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Any Electrical Superheroes? Tap brake pedal = no electricity

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
Okay.
3 months ago I installed Megasquirt with my own harness.
2 weeks ago head unit maybe the amplifier to the sound system would flicker (causing loud pop in speakers).
1 week ago car starts randomly shutting off when braking for an intersection (lose electricity). Every powered object on the car would go dead for random amounts of time, then just turn back on, after a millisecond or 5 minutes and all would be fine until the next incident.
3 days ago, I go to pull the car out of the garage, successfully unlock car with alarm remote, hop in turn on megasquirt and zeitronix (on one channel with MPI relay) go to crank the car and all dash lights go out and everything shuts off.

Thinking short in my custom wiring harness right? immediately remove the whole harness and turn key to on and have no power.

I have a relocated battery (to trunk) with 0 gauge wire running up to the factory battery terminal spot and the 5 gauge or similar ground connecting to the shock tower in rear.
check voltage drop and continuity across those and all is well.

I disconnect the power at the factory battery terminal fuse box and find I have one continuity to ground, at the white with red stripe wire which goes to seat belt, sunroof (don't have) and defroster, then also to the fuse box under the dash with fuses I believe 6, 13,14,15,17. I pull fuse 17 and continuity to ground is no longer present. Leave fuse 17 out and put the rest of the car back together and still have no power. Here I throw wrenches, kick the neighbors cat, and begin to cry and masturbate using my own tears as lubrication.

Today I try to repeat the test with fuse 17 and it shows no continuity to ground... WTF?!?!?!

Is this a short? Is it a bad ground? Where do I start? Should I just strip the whole car down and put a carb'd V8 Hemi in it?

Please help with some direction...


PS the batter is fully charged.

PPS amp draw between the neg and the neg battery post was to the tune of .017 amps

Thanks. Erik
 

Hertz

Staff member
Joined
Jul 29, 2002
Messages
13,501
Location
Chicago, IL
Random loss sounds like a corrosion/connection problem. The braking system (lamps, ABS crap) pulls a lot of amperage on our cars, perfect time for the juice to cut out.

I fought this for years. Clean all the terminals really well, everywhere. Shake any efflorescence out of the fuse boxes, etc. Put everything back together right and tight. Use dielectric grease.
 

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
Thanks Hertz... I will go clean some stuff up. One more thing to add... I have removed the abs pump and computer. most of the wiring is still intact, but I would imagine that should not be a problem.

Question: Does fire extinguisher "powder" conduct electricity? long story but there is some in one of my tail lamps... lots of it.. not relating to any electrical problem or fire either. hmmm....
 

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
Well wasn't the fire extinguisher gunk...

Just for further info... I unplugged the tailights to see if there was any change and there was not.

Thanks
Erik
 

iceman69510

Turn Right Racing
Staff member
Joined
Mar 5, 2001
Messages
10,931
Location
Michigan
Where did you unplug them? It could be a short across a bulb base itself is why I ask.

I had this similar symptom years ago on a car and it was a bad ground under the dash. Because of the amp draw of the tail/stop lights, when I hit the brakes it would shut down all the dash lights.
 

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
I unplugged them at the housings... so the entire lamp assembly was disconnected. IE only the harness was left connected in the system.

I am starting to wonder if it could be as simple as a short in the brake lamp assembly. I was also thinking about inspecting the switch really well... I don't know if a bad switch could cause a short? seems a bit hard to believe.

This is so frustrating... but I am trying to just keep it simple and think it through logically... if I am noticing the problem when the brake is pushed, maybe it makes sense to look there right??

I will be back at it tomorrow. Thanks for the replys and I will appreciate any others.

Thanks

Erik
 

Wizardawd

Well-known member
Joined
Aug 7, 2007
Messages
1,323
Location
Franklin, NC
+1, I had the same issue when a battery had a bad cell. Would read 12volts, but under a load would drop to under 8 volts.

Wiz
 

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
"PS the batter is fully charged."

Yep... it was reading 12.7ish when I first checked... And I also did try another fully charged battery just in case that was only a surface charge.

Not a bad question though...

Thanks
Erik
 

Your problem has to be either dirty terminals on the battery, or a bad connection where either the ground cable connects to the chassis or wherever it is that the positive cable connects. If the problem was a short you would be blowing fuses or melting wires. #1886 had that problem when I first bought it. Sometimes I would hit a bump and lose all power. It was just the battery terminals.
 

91GSR

Well-known member
Joined
Sep 10, 2008
Messages
728
Location
Newport News, VA
dont forget the alternator either...i had this problem for a while when i had my stereo turned up a litle too loud and hit the brakes the car would shut down. the engine would still run but everything would come back on right away. turned out my alt was bad.
 

misterfixit

Well-known member
Joined
Aug 4, 2004
Messages
1,583
Location
Midlands, UK
hI SOUNDS DUMB, BUT HAD 3 CARS DO THIS... sorry for the caps.. Cheack the tail stops light bulbs for shorts. (pull out all 6, 2 in each cluster and 1 in each side of the trunklid) Had it in a sunny, a peugeot 605 estate and a toyota where the two filaments were touching and t would be fine till you press the pedal then boom fuses out.

Rich
 

89coltgt

Well-known member
Joined
Mar 14, 2006
Messages
1,027
Location
Ste Genevieve, MO
I am with Jeff O on the crappy ground/positive connections, that is what it sounds like to me.
 
Last edited:

DSMTurbo2

Well-known member
Joined
Feb 13, 2005
Messages
261
Location
Traverse City
Way to go Jeff!

Well so I took some voltage readings at some various locations under some load this time. Turned headlights on defroster radio etc... Read voltage at the battery posts and received a reading of 12.57v so I went on into the engine bay. I took another reading at the end of the 0 awg power supply cable that was run for the battery relocation and where that cable meets up to the factory battery terminal I receive a reading of 3.57v under the same conditions. Hmmm whelp...

I got the rear and begin to remove the fused distribution block right next the battery in the trunk. I remove the 0 awg input wire from the block... looks really clean, with no forms of corrosion or anything... hmmm. I remove the output side 0 awg wire that run to the factory battery location and find something odd. Upon close inspection I see that the distribution block has a significatly smaller output hole than the input and that the 0 awg wire has been cut away significantly (tards). So I go look up the part number on the distribution block and find it to be a stinger audio fused distribution block with (1) 0 awg input and (2) 4 awg outputs...

Amazing... So the yahoo that did the batter relocation spent all this money on 0 awg wire only to cut it away and essentially make it 4 awg wire that has some how made it about 6-8 years before I believe essentially melting itself slowly and is now cracking inside the housing and breaking apart... I have hear to go with a minimum of 2 awg wire when doing a battery relocation, so 4 awg was probably not sufficient.

I moved the batter back to the front of the car, hooked it up to the factory power side and ran my ground and the car turns on, powers everything up, and runs like a dream.


Off to do this project again right! 150A circuit breaker and some proper 0 awg wire.

Thanks everyone for the replies.

Erik
 
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