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Discussion Starter · #1 ·
i put this in the general mk3 section too but this section seems better, so here it is again...

I bought an 88 supra turbo knowing it had this problem and i've been working on it with circuit diagrams for a month. a voltmeter will read 12V when connected between the chassis and battery neg terminal. i checked the fuses and none were blown. I can get the chassis down to about 0.3V only when I remove ALL of the following:

interior- stop fuse, dome fuse, power equipment breaker
exterior- haz/horn fuse, EFI fuse, Radio#1 fuse, RTR fusible link, and unplug the alternator

The car WILL run with the chassis at 12V, but i don't like it. my battery gets run down plus my alternator was fried, so i bought a new one but i don't want to put it one until the 12 volt chassis goes away. all the connections look good. i have no idea what the problem is, if anyone can help i will be forever indebted to u.
 
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sounds like u got ahuge short problem. u gotta trace all the wires in the cab
find out which ones are shorting usually around the chassi edges
through holes and such
 

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Discussion Starter · #3 ·
hey thanks, i thought it was something dumb like that. Do you think I should take off the dash? or is that just a total pain in the @$$ and i should take it to a shop?
 

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taking a car to an electric shop can be very costly if they dont really know what they are doing so be cautious on where you take it.
 

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I would probably, time permitting, sit down with my TSRM and start testing the harnesses at the junctions for continuity to ground.

Yeah, taking it into a shop can add up VERY fast when it's an unknown electrical problem.

Do all of your electronics function properly? If anything's not working, or for example if the dash lights are always dim or are always bright and don't dim, I'd start there.
 

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Are you getting the 12v reading with the neg lead connected or disconnected on the battery?If its connected try replacing it or making sure the mounting points are clean and make good contact, no rust dirt or grease on the block connection .clean the battery post and terminal if its a clamp on terminal make sure the wire and mating surface is clean.
 

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Discussion Starter · #7 ·
thanks for your input, to clarify: the chassis is 12V with the + terminal hooked up. When i connect the neg terminal to the chassis it's like putting 12V right on there...sucks the juice right out, not good. The battery terminals are clean, and the car runs, but only until the battery runs out of juice.

Anyone know where I should look for shorts? there's wires all over the place. what's a wiring harness? looks like i've got tons of wires grouped differently and running into the cab, around the front, to the engine, everywhere!

If i just get the fuel pump short fixed i can at least drive it to the shop if it comes to that.
 

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Anytime I have seen a short like that, I also found the short by sound, smell or open flame.........If you can pull fuses and make it stop, start putting them in one by one using the factory specified amperage fuse and you should be able to narrow it to a circuit or group of circuits. Have you removed the wires from the alternator to rule out an internal alternator short? Check any wires around the exhaust system, they can sometimes melt to the pipe and cause a short.
 

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Have you treied this with the bad alt. disconnected?If the alt. fried bad enough it could be internally grounding out. You mentioned a short on the fuel pumpIn your 2nd post?
 

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Discussion Starter · #10 ·
^ yeah i think there's a short somewhere between the battery and the fuel pump because the EFI fuse separates them. When I take out the EFI fuse (AND ALL THE OTHERS) the 12 chassis goes away.

i think i remember plugging in ANY of the items on my list (first post) would cause the short, including the alt. so there probly was an internal short in the alt. It just stopped raining here so I'm gonna go outside and confirm all this then i'll get back. btw...thanks for all your help!
 

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Discussion Starter · #11 ·
I just found there's another short and spend an hour trying to find it. It's right below the fuse box, but I'm sick of messing with dirty old wires, i'm gonna take it to a shop. Do you guys recommend the dealership, local garage, or local auto electric place? how much should it cost, 500-1000 ...or more? I don't think i want to spend more than a grand.
 
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