Since last summer my truck keeps blowing fuse 26 and then I have no reverse lights. If I replace the fust its ok for a bit but blows again the same day sometime. The book says its the fuse for revers and overdrive. The overdrive button on the tree shifter stops working too but the truck does not seem to be reving any higher so I think the overdrive itself is fine. Anyone have any ideas on this issue? I can't find the short but its got to be shorting somewhere...


Thanks

Chris

 

overdrive is just the lockup tourque converter to my knowledge. It's not but a 200 rpm savings, so the sound might not be terribly different. Try putting in a new fuse in on the way out to somewhere and note the rpm on some stretch of road, then pull it out and note the rpm at the same speed. this will ket you know if it's both you're losing. I'm guessing that you are.

As for the short, I would start at what's simplest. Look for power to ground in the reverse circut. Once that is ruled out, then you can focus on finding the place in the overdrive circuit that makes the short or fix the short you found.

It also helps to know when it blows. If you are always reversing when it does then it's the reverse circuit. You can test this with a smaller fuse. Try 5 amps or so less. Then put it in reverse and see if it blows, then try overdrive and see what happens. As long as the amps are close between your test fuses and the real ones they shouldn't blow with normal draw.

 

The most likely suspect is a bad bulb or bad bulb socket. Try removing the reverse lamp bulbs.

Then the next most likely suspect is the reverse switch itself since power is feed directly to the switch and then out through it to the rear lamp. In most Ford vehicles it bypasses the directional switch.

It is usually run near the driver's side exhaust manifold and usually has enough slack so if a wire tie lets go it can fall on either the hot manifold or hot exhaust pipe and ground out through that. Though usually it is just a defective switch on the transmission.

 

Thanks for the help guys. I put a 30 amp fuse in before I went to work yesterday and when I reversed out of my driveway it had already blown. I will try removing the light bulbs and see what that does. How do I check for power to ground?

Thanks again!

Chris

 

Well disconnecting the bulb sockets did not help the fuse still blows. I also put in a fuse when I had the truck already in drive and it blew as soon as I put in the fuse. It does not blow if the truck is in park and I put in a new fuse though.

Any other suggestions? This one is a mystery to me!

Chris

 

Are we talking about your 98 B-4000 SC????

If it's a auto tranny model, look to the neutral/start switch on the tranny.

 

Do you have a towing receiving and associated trailer wiring? Check that for shorts, too. Everytime I plug a trailer in on my truck, it blows fuse 26. Once it's plugged in, it's fine. I'm too lazy to figure out what the real problem is (static electricity buildup feeding back through the wire?). I just pull out fuse 26, plug in the trailer, then put fuse 26 back in.

Long story short--something in the towing wiring may be causing the problem.

 

Yes we are talking about the 98 b4000. I dont think its the trailer wiring just becuase its fine when I put the truck in reverse but when I shift into drive it blows the fuse. It is an automatic. Where would I find the nuetral switch? My repair manual does not show anything for the tranny.
Thanks,
Chris

 

Well after thinking about this some more & re-reading your posts about when the fuse blows, with the OD solenoid on this circuit, it should be high on the suspect list too.

So, if you look at the dash indicator & you push the OD switch, so the OD OFF illuminates, does the fuse still blow, when you put it in drive????

 

I have a 2001 F-150 Supercrew Cab and I have been blowing fuses for about a month. Truck will run well for a week or so and then I start having problems. When the fuse/fuses blow I can't get out of park and have to replace a fuse. I think it's number 11. I've never had a problem with the truck until now. Any ideas?

 

That is actualy what I tried yesterday before I went out. I replace the fuse and started the truck. Then I pushed the OD off button on the shifter tree so OD/OFF showed on the dash. Then I shifted into Drive and it blew again. I defenitly think its something with the overdrive but what is the question. I have found some other posts where people were having this issue but no solutions....

Thanks

 

Ok, then disconnect the electrical connector from the OD solenoid & see what happens.

If it still blows, try disconnecting the N/Start switch on the tranny.

Seems to me, one of those should help isolate the problem a little more.

Let us know what you find.

 

Thanks for the help Pawpaw. I will try both of these but can you tell me which conenctor on the tranny is the nuetral switch? I noticed a few when I was under the truck the other night. Also, where is the OD solenoid located?

Thanks again for all your help! I hope I can finaly figure this one out.

Chris

 

Which tranny do you have???

 

Its the 4.0 liter model so I beleive its the 5R55E tranny. The manual says all the 4.0 models have that one.