1987 Toyota Pickup 22R auto 2-wheel dive. Simultaneous failures of overdrive and windshield wipers. I took it to a shop and they couldn't find the problem. They did find a circuit with a "direct short": a fuse would instantly blow on replacement. I'm lost on this. HELP!

 

Uh, which fuse?

My electrical diagrams are for a '94, but the windshield wipers are on the ... Wiper fuse.

 

I'm pretty new at fixing these trucks, but I had a similar electrical problem when I was rewiring my 4runner's rear window motor, so I'll try to help out.

A short that'll immediately blow a fuse is usually caused by a "hot" wire's insulation being cracked or worn through while touching the body, frame or some other grounding point before it reaches the intended component. This completes the circuit too early, sending the current back through the ground which "shorts" the circuit and as you know, blows the fuse. Without the fuse, much worse things could happen!

Do you have an fsm? Get one if not. Same with a multi-meter. Check the wires from your main fuse box to the affected components and I bet you'll see somewhere that the insulation looks damaged (cracked, frayed, worn or burnt insulation jackets can all do the trick). This is most common where the harness passes through the firewall, so check the rubber boots, and wires there first.

 

Does your truck have Wiper Delay? If so there is a green box in the passenger foot kick panel. Pull the green box out and look on the back side and see if the cover is melted. If this is the case, some trucks came without Wiper Delay and the green box can be removed along with the factory jumper wires you see below and connect the factory connectors without the green box. This is not a hack fix but the way Toyota sold trucks with or without Wiper Delay. Most common problem I find on wiper issues is the delay box. I would check the combo switch and motor as well.

Where my thumb is going to be melted and you have to pull it of the kick panel to see the back side of it.

 

Thanks, Terrys87. I don't have wiper delay but I'll look for the box later today. How would this involve the simultaneous failure of the overdrive?

 

If you don't have wiper delay, it is not going to be a problem for you. Not sure on over drive and if it is related to your problem. I was just going by the most common problem I see on wiper issues.

You are going to have to let us know what fuse blew. Get on that circuit and most likely there will be a few other things on that circuit and start trouble shooting each circuit on that fuse. Electric is my weak area.