Lost Power

[jann_e_gunn]

I got home today, in my 85 wagon, went inside for a few hours, come back out to find my head lights on... ah shoot. Well, lets see if she'll start.. oh yeah, brand new battery fired her right up. I think I should let her run for a few to make sure there is a full charge so I start to head back inside. A few steps out she dies. Humph. I go back to try and start again, nothing. I try to jump start.. and nothing. The head lights will still turn on, but nothing on the dash... could this be a blown fuse or breaker? The battery is about a month old, the alternator was rebuilt about the same time and she has never had any problems starting before this.
I'm kind of at a loss. Any Ideas?

[dlb]

the headlights come on but no dash lights at all, not even faint? what about the heater fan and stereo and interior light? try turning on those things and see how they are.

when you tried to jump start it, did it even crank? you might leave the second battery hooked up to the one in your car for 30 mins or so and see if that helps. i don't understand why but i have found this to be the case.

if none of that works, i would look at either the distributor or the starter.

[Petros]

Welcome to the forum,

in the fuse box under the hood (black plastic box on left side fender well), under the cover there is a square plastic fusible link that is labeled "main", that one powers everything else. see if that is good or melted. the only time I had all the electrical power off was when this main fuseable link blew when I had shorted wires. In a pinch you can wrap foil or a gum wrapper around the prongs to make it work to verify you have power, but you should find the souse of the short or you risk damage elsewhere in the system.

the other thing to check is to clean your battery terminal contacts, both at the battery end and at the other end where it either goes to ground or where it goes into the fuse box, or the starter motor.

good luck.

[jann_e_gunn]

The headlights still work, they are running on a different circuit. The 60A "AMI" fuse had blown. I put a new one in and it blew immediately. I'm assuming there is a short somewhere in the main circuit. Any ideas where I should start looking?

[Petros]

That is one of the main power supply fuses, you will have to do a detailed and careful inspection of all of the wires looking for melted contacts, 60 amps should get pretty hot before it blows the fuse.

the time I had that happen in my tercel it was the wire bundle on the left side of the engine, the one that is attached to the side of the block, had shorted. the insulation was old and cracked off and shorted to the other wires inside the plastic sleeve (you could not see it from outside). the wires got so hot they melted off all of the insulation before the main fuse blew. If that is the problem you can unplug that wire bundle from all ends, and see if fuse stays good. Than with a jumper wire and with a connector crimped on to each end jump across the connector one wire at a time until you hit the shorted wire, it will blow the fuse of course. Or you can rig an amp meter across the fuse instead and watch the read out when you test each wire to save blowing fuses.

[jann_e_gunn]

Thank you Petros, that'll be a good place for me to start in the morning.

[jann_e_gunn]

Found the short, it was right before the bundle connector heading towards the carb coming from underneath the the washer fluid reservoir. the black/red wire was slightly frayed and someone had previously fixed it with electrical tape. There isn't enough room to to do much else without messing with the connector.. Are those repairable or replaceable?

[Petros]

easy fix: you need a thin tool like a sharpened small nail (I use a dental pick tool) that you run it down the side of the connector pin to release the contact from the plug assembly. It will slide out of the plug assembly once you release the tiny tang that holds it in the plug housing. You can than either unbend the crimped end and reuse it, or find a replacement contact at an auto parts store, install it on the end of the wire (I will sometimes both crimp and solder it to make sure I have good contact), and than you insert the contact back into the connector assembly. or at worst you can remove the connector from both end of the plug assembly and just by pass it with new after market connectors for that one wire.

you usually can make one of these standard contact work in the Toyota plug assembly:

[jann_e_gunn]

Awesome. Thanks!

[jann_e_gunn]

Well, I tidied up the short and put a new fuse in and she started up and ran great. I drive her around the neighbor hood a bit and everything seemed fine. So I decide to drive over to an old friend's across town. Leaving his house the temperature had dropped and she didn't turn over on the first go, then had no power. The fuse had blown again. I check out where the short had been and it all appears good. I unplug that connector and test it at the fuse and it's getting way too much juice. I let her sit for the night and came back this morning. I hook everything back up and test at the fuse and everything seems fine. I put a new fuse in, it doesn't blow. But, the alternator started burning up at the power cable. Once again, I am very confused..

[dlb]

get it running and check what the power output from the alternator is. i wonder if its regulator is shot.

[marlinh]

You need to study the wiring diagram and find out what supplies that fuse. Are there any aftermarket add on's that could be wired funky? I have never seen an internal short in an alternator, but don't rule it out. Overcharging would not melt wires. Like Petros said, examine the wiring harness between the battery alternator and starter. You may have to wiggle wires around to duplicate the short.

Did the large wire at the back of the alternator start burning immediately after plugging in the fuse? Or were you trying to start it?

When you say the connector was getting way too much juice, what and how did you actually measure it?

[Petros]

you still have a short in the system, it is intermittent likely only coming in contact after some road vibrations or perhaps sitting at certain angle. you have to put your ammeter on it and jiggle everything. with that much power to blow 60 am fuse and melt insulation, the contact should be fairly easy to find if it is exposed. so carefully inspect all of the suspect wires and their contacts.

[jann_e_gunn]

Marlinh: I had an ammeter testing at the fuse. I was unplugging different harnesses to isolates where the short is. I think Petros is right it must just short intermitinly. I am still curious why the alternator was smoking whe the fuse was it blowing though. I'm about to get back at trying to find that short in the mean time.

[marlinh]

Don't know what to suggest about the alternator smoking. Try to find the short first. Shaking the wiring harness should mimic driving over bumps. Carefully inspect connectors for corroded or burnt pins. Check wiring where it may chafe metal. You may have to peel back the harness to check for a wire to wire short. For a draw that large it should be easy to find.

Did the alternator smoke before the fuse blew that last time? Even for a few seconds?