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Quick question about ignition switch Amp rating.

I have attatched a photo of the back of my ignition switch. its from a 1956 3100 With s 235 engine with foot start. I have looked in the maintenance manual, build manual and searched the web to the best of my ability.

Does anyone know the Amp rating for this ignition?

I know there are work arounds like relays and an actual fuse panel.

At this point its more of a I want to know rather than a I need to know.

for some reason its in my head that 35 amps is the correct answer. just no idea if its correct and no idea where it came from.

According to the wiring diagram, the battery feed wire to the ignition switch is 12 gauge. According to This Chart a 6 ft long (probably longer than the actual length) can handle up to 30A. At 4 ft long, a 12 gauge can handle up to 50A, so the ignition switch is likely rated for somewhere between 30A and 50A. I have never seen a published rating for the ignition switch.

Thanks Klhansen

Its intrresting to me that there is information on prety much every stock switch, motor or bulb. Nothing on the ignition switch. my switch has a position for an additional 5 accessories. One position was used for turn signals and one for the heater motor. I plan to add electric wipers, Radio and AC. That would fill out the other three positions.

Relays would prevent potential overload so its realy just an issue of Knowledge for knowledg sake.

I Think I will try to find a parts dealer who sells that particular type of ignition switch and see if they have any info.

Just realy curious.

That is a switch originally for a V8. The foot starter switch only has 3 poles. Here is a replacement OEM style switch from Classic Parts.

Maybe 7 or 8 years ago a late friend (electrical engineer/designer) gave me data on ignition switches from the 1950s, the 1960s and 1970s. What I learned was that some were only rated for a max of 10 or 15 amps. Some others later were rated for a max of 20 amps but none were ever made to handle more than that except for a few special purpose switches for industrial/wrecker/heavy equipment use and those as I recall were rated for up to 30 amps. The other thing I learned from a gentleman who ran one of the NAPA stores here was that almost none of the switches they handled were marked for amperage ratings and you had to either get those ratings from the box or the data accompanying the switch or the company's data. He told me 30 amp was the highest rated three position keyed switch he could source.

This question came up when after converting to HEI and installing an electric puller fan my ignition switch failed. The HEI on start-up required around 28 amps and the puller fan needs around 25 amps. Essentially after just short use the contacts fused together and would not release. I ended up using a 30 amp rated switch made in Taiwan by a company named URIAH and a couple of 60 amp Bosch style relays to reduce greatly the amp needs of the switch. I did in a box in my attic find a switch made in the USA and sold by Standard Products. I had bought it around 1978 however I have no idea what the amperage rating is and there is no product number on the switch so I decided it wasn't worth the gamble. This same switch was made originally by AC Delco and copied by Standard and later by other manufacturers all over the world. The URIAH switch is an exact copy of that switch but rated at an honest 30 amps.

Hope this is helpful.

Here's Jon's URIAH UA424100 4 position switch with 30A capacity

https://www.murdochs.com/products/a...-dc-universal-ignition-switch-with-keys/

There are some on ebay for $12- $20

Phak1. Thanks for the information. This switch has two positions. On/run or off. So since it came on the truck, I figuerd it was either original or most likely one a PO added. Wouldn't the V8 ignition switch have a 3rd "start" position?

John G. Based on what you have said, I'm going to have to get used to not knowing.

Otto. Thank you for the link.

This is realy just curiosity on my part.

The acc position will be used to power relays, so the amp draw should be within the switches rating.

The simple fix is to install a continuous duty magnetic switch powered by the ACC position on the ignition switch. Those are available up to 100 amps capacity or so, and they resemble a Ford type starter solenoid. The difference is that they're designed to stay engaged for hours at a time. Use about 3-5 amps from the ACC terminal to power the relay, and feed a separate bus bar or fuse panel for high current accessories. That's the fix I used to protect headlight switches on big rigs with dozens of clearance lights.
Jerry

Hotrod Lincoln. Thank you for the recomendation.

For instance:

www.ebay.com/itm/176138878186?

Jerry

A little more versatile relay than the one Jerry linked to would be a 4 terminal relay with an isolated coil. Rather than using the case for grounding, it could be mounted to a piece of wood or other non-conductive material with the 4th terminal wired to a grounding point.

Hot rod lincoln and Klhansen,

Thank you for the information.

When I intialy started working on my wiring harness, I could not find informatiin on the amp rating for the Ignition switch so I bought a 120 amp relay to power my Acc fuse panel.

The lack of information about the switches amp rating kept eating at me though. Not in a serious way, just a Hmm why is there no information in the manual.

I could not find the answer in the assembly manual or several shop manuals. (car/Truck) Interestingly the instruction sheets for the add on junction block from that period show how to connect to the key for accessory power but says nothing about amps, or poitential overload.

I decided to ask here because of the welth of knowledge and experience.