Weird Electrical Issue... Help Me Fishexpo101, You're My Only Hope

K_Watson

1998 Prizm 3sp 127,000 miles

This is a stumper. Car ran fine all morning while running my errands... It's been fine for 7 year, besides A/C comp. and a starter (both fixed)

I stop at goodwill for a 1/2 hour and come back out and it stalled when I tried to put it in gear to leave.

If you start the car the tach jumps around for a second and the brake light illuminates, but the handle is down and the fluid is clean and full, then it will sometimes quit (not die, just shut down as if the key was turned off) and the small black relay on the lower drivers side relay panel will go crazy.

If it does run it runs 90%, there's a little something off, a little variation in RPM that is not normal for the car before today, and is seen in the video... If you give it gas it will run fairly smooth. one time today it reved up and down on it's own while gas was held, but just that once.

The weird parts...

If the car is off and the key is out and you pull the turn signal lever to passing lights, one of the radiator fans comes on and stays on until you turn the key to "on" and then off. This is repeatable.

The bright indicator light and turn signal indicators are dimly lit - this is every time

The BRAKE light is on when running, yet brake is off - this is every time

If you turn on the a/c, the engine RMP rises and compressor partly engages but doesn't have enough pull on the clutch to turn the compressor - this is repeatable

If you turn the blower up to 3 or max, even with the A/C off, the car quits - this is repeatable

I know what you're thinking... but it's not the A/C, it's off in the video.

If you put it in gear it quits. - this was repeatable, but I was able to move it a few feet one time I tried.

If you turn on a turn signal, it and the BRAKE flashes fast and the car quits

Wipers and sprayer work fine, no effect on car

If you turn on the brights, they don't come on

It will run happy for a bit then quit

Some times it will just run happily until you turn it off, but it you do anything listed above it quits. This is repaetable

I disconnected everything i have added like the remote starter, but it still acts up.

WHAT I'VE DONE TO THE CAR

Air Conditioner - 2009 - works fine

Remote starter - 2009 - worked this winter lost fob - wiring looks fine - now disconnected

Stereo - 2010 - Works

Larger 34R AGM battery -2011 - Tested Good last week

Subs and amp for front stage 2010 & 2011 - Works

BIG 3 all in 4 gauge - 2011 - soldered terminals, amplifier, additional alternator power wire, and body to engine and engine to ground wires - clean tight, no corrosion or rust

driving lights - april 2013 - works

Full cluster and Ambiant Air Temp Sensor from Corolla with original Prizm Speedo / ODO - July 2013 - works

*** The car was torn apart to diagnose, it was whole when this started. ***

FISH? Help?

No expert here..but i'd check the ground strap..they've been known to corrode badly, especially on Prisms

K_Watson

Turned out to be a burned up ground junction named either "ID" or "J8" in the scematics, which is under the dash near the break pedal. Sometimes it's failure takes the DRL module with it, but mine appears undamaged, but I won't know until the ground is fixed and the car is tested

K_Watson

Update. A mechanic friend cut up the harness known as either "J8" or "ID" and wired in a salvage harness and I was back on the road again...

Until today.

The problem is returning. The "new" harness is getting hot and the car will quit if it is disturbed.

What is the usual cause of this to getting so hot and burning up?

friendly_jacek

Shorted?

I'll have to look at a schematic - but I'm with friendly_jacek - there is a short somewhere in the line. Lots of the wiring for the car are redundant - so it will very time consuming to buzz out each lead and trace it down.

Since you've identified a line that is physically getting hot to the touch - you should be able to visually follow it to the function point. See if there is any point where the wiring is touching the chassis - could be the insulation on the wire chewed off, or wiring might be too thin/splice point having too much resistance.

Could also be a current limiting issue - you have a lot of additional accessories on the car. Might be useful to see where the peak current loading is with those accessories running. Could be one of them is loading down the car. The alternator may not be able to keep up - that stresses the electrical charging system which can lead to some really weird electrical issues.

This is definitely a tough one - your car is acting almost like a project car I saw that was flood damaged - all sorts of weird electrical issues from that one, ended up just parting that one out - as almost every single electrical junction point on that car was FUBAR.

K_Watson

Fish...

My mechanic solved it this time... I hope.

I drove the car and idled at his shop (about 1/2 hour total) with heater, defroster, and the sound system running and the harness would not even get warm until the low beam headlights were turned on. DRL's alone did not heat it up enough to notice.

He traced the one wire that was getting burned and it turned out to be the ground wire out of ground junction to the body. He removed the blue cap from the junction, cut off the blue casing off and removed the metal junction piece and soldered a 12 gauge wire to the bare metal strip, grounded it, and plugged it back in. He then cut the burned wire off the harness.

The junction now stays cold and the car is back to normal operation. I checked several other wiring masses and found no warm wires.

I DID FIND on a 2002 Corolla at the salvage yard, with a very different harness in place of the one found on earlier vehicles. this one had the insulation stripped back and the bare wires fused together by compression and heat until they made a solid block, that block was capped by a rubber dome and tapped with yellow electrical tape identical to the kind used on Toyota air bag systems. It seems like a last minute design modification at the factory because I know no mechanic with a device to make that kind of junction with the wires still in the vehicle