• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Possible ground issue? Mystery electrical gremlin

Malicious

Well-Known Member
Local time
7:40 PM
Joined
Feb 12, 2012
Messages
786
Reaction score
199
Location
Melbourne
Hi all,

Chasing some advice on a mystery electrical problem, it maybe multiple but who knows! I’m ok with electrics, not great.

It’s got a brand new M&H harnes all through except the wiper harness.

The problems.
Heater fan on constantly.

The dome light would be on constantly if I had of used metal screws, I installed with plastic, worked as advertised.

Horn worked well, I took it to a guy to dyno tune got it back disconnected. Reconnected, now it blows constantly.

The straw that broke the camels back; I was trying out some LED globs for the brakes and the passengers side has issues. When out of the housing the one of the filaments on the twin filament bulb glows a bit more than faintly when NOT grounded to the car/housing, brighter once grounded, but won’t light up the extra filament for braking. So, no brake light on the passenger side.

I was thinking the ground might be live?

My mate that’s good with auto elec’s is MIA for the mo, so I’m going solo.

I’d love any hints that’ll help
Me track this down.

Cheers!
 
Sure sounds like back feeding due to poor/lack of ground. Make up some wires with alligator clips and start adding grounds from the body to battery,engine to battery, accessories to battery etc.
 
You definitley have some ground issues, check all your termination points first. You may need to add a supplemental body ground nearest to the battety.
Sounds like your resitor bank to your blower is shorted to ground on the blower asembley
Same thing with the horn, something is grounding out either in the column or in the harness.
As far as your taillights somewhere theres something trying to ground out...

blower-motor-schematic-wiring-of-1996-dodge-caravan.jpg
 
Had a diesel blazer (US Army) that gave me fits. Horn beeping when turn signals were on. Engine kept running with key off and headlights on- shut off lights and truck would shut off (fuel solenoid). A few other wierd things like that. It all came down to a ground wire down by the parking brake had came unhooked. Back fed juice to all kinds of places. Hooked back up and all was good. I then added a couple more grounds back to the battery/body for good measure. That one had a lot of people scratching their heads!!
 
The dim lights usually point back to grounds, but no brake light and the horn issues could be an issue in the turn signal switch area.
 
The key is, was everything operating properly prior to the new harness? With a new harness you could expect some errors. Sounds like you might have multiple issues but first, check All your grounds.
Your dome light is triggered by a switched ground. There is constant +12 volts on all courtesy lamps. Your metal screw was grounding the negative lamp wire or socket.
May not be the problem but the brake lights and horn you mentioned have one thing in common, the turn signal mechanism. There is still a difference, the lights need battery and the mechanism only passes that battery. It does not originate in the turn signal mechanism. The horn however requires ground which does originate in the mechanism/column but I still suspect the wiring.
The heater blower is relatively straight forward. Black/Black Tracer, power from fuse block to the blower switch. All other wires (Red, Dk Green, Lt Green) to the heater resistor. If it worked properly before the new harness it's probably just a connection error.

http://www.mymopar.com/downloads/1968/68CoronetA.JPG
http://www.mymopar.com/downloads/1968/68CoronetB.JPG
Don't let drawings intimidate you. If you can read a map, you can read a drawing. Your just trying to get from point A to B. All those other lines don't matter.

Good luck and keep us informed.
 
Thanks for the replies guys, unfortunately I hurt my back on the weekend. So I haven't been able to get out to the garage yet. I'm hoping to this weekend, but my Son is having his birthday party not he weekend. So chances are it might be during the week next week.

I'll definitely report back.
 
a quick note so quick update:

I haven't checked the passengers tail light out of the socket since, but I think my issue comes down to the front blinkers not being attached/grounded as I've built new ones that I'm finalising. They seem to be working fine once connected, but I haven't pulled the globe while connected to check if there is that dull glow when not grounded.

I've chucked in an LED flasher, which has helped the blinkers.

I've added a 'starter power' style ground cable from the battery directly to the body - rad/inner fender bolt.

I've pulled the glove box wiring apart - after initially getting it on road, there were more and more accessories added in, which go out of hand. So I've untangled and wrapped all the wires and I'm in the process of installing two fused power blocks (IGN and Constant) to run the accessories off of.

Had a mate help with the horn, mind you all he did was potentially burn our a spare relay! Here's some more details, I'm a little bit at a loss here:
horn blows with power - bridge purple to green.

I've stripped out all the horn components off of the column the wheel on the spun horn connector seems to spin 90degrees off from what would seem right - IE rather than turning with the wheel turning like a clock, it runs in and out of the centre of the column, if that makes sense. Looks like the rim is marked because of it, but it does look stock? no sure how I could get it to spin in the direction of the clock if that is how its supposed to go that way...

When I bridge the black with yellow tracker activate signal wire to the body of the car, and (with my limited multimeter ability) check for a circuit between the columns inner shaft and the sprung/wheel power pick up, I get a circuit. But it won't sound the horn if I bridge the two with a wire.

I've also tried hooking up another relay (4 prong - always open), as factory but grounding the forth pin (linked to the black with yellow tracker signal wire), bridging the shaft to spring pick up in the column I get no horn.

So thats where I'm at.

I will be pulling the whole dash apart soon so I can get access to everything behind the dash. I did two things behind there that I will check:
1. bolting the two ammeter connections together to bypass the gauge.
2. installing a voltmeter in the spot of the ammeter. potentially this is grounding on the dash gauge housing?

As usual appreciate any help!
 
Auto Transport Service
Back
Top