Fast idle mod. gone wrong

[Gone Huntin']

I did the fast idle mod. on my truck today with everything being done just as in the article. The truck was warm when I did the mod., so when I tested it the coolant sensor in the head was in the "off" mode. I drove the truck to lunch and everything was fine. I came out of work to leave tonight and started the truck. It activated the fast idle and ran for a few seconds and then shut off and wouldn't restart. I had no "wait" light, no power to the ip, gp controller, or coolant sensor. I found that the newly installed diode had burnt through the doubled heat shrink tubing and a fusible link on the pass fender had burnt also. When this happened, the new manual switch was in the off position. I'm wondering if the ground for the lighted switch that backfeeds through the power out terminal when the switch is off is enough to cause a short. There is an ohms reading of .026 between the power wire from the switch and ground. If I unplug the ground to the switch for the light in it then there is no continuity to ground on the power wire with the switch off. Anybody had any issues with this before? I am an A.S.E. mastertech and I'm very comfortable with wiring, but this one stumps me if it's not with the switch ground issue.

 

[Agnem]

Definitely sounds like there is a problem with the switch. .02 ohms is not a light bulb. That sounds more like the loss in your meter leads. Sorry you had the problem. Is it possible that you wired up the switch wrong?
If you switch the power and ground around, you can see where you would get into serious do do.

 

[Dsl_Dog_Treat]

Wondering about the switch as well, I have a lighted switch installed as well and no problems.

 

[Mr_Roboto]

I know I've wired those lighted switches wrong before, you have to look real close at the diagram on the side and mark each terminal so you don't get turned around.

 

[Gone Huntin']

Well, I tried it again today and everything worked great........with the ground for the switch unhooked. As soon as I hooked the ground up it did it again. Keep in mind that there is no problem with the switch on, only when the switch is off. I'm just running it without the ground for now.

 

[Agnem]

Sounds like the switch is designed to ground the switched output when the switch is off. Handy if your tying it onto a CMOS or TTL circuit input, but obviously very bad for general 12 volt wiring.

 

[skippytdi]

Hi.
Newbie here.
Possible to post a link regarding this mod, having trouble coming up with anything using the search engine.
Thanks.
Mike P.

 

[Agnem]

Welcome to the site. Please DO read our FAQ's at the top of the forum, and acquaint yourself with the various articles in our Technical archives, which is where you would have found this mod.