Greetings to all. I have a 1999 Lightning I bought new.

6 months ago, I rebuilt the motor, but kept the original transmission.

A couple of months later I blew fuse 24 in the front box.
That is for the trans side of the PCM and the CMS sensor.

Along the way, I had a new billet transmission built. But fuse 24 keeps blowing at odd intervals (from 2 minutes to 10 hours).

No wiring seems to be pinched and is free to the touch. (behind the right head area and down the transmission)

Before I start dismantling the truck, I wanted to ask if anyone has a suggestion?

Thanks!

 

Start here (ignore the posts in the 2004+ threads): https://www.f150online.com/forums/se...archid=8605164

Sort through them, the answer is there.

 

Linky no workie.

I get: Sorry - no matches. Please try some different terms.

 

Hmm. WTH is wrong with the search, it shouldn't have expired that fast.

Any, do an ADVANCED SEARCH with "F24" as the keyword and fill in my user name to bring up the intended results.

 

OK, I get the idea. I have checked the wiring behind the motor, next I need to check the down stream HEGO sensors and wiring.

Thanks.

 

That would be the first place to look.

 

Here is where another member found his harness damaged and causing similar symptoms

 

Yes, that is a good spot. I have long tubes that are wrapped with fiberglass tape. The sensor wire in that area has a silicone covering.

I have already checked all of the tranny area wiring for chafing, rubbing, cuts and burns.

I am changing out all 4 Hegos, up and down stream. We will see.

 

Unlikely, but only remotely possible, to solve the problem.

 

I worked on it today, found a chafe in the lead to the right downstream HEGO made by the heat shield.......Runs fine now. (I had to remove the sensor to find it as it was a thin clean knife cut.)

Thanks for the help. I really needed a nudge in the right direction.

 

There you go, right were it was suspected...

Congrats!