . the stronger spring and copper and 50 years made it into a dome shape but that spring probably kept them connected better so it didnt arc so much

Re: Ignition switch failures.
 

Mine would occasionally keep running when I turned the truck off :confused:

Then one bright sunny day when the birds were singing and the breeze was gently blowing, I started the truck and the starter kept going after the engine started then smoke started coming out from under the dash. :m3:

I flew out of the door and opened the hood ... luckily one of the battery terminals was loose enough to pull off with my teeth! :hc:

It only melted the main ignition wire slightly but the switch was pretty much toast .... even if it wasn't toast, it was going to be replaced. Summit Racing had some perfect plug and play switches, so I bought that one and then installed a fuseable link for the next time it decides to tries to self destruct!

Re: Ignition switch failures.
 

I would guess the issue is w/ lower quality aftermarket replacement parts in this case the switch.
The OP could run a relay for the solenoid, but I've run the solenoid off a 16G wire w/o an issue. The inevitable Ford solenoid suggestion is as always nonsense (IMHO).

Re: Ignition switch failures.
 

We've both had the same kind of excitement. :lol:
Where in the circuit did you install the fusible link? What guage fusible link did you use?

Re: Ignition switch failures.
 

I too am assuming the switches are the culprit and was hoping to confirm that with my post. Although it may not become evident unless the truck is a daily/weekly driver.
I have considered wiring a relay in to drop the load on the switch down below a couple amps. If I go that direction I'll be using a 40 amp Bosch style relay no need for a big ole starter solenoid relay here. :lol:

Re: Ignition switch failures.
 

After looking at your photos of the inside of the switch I am starting to see the merits of using a relay in the starter circuit. Do you have a part # for the Bosh 40 amp relay that you talked about? Also which contacts are the ignition on ones. Are they burnt just as bad? With todays increased load on ignition on voltage should we start thinking about more relays instead of just starter and head lamps.

Re: Ignition switch failures.
 

I think a relay would suffer from the same problem and self-weld the contacts together or contacts get burnt so bad they don't make contact any more. So, instead of relay, suppress the arcing by putting a flyback diode from the solenoid purple wire connector and ground.

Re: Ignition switch failures.
 

If you want the best, pick up an NOS Delco Remy switch from EBAY or other sources, preferably in a pull string can.

Part numbers to search for '67-'72:

1116683
1116688
1116695
1116704
1116709
1116711
1116712

Re: Ignition switch failures.
 

I couldn't find the 40amp I had, but here is the 50 amp version Bosch # 0 332 209 137


http://www.texasindustrialelectric.c...0332209137.asp

Re: Ignition switch failures.
 

Thanks I will do some research into flyback diodes.

Re: Ignition switch failures.
 

Thanks for the part numbers. I would rather have an OE switch than have to rework the system.

Re: Ignition switch failures.
 

I have had that happen many times over the past 15 years until I figured out the main culprit.

The heater fan. Turns on when keyed to ACC ON position. Are we correct so far?

Re: Ignition switch failures.
 

Had this happen also!

Re: Ignition switch failures.
 

I don't believe I specifically checked the inrush current of the fan during the previous testing. I will look into that.

Re: Ignition switch failures.
 

Test it on the high setting, you will find that those things draw as many as 40 amps or more depending on what is feeding them.

Higher output alternator is not helping also.

Since completely redoing the underdash wiring harness I do not run the fan on high. Have tried with a 10,15 amp fuse and I keep blowing them so..............

All the fan motors are coming from 2 sources now, and they are rated for both AC and non AC applications. Problem is the non AC truck wiring is only good for a 10 amp motor. Do not know about the aftermarket wiring so it sounds like you have to update that to accept the higher amp motors.

Re: Ignition switch failures.
 

I kept having ignition switch failure so I keep a spare in the glove box at all times. Son, Drew, re-wired The Rocket with a Painless Performance kit so I don't think wiring is the problem. Drew is meticulous with his work and understands electrical systems.

These switches aren't expensive and a spare makes for an easy roadside repair.

Re: Ignition switch failures.
 

The alternator is not an issue here as the engine is not running or hasn't been running long enough to start charging by the time the key is released from the start position. Actually wen the engine is running the newer alternator should provide better voltage control when amp demand is high thus reducing amperage draw across the board. It's that Ohms law thing, when voltage drops, amperage increases.

Heater fan amp draw doesn't vary much from low speed to high speed as the fan speed resistors add to the amperage drawn when they are energized.

Running the AC fan motor with up sized conductors will only lead to heater switch failure. (A lesson I learned the hard way many years ago on my GTO) That's why GM spent so much money designing and installing a A/C fan control relay in A/C equipped vehicles. Instead of up sizing the conductors to run the A/C motor is is much better to install an A/C fan control harness. Something that I am actually considering doing to my Burban. A Suburban has the same heater as a pickup but 4 times the interior volume to heat. I get plenty of heat but not much circulation. Which leads to whining from the back seats. An A/C blower fan may help me with that, but I digress.

I believe I may end to look into getting a different amp meter to troubleshoot this further. Flyback diodes may be a good addition to the circuit but I would like to have more accurate information on the circuit amperage before investing the time in adding them.

Yet another rabbit hole opens .:lol: