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Ok so my 94 Toyota pickup 3.0 4x4 auto efi fuse melts but does not pop when I use my ac and it only happens when using the ac. I normally drive without using my ac and the fuse does not melt and does not give me problems when driving but when I use my ac for for more than 20mins I notice that the fuse plastic part will melt but not blow. After using ac and I park truck for a bit let it cool I go to start up and it gives me a sputter problem like it's missing but when I blow the gas it's fine until I come to a stop and when I take off it sputtered again but only on take off or idle. So I'll put a new fuse in and all is good until I use ac. Also where the fuse is located it's alittle melted where fuse plugs in. I've check all grounds and even added an extra ground but still does same thing when using the ac. I'm thinking of opening it up tomorrow and look under fuse block just to see if anything is wrong or burning. Also going to upgrade the positive wire that feeds the box. Any info on to where I should look would greatly be appreciated. Thanks
I agree with akwheeler. Check how well it fits in the terminals. Is this a common occurrence or did it happen once and you made the post. If it was a one-time thing it could have been a faulty fuse but not likely. The way a fuse works, it has a certain resistance and cause the conductor inside it to melt at a certain current. If there's is more resistance than the fuses conductor anywhere else in the circuit that location is going to be the weak link and generate the most heat. In your case it looks to be where the fuse contact meet the terminals. If they are dirty and corroded and loose they will cause this problem. Could also be a loose connection between the terminal and it's actual wiring.
How well does the fuse fit in the terminals and are they clean? What size fuse are you using? Does it happen instantly when you turn on the AC or does it take a while (how long)? Does it make a difference what setting the blower is set to? Does it do it when you use the heater only? Does the harness to the fuse box get hot or even a little warm?
Look into some of these and diagnose them. It's hard to give you just one straight answer. Everythings gunna be different so we need as much info to work with as possible.
It only happens when I use ac for more than 20mins and ac alone I checked the lines and the battery positive get warm and I use the fuse recommended. I opened it up today and cleaned everything up. I know that the efi relay gets hot and that normal but I've never run into the fuse melting like that and not popping. I've checked all grounds and even cleaned it off and added a new ground but I've yet to test it after I did all of that. I will post up any new information after I test it today.
That's a tuff one. You say the battery it's self is getting warm or just at the terminal? Sounds like a loose or dirty terminal or internal broken battery there. But, if those are bad enough that running the AC pulls enough current to make them hot then they really shouldn't even be able to put out enough current for the truck to even start. That still sounds unrelated to the melting fuse. How about where the main battery cable goes into the fuse box? Look good? What brand fuses are you using. Perhaps you got some bad one's. No fuse should melt.
Do you have a multimeter you can measure exactly how much current is actually being pulled. It would much easier, quicker, and safer to track down what's pulling current with one however most max at 10 amps which may not be enough. I think the big step is figuring out what's pulling so much current or even if anything really is. It could still just be an issue with the fuse block. If you can't measure current at least try measuring for any voltage drop
Theoretically the best way to measure drop on the fuse is to touch the probe on the small metal tab on the top of the probe. When current is close to the max of the fuse one side should show a bit lower than the other. Try measuring other places for voltages. Everything should be pretty close to running voltage. Check voltage on all the fuses, the battery the battery cable going into the fuse block, compressor clutch. Pretty much every where. Check grounds too. Put one probe on the positive battery terminal and check voltages on ground wires within the AC and ecm electrical.
Here's a diagram for the AC circuit to help you out a little
07-30-2017, 02:09 AM
