PDA

View Full Version : Finding an Electrical Short



crymson
03-25-2012, 04:57 AM
It's nearly time for me to start cleaning and fixing up my Gen 5 and decide whether to sell it or keep it. But first, the fixing. One of the reasons I bought my Gen 7 is that there was/is an electrical short in the Gen 5. About the time I stopped driving it i discovered that I had the wrong battery in it, one much to small. Replaced it and all seemed good. Until a few weeks ago when I pulled and charged the battery and found it wouldn't take a charge, at all. I said, okay, it's sat for almost 2 years, I can accept that. Went out and got the cheapest battery that my favorite auto parts store of the moment had, slapped it in, and she started up happily; but the battery light didn't go off. "Uh oh" I said, "I've seen this before". Pulled the alternator off, took it back to same shop. Dead. Third one down since I bought the car in '07. This leads me to believe that it's grounding out somewhere, but I have no idea where. First thing was to pull all of my own work. Disconnected the amp battery side, and then the head unit, still no luck. I know that the guy I bought her from didn't treat her real good. He defiantly had an aftermarket stereo in her, and what I think are rocker switches he used for NOS (this car defiantly has been swapped from one 5S-fe to a different 5S-fe), so I'm pretty sure that he screwed something up either in the initial setup or in the removal of all of his stuff.

How do I go about testing this? My first thought is to pull all of the non essential fuses (thus narrowing down the number of paths for a short), and see if it's still shorting. If it stops shorting how do I test the systems I'v unhooked? and if it doesn't stop shorting, what's the next step?

l0ch0w
03-27-2012, 03:09 AM
This sort of sucks, but its quite common for there to be shorts in the wiring where the alternator wiring, A/C wiring, and O2 sensor stuff all cross near the exhaust manifold...

I might suggest just replacing the whole engine harness, and go from there...

If you want to really go at it, youre gonna have to use a DVOM to troubleshoot... I suggest you hit up the BGB page and learn how to read the wiring diagrams...

crymson
03-27-2012, 05:26 AM
I do know how to read wiring diagrams, I've soldered devices from the PCB up, but I'm just not real versed in troubleshooting. I'm really hoping that I can trace this down to some of the work that the previous owner did, his method was twist and tape.

I can do the whole harness, I was just hoping to avoid that. Sigh.

crymson
03-27-2012, 07:24 AM
Does anyone know if there's a part number for the engine bay harness? or do i need to just go find one in a salvage yard?

Hipster Lawrence
04-03-2012, 01:17 AM
First thing is a good visual inspection. If some hack hacked it it will usually be obvious.

3 alternators in a row in my experience is almost always a result of buying cheap remanufacutured parts from autozone or whatever. If it doesn't say Denso on the box don't buy it.

crymson
04-03-2012, 07:25 AM
guilty as charged.

93celicaconv
04-13-2012, 04:05 AM
Go to an automotive parts store that checks batteries, alternators, starters, etc., by connecting their device right to the car (provided you can drive it there). That will tell you a lot, especially if your alternator is acting up, or if you have a high parasite current draw (there is always a very small parasitic draw due to the ECU, radio head, and other items that depend upon memory to keep it. If you have a high parasitic current draw with everything turned off, then you have a problem somewhere. Be aware that frequent use of a high current amp on a stereo system on an alternator that can't keep up with the current demands of such a system will fry an alternator fairly fast. The Celica alternators from generic parts stores are particularly vulnerable. So if you have no parasitic current draw to speak of, you may be killing the alternator from how high a volume you put on your aftermarket stereo/amp.

crymson
04-13-2012, 06:01 AM
I found it, it was an aftermarket alarm system that had been hacked into the system, was drawing ~1.3 amps all the time. Funny thing is, I've had my car for five years and never even knew about it.