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**lkt1954** · 12-03-2023, 11:43 AM

I'm having the same issue with my 70 C10. It is a 350 with sniper EFI, dual electric fans and HEI distributor. Wiring is all new (American Autowire) and done by a professional shop.
First time we started it to program the EFI started fine and shut off fine. The second time we started it, guess what it still ran with the key off- unplugging the fuel pump shut it off. During this test run the electric fans would not come on (Derale).
Here is what I have checked and fixed so far:
1. The red wire going into the fan relay was not crimped very good and had worked its way loose. Corrected this and it still was blowing the 30 amp inline fuse. Replaced 25 amp relay and it no longer blew the inline fuse. However the fan control module adjustment does nothing- even at the lowest setting fans do not come on. I'm thinking the control module is shot.
2.The white wire going to the HEI has power when the ignition switch is on and does not when it is turned off.
3. The control module is wired as per directions: red wires to the battery. Module harness: negative wires to the 30 amp fuse/yellow wire to ignition/black wire to battery negative post and green wire to override.
4. I have tried two different and the same results will not shut off when the key is turned off.
5. The only other thing I discovered is that the 30 amp inline fuse on the control module for the fans was blow again. It wasn't when I started it. So it either had to happen when I was trying to adjust the fans or turning the switch off.
6. Installed a 40 amp relay today and the 30 amp fuse is still blowing either when I try to adjust the fans coming on or when trying to shut off the engine (which still runs). In checking the wiring harness on the module- in the 30 amp fuse, the terminal with the negative wires coming from the fan light up a test light whether the ignition is on or not. This confuses me.

Could a bad control module be causing this? The module came with a 25 amp relay, yet the instructions call for a 40/60 amp (so I'm a little confused here- why send a 25 amp-when the instructions call for a 40/60).

Any thought here before I load it up and haul it 50 miles back to the person who did all the wiring?? Sorry this is a long read.
Thanks
Larry

12-03-2023, 11:43 AM	#35
lkt1954 Active Member Join Date: Dec 2007 Location: Dumas, Texas Posts: 188	Re: Ignition switch failures. I'm having the same issue with my 70 C10. It is a 350 with sniper EFI, dual electric fans and HEI distributor. Wiring is all new (American Autowire) and done by a professional shop. First time we started it to program the EFI started fine and shut off fine. The second time we started it, guess what it still ran with the key off- unplugging the fuel pump shut it off. During this test run the electric fans would not come on (Derale). Here is what I have checked and fixed so far: 1. The red wire going into the fan relay was not crimped very good and had worked its way loose. Corrected this and it still was blowing the 30 amp inline fuse. Replaced 25 amp relay and it no longer blew the inline fuse. However the fan control module adjustment does nothing- even at the lowest setting fans do not come on. I'm thinking the control module is shot. 2.The white wire going to the HEI has power when the ignition switch is on and does not when it is turned off. 3. The control module is wired as per directions: red wires to the battery. Module harness: negative wires to the 30 amp fuse/yellow wire to ignition/black wire to battery negative post and green wire to override. 4. I have tried two different and the same results will not shut off when the key is turned off. 5. The only other thing I discovered is that the 30 amp inline fuse on the control module for the fans was blow again. It wasn't when I started it. So it either had to happen when I was trying to adjust the fans or turning the switch off. 6. Installed a 40 amp relay today and the 30 amp fuse is still blowing either when I try to adjust the fans coming on or when trying to shut off the engine (which still runs). In checking the wiring harness on the module- in the 30 amp fuse, the terminal with the negative wires coming from the fan light up a test light whether the ignition is on or not. This confuses me. Could a bad control module be causing this? The module came with a 25 amp relay, yet the instructions call for a 40/60 amp (so I'm a little confused here- why send a 25 amp-when the instructions call for a 40/60). Any thought here before I load it up and haul it 50 miles back to the person who did all the wiring?? Sorry this is a long read. Thanks Larry Last edited by lkt1954; 12-03-2023 at 06:55 PM.