1989 Toyota Pickup, 2WD, 22R, carb. The AM1 40amp fusible link fused open one day when I was driving. I thought the ignition switch was the problem so I replaced it with a new one. I thought it was fixed and then it happened again a few days later when I was driving again. I checked all the wiring at the fusible link box under the hood, wiring, wiring under the dash, and the fuse box in the driver's side panel. I couldn't find the problem. Wiring and fuse box seemed fine. It then started fusing open the AM1 fusible link right after starting the truck and noticed that the voltage at the battery was around 12V. So I thought the alternator was the problem. I swapped it with a spare alternator that was known to be good but it didn't fix the problem. I had bought the alternator from Autozone with a lifetime warranty. I took it back so they can test it and it tested fine. They still replaced it with a rebuilt alternator. I installed that one and it still did the same. I then disconnected the plug from the alternator and the truck started fine and did not fuse open the AM1 fusible link. I connected the plug back in with the truck running and it fused open the fusible link instantly. I removed the small harness that connects between the alternator and the truck harness. I took the electrical tape off and removed the plastics to check the wires for damage. No damage found. I checked all the wires with a multimeter at the connector and found no shorts. I reinstalled it in the truck and it still fuses open the link every time I start it with the alternator connected. I hope someone has seen this problem before and was able to figure out the problem. Thanks in advance for any help.

 

Has anyone used justanswer.com for automotive repair questions. Any feedback? I'm hoping they can help me with this problem. They charge $39 a month. I would just cancel after the first month.

 

I performed a test again today. So I don't waste $7 on a 40A fusible link everytime I test, I took the top off of a blown fusible link and solder a cheaper blade fuse each time I test. I soldered in a 30A fuse today, removed the connector from the alternator, and started the truck. I did not blow the fuse. I then reconnected the connector on the alternator and it did not blow the fuse this time. I took the truck for a 5 minute drive and it did not blow the fuse. The problem is intermittent and I don't trust driving the truck since the problem should still be there. Any ideas?