1994 Camry 4cyl Auto Electrical Woes -- AM1 Fuse Blows When Starting
 

Hello All,

I've found a wealth of helpful knowledge and assistance on this site over the years, and even some information on this particular subject, but I just can't seem to pinpoint the problem with my friend's car. Here's a rundown:

94 Camry, 4 cyl engine, automatic. It keeps blowing the 40A AM1 fuse in the interior fuse block behind the change tray when you try to start the car (ignition switched to start) you can turn the switch to the On position and everything works, but for whatever reason, that fuse likes to pop when you turn to Start. I've even had it happen a couple of times where the fuse will pop just as the engine fires up. When this happens, the engine will run, but I get nothing at the gauges, radio, clock, etc. I have the wiring diagram, and have attempted to trace the white wire that feeds the fuse in an attempt to find a short, but so far, no luck.

Things I have tried whilst attempting to isolate the problem:
- Ignition switch: New switch behaves the same way. Saved myself the $60 and returned it.

- Checking for shorted/frayed wiring under the hood and under the dash, and inside the driver's door/door jamb. I can locate where this large white wire runs, but can't seem to find any shorts or broken/exposed wires.

- Upon inspecting the fuse block behind the change tray, I did find some loose terminals in a couple of the fuse receptacles (the 7.5A ECM one was pretty bad). I used a fine point pick to bend these back into shape, and even replaced the affected fuses just for good measure. After I did this (and replaced the AM1), the car seemed to be fine. I was able to start it multiple times and test drove it, and gave it back to the owner. He took it on a couple of long drives that evening before the AM1 fuse popped again the following morning when he tried to start it.

- I did find some splices that someone made near the ignition switch connector, for an alarm system that is disconnected/no longer in use. No splices were made to the white wire in question, though.

I'm no stranger to this car. I've been fixing it for about 6 years now for two different owners. Also no stranger to schematics and wiring diagrams. I have PDFs of both the factory wiring diagram and service manual (pretty sure I found them here :) ). I've done quite a bit of work on it over the years (fuel pump, tune-up, distributor, timing belt, starter, battery, coolant temp sensor, etc.). This problem just has me stumped. Any and all feedback, questions, advice, etc. are greatly appreciated. I've seen some really knowledgeable folks on this site, and I'm hoping that maybe you can help. Thanks in advance.

So, ign key to ON does not blow the AM1 fuse but ign key to Start does.

The AM1 fuse powers many circuits. The only additional circuit with ign key to Start is the starter circuit. Once the AM1 fuse blows, all circuits powered this fuse are dead.

Check the park/neutral switch and wiring.

All valid points. The connector on that switch had gotten so hot from shorting out that I could barely get it off the switch. Once I did, I jumpered the send and receive wires for the starter by placing a fuse between their two terminals. Voila! Repeated success starting the car with zero blown fuses :) Thanks a million. You helped to ensure that this Camry will see 200k miles.

Glad to hear it is fixed and thanks for posting back with the results!

At least 200K, lets go for 300K miles.