Electrical question.

2305 Views 66 Replies 12 Participants Last post by Snulma1, 7 mo ago

Snulma1

Discussion Starter · 8 mo ago

I have an electrical problem I’m trying to wrap my head around.
Dissasembled my dash to replace my gauge cluster, redo the radio, repaint, and then replace my heater core and wiring.
Swapped out the gauge cluster, and tested the lights with them all working. Then plugged back in the wiper switch and seated cluster as well as screwed in.
Went to check the cluster one last time and they lit up but then went dark.
Thought that may be the battery was low, so pulled it out and placed on a charger for two hours. Placed back in and the lights lit up and the wipers worked but then everything clicked off again.
I’m assuming there’s a short somewhere but not sure where to start. Does anyone have any suggestions?

41 - 60 of 67 Posts

Snulma1

Discussion Starter · #41 · 7 mo ago

Woodchuck said:
Exactly WHAT stops working properly when you have your issue? Just the instrument cluster illumination or more?

The marker lights and the cluster don’t work when the headlights are on.

Woodchuck

· #42 · 7 mo ago

Snulma1 said:
The marker lights and the cluster don’t work when the headlights are on.

When you say "marker" do you mean the front side marker lights or the front parking lights? The front parking lights do NOT work with the headlights, only in the "PARK" (1st) position. If the cluster lights work in the "PARK" position but shut off when you pull the switch to the "HEAD" position then either the switch is defective or the plug is wired improperly.

Snulma1

Discussion Starter · #43 · 7 mo ago

Woodchuck said:
When you say "marker" do you mean the front side marker lights or the front parking lights? The front parking lights do NOT work with the headlights, only in the "PARK" (1st) position. If the cluster lights work in the "PARK" position but shut off when you pull the switch to the "HEAD" position then either the switch is defective or the plug is wired improperly.

Sorry I meant the parking lights.
So since the cluster turns off when in the head position, and we tested the switch and it has the proper continuity it must be a wiring issue right? Any tips on figuring out where the issue lies?

Woodchuck

· #44 · 7 mo ago

Snulma1 said:
Sorry I meant the parking lights.
So since the cluster turns off when in the head position, and we tested the switch and it has the proper continuity it must be a wiring issue right? Any tips on figuring out where the issue lies?

Check that the BLU/RED wire is properly located in the headlight plug in the slot matching up with the "I" position. If it IS, examine the rheostat and its contacts that something isn't moving when the switch is pulled out all the way.

Snulma1

Discussion Starter · #45 · 7 mo ago

Woodchuck said:
Check that the BLU/RED wire is properly located in the headlight plug in the slot matching up with the "I" position. If it IS, examine the rheostat and its contacts that something isn't moving when the switch is pulled out all the way.

Rheostat makes good contact through CW and CCW rotation and into contact point. I looked at the Blu/Red wire and it’s seated properly with a clean contact point.

Em1ssdv

· #46 · 7 mo ago

If I follow the discussion properly, you have an open in the wire somewhere in the highlighted area. Disconnect battery cable, with headlight switch on you should have continuity (almost 0) between A (or B) and R. Where are you located? depending on where you are I or someone I know may be able to help you. I'm in NC.

Rectangle Slope Font Parallel Number

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Snulma1

Discussion Starter · #47 · 7 mo ago

Em1ssdv said:
If I follow the discussion properly, you have an open in the wire somewhere in the highlighted area. Disconnect battery cable, with headlight switch on you should have continuity (almost 0) between A (or B) and R. Where are you located? depending on where you are I or someone I know may be able to help you. I'm in NC.
View attachment 865889

Just to make sure I understand, if I use ohmmeter on the wiring harness for the light switch and test between A(or B) and R I should have continuity?

I live in northern NJ. Anyone near and willing to help would be appreciated!

Woodchuck

· #48 · 7 mo ago

Em1ssdv said:
If I follow the discussion properly, you have an open in the wire somewhere in the highlighted area. Disconnect battery cable, with headlight switch on you should have continuity (almost 0) between A (or B) and R. Where are you located? depending on where you are I or someone I know may be able to help you. I'm in NC.
View attachment 865889

What does "R" have to do with things? That's the rear tail lights which, I believe, work fine. I though the issue was the instrument cluster lights, which is "I", and which the OP already tested, above and which stop working with the switch in the "HEAD" position even though a "bench test" shows continuity.

Snulma1

Discussion Starter · #49 · 7 mo ago

I’m still at a loss. Looking under the dash there are definitely a couple of wires that are unplugged, don’t know if that’s the issue, hard to trace many of them.

Woodchuck

· #50 · 7 mo ago

Snulma1 said:
I’m still at a loss. Looking under the dash there are definitely a couple of wires that are unplugged, don’t know if that’s the issue, hard to trace many of them.

Colors?

INTLgunMonkey

· #51 · 7 mo ago

Snulma1 said:
I’m still at a loss. Looking under the dash there are definitely a couple of wires that are unplugged, don’t know if that’s the issue, hard to trace many of them.

If most of your wire harness is original, the color coding is well documented, and can save you a lot of time.

Before you go moving wires around, though, I’d try to clean the switch. It’s a really robust, old-school-tough part, but it’s had over 40 years to corrode. Mine was doing a similar, but not exactly the same, thing as yours, and it works perfectly after a cleaning.

Get a can of this-

www.amazon.com

Amazon.com: Hosa D5S-6 CAIG DeoxIT 5% Spray Contact Cleaner, 5 oz. : Automotive

Amazon.com: Hosa D5S-6 CAIG DeoxIT 5% Spray Contact Cleaner, 5 oz. : Automotive

www.amazon.com

Pull the knob (there’s a spring-loaded button on the passenger side of the switch body that releases the knob to come all the way out).

Give a 1-2 second shot directly in the hole you pulled the knob out of, and then another 1-2 second shot on the rheostat path - you’ll have to pull the instrument cluster to see it, it looks like a long coil spring mounted on about half the circumference of the white plastic tumbler that rotates when you turn the knob.

As soon as you spray those two parts, spend a full minute or two pulling the knob in and out and rotating it through its full travel. Don’t skimp on the full minute or two, you’re scrubbing the contacts on each other and it needs the time and repetition for the solvent to work.

Wait a few more minutes, hook the battery back up and give it a try.

That Deoxit is made for exactly this sort of part. I’ve used it to fix “broken” 50 and 60 year-old guitar amps that just had corroded contacts.

It may not solve your problem, but it’s a good, safe place to start.

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CJM68GT390

· #52 · 7 mo ago

You will find this very helpful:

ELECTRICAL ASSEMBLY MANUAL, 68 MUSTANG - #L-33E - National Parts Depot (npdlink.com)

Snulma1

Discussion Starter · #53 · 7 mo ago

Woodchuck said:
Colors?

Here are the main ones I see.

Hood Automotive tire Motor vehicle Finger Bumper

Automotive tire Motor vehicle Bicycle part Grey Automotive wheel system

White Light Material property Bag Gas

Headgear Bicycle tire Automotive tire Motor vehicle Auto part

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4

Woodchuck

· #54 · 7 mo ago

Cleaning the crud off the wires may help a little....

Snulma1

Discussion Starter · #55 · 7 mo ago

Woodchuck said:
Cleaning the crud off the wires may help a little....

I’ll do my best but it’s not crud. It’s paint since the previous owner sprayed spray paint to cover things

Woodchuck

· #56 · 7 mo ago

Snulma1 said:
I’ll do my best but it’s not crud. It’s paint since the previous owner sprayed spray paint to cover things

"Goof Off Professional" works wonders. So does GoJo (without pumice).

Snulma1

Discussion Starter · #57 · 7 mo ago

Woodchuck said:
"Goof Off Professional" works wonders. So does GoJo (without pumice).

I tried to use a Mr clean magic eraser and got this.

Gesture Finger Thumb Gas Cable

Bag Luggage and bags Eyewear Wire Electrical wiring

Audio equipment Vehicle door Gadget Eyewear Automotive exterior

Automotive tire Tire Motor vehicle Finger Hood

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4

Woodchuck

· #58 · 7 mo ago

Snulma1 said:
I tried to use a Mr clean magic eraser and got this.

Yellow is 12v hot. Blue w/red tracer are instrument cluster illumination. Could be a console feed lead... yellow for the "cubby" lamp, others for shifter illumination and ?
View attachment 866237

This "triple tap" with Black/Yellow is a switched ignition "hot" for accessories.

View attachment 866239

Black w/blue tracer are courtesy lights. Probably for the under-dash courtesy lamp(s)?

View attachment 866238

This is the instrument cluster illumination accessory tap.... accessories that need illumination with dimming capability can be plugged in here.

View attachment 866240

See notes above each photo.

Snulma1

Discussion Starter · #59 · 7 mo ago

Woodchuck said:
See notes above each photo.

Great. So none of these should be the reason for my cluster not illuminating while the headlights are on.

Woodchuck

· #60 · 7 mo ago

Snulma1 said:
Great. So none of these should be the reason for my cluster not illuminating while the headlights are on.

Sorry....

Find that red tap with the BLU/RED wires and stick a test light into it. If you get a test light but no dash lights you can assume (I know, I know....) that the problem may be the cluster connector or "printed circuit".

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