Electrical issue - where to begin investigating

[Ed S.]

Fired up my 64 convert (4 speed) today after a long respite from running. A new issue emerged. When running - in neutral my taillights, back up lights and instrument (dash) lights are on and the gas gauge is resting on "E" (tank is full).

The last time I ran the car I had none of these issues. The only electrical related issue I worked on was the turn signal return mechanism - after that repair - all lights etc worked as designed.

My first thought is that this IS NOT a ground issue - if it was circuits would not energize. Obviously current is getting into circuits when it should not be.

Where do I begin to investigate / diagnose the problem. Any recommendations?

[David H.]

Re: Electrical issue - where to begin investigating

Fired up my 64 convert (4 speed) today after a long respite from running. A new issue emerged. When running - in neutral my taillights, back up lights and instrument (dash) lights are on and the gas gauge is resting on "E" (tank is full).

The last time I ran the car I had none of these issues. The only electrical related issue I worked on was the turn signal return mechanism - after that repair - all lights etc worked as designed.

My first thought is that this IS NOT a ground issue - if it was circuits would not energize. Obviously current is getting into circuits when it should not be.

Where do I begin to investigate / diagnose the problem. Any recommendations?

Ed

Does stepping on your brake pedal cause your fuel gage to move?

Dave

[Edward B.]

Re: Electrical issue - where to begin investigating

Try cycling your headlight switch from off to on and back to off several times. Do the same with your turn signal lever from left to right and back to left and then to the center position.

[Frank D.]

Re: Electrical issue - where to begin investigating

Unlike the C1/C3 cars, the C2 uses a "powered" sending unit and reads fuel level via a voltage divider....so one quick check is to pull the wire off the sending unit (at the gas tank) "I" ("I"gnition) terminal and with the key on you should measure 12V; if you do not then the sending unit may well be fine and the problem is back in the dash wiring.

Exercising the headlight switch and possibly trying to get some contact cleaner sprayed in there can't hurt as suggested above.

[Ed S.]

Re: Electrical issue - where to begin investigating

Dave - stepping on the brake does not change anything, fuel gauge is still pegged on "E". I also remembered, that I replaced the high beam switch - with a used "correct" model. I tested it before installing it - it checked out ok.

Today, I turned the ignition switch to "ON" - still same problem, tail lights, backup lights, license plate and instrument lights are all on. I cycled the high beam switch - no change - I completely disconnected the high beam switch wire clip - still no change. BTW - headlights work as intended, on low and high beam positions.

I also checked the position of the gas gauge sending unit float- tank is full - float is way up there - right at the top of the fluid level.

[John W.]

Re: Electrical issue - where to begin investigating

It seems difficult to think of an issue that would affect your lights and your fuel gauge. Remove power to the headlight switch and see if that at least kills the lights. Backup lights are not controlled by the headlight switch as far as I know, they work regardless of the headlights on or off.

If there is some resistance in the fuel gauge voltage supply connection on either end all the lights being on could draw enough current to drop the voltage to the fuel gauge to cause a false reading.

Anyway I would try to troubleshoot the issue one symptom at a time.

[Ed S.]

Re: Electrical issue - where to begin investigating

Ed

Does stepping on your brake pedal cause your fuel gage to move?

Dave

No - nothing causes the fuel gauge needle to move.

Have been investigating this problem for some time - still no resolution. The problem is that all the lights in the rear (brake, backup & license plate) are either all energized or none are energized. I did some experimenting with fuses. First - all the fuses are good.
With fuse # 5 - TAIL LAMPS in (but not # 6 in):

- pull headlight knob, with key OFF - headlights work; all lights in the back ON

- turn key to ON (Headlight knob pushed in, off) – all lights in the back ON

- press brake pedal – all lights in the back OFF



With fuse # 6 COURTESY & STOP LAMPS in (but not # 5):

- pull headlight knob with key OFF - headlights work; all lights in the back OFF

- turn key to ON (Headlight knob pushed in) – all lights in the back ON

- press brake pedal – all lights in the back ON


The problem appears to be with the taillight and stop light circuits. I have disconnected the high/low beam switch, the connector under the hood near the firewall that is part of the backup light circuit, the two connectors attached to the steering column for the directional signals & horn and both leads to the fuel tank sending unit. Cannot get the rear lighting to function as intended. The issues is not that they are NOT working - the problem is they are always working. I also pulled all fuses - with all fuses out the rear lights were not energized with the ignition switch on or HL knob pulled.

The challenge is determining how energy is getting to the lights in the back - is it getting there because of a faulty headlight switch (I "exercised the switch - pulled it in and out 20 + times) or is the problem in the ignition switch, or in the fuse block - I pulled both connectors of the fuse block in the engine bay - connectors are clean, straight and firm (no wobble).

[Edward J.]

Re: Electrical issue - where to begin investigating

Ed, At one time my friend replaced his headlight switch and when he plugged the connector back in he bent one of the pins on the switch, is this possible with your switch. Have you ever took switch apart to clean contacts inside switch? Sounds like a switch problem. Maybe you can get a cheap replacement to try,or someone you know has a spare to try. Is there something up with turn signal switch? Wire grounded inside column, under column, feeding the ground circuit power to lights in rear?

[Ed S.]

Re: Electrical issue - where to begin investigating

Edward - I am also thinking the headlight switch is a possibility. I have not touched it in the past - it has always functioned correctly. Interesting, when all the circuits are energized - that are not supposed to be - including the instrument cluster lights I can adjust the brightness of the instrument cluster by rotating the switch knob. Problem is - that circuit is energized anytime the ignition is ON. RE directional circuits - I completely disconnected the two connectors that are attached to the steering column - that did not result in any changes - all rear lights and instrument lights were still ON. I have been searching threads in this forum for clues - unfortunately, nearly all electrical problems are - it does not work - or illuminate, never "always on". Power is getting to two circuits when it should not be. Have to figure out why - I am thinking HL switch or possibly Ignition switch. PLZ keep the ideas and suggestions coming.

[Ed S.]

Re: Electrical issue - where to begin investigating

Follow up - on this electric problem. To summarize - problem is with tail / stop & back up lights. All original 64 convert. Problem is - press on the brake pedal, stop and B/U lights come on - this also blows the tail light fuse (10A). Turn the ignition key to the run position - tail & B/U lights come on.

I have replaced all the rear lights with a set of new Trim Parts light assemblies, assembled correctly with new bulbs - also cleaned the ground contacts on the wiring harness (4 lights & license). Checked for damaged wires in the back - none. Also checked the ground wires with a digital meter - all good.

Installed a new headlight switch - the ceramic was crumbling on my original.

Replaced the complete turn signal system - on the steering column.

If I disconnect the 2 harmonica clips on the steering column and disconnect the Back up light wire under the hood that runs to the switch on the shifter, then turn the ignition switch to RUN (engine not running) - all the lights in the back come on including the B/U & license plate - but this does not blow a fuse. If I step on the brake pedal I will blow a tail light fuse.

How is power getting to the B/U lights? At first, based on info learned from this forum I was pretty sure it was a grounding issue - not too sure of that now.

I know it is difficult to type in a comprehensive diagnostic solution - if you would rather talk on the phone (I would appreciate that) send me PM - I will call at your convenience. Getting desperate and frustrated. Thanks

[Dan B.]

Re: Electrical issue - where to begin investigating

Considering the length of time you have battled this issue and still have not gotten anywhere, I think it would be money well spent to start by replacing the rear harness with a new one. Likely you have an internal short somewhere. Personally, I think it's money well spent to replace ALL the wiring on these cars given the age, but that's your choice. Rear harness replacement is an afternoon job.........I can't imagine living with this problem for as long as you have. With that done, it will also narrow down your issue considerably if it does not cure it.

[Ed S.]

Re: Electrical issue - where to begin investigating

Dan, that option is on the table but.... what concerns me is I am not 100% confident that the problem is in the rear harness. Might also be in the dash harness. I have disconnected the 2 harmonica connectors on the column and the B/U light connector under the hood. When I turn the key to the RUN position all rear lights come one - it appears that energy is getting to the rear harness at the bulkhead some how and energizing the entire circuit. So..... is that an indicator of a bad rear harness or a problem else where?

[Edward J.]

Re: Electrical issue - where to begin investigating

Ed, Dan is correct you have a short circuit some where, not sure what you have done lately, is your car under Resto? The rear harness runs under drivers side dash, where it then runs under the drivers kick panel, where screws that hold kick panel can pierce the harness, and then makes a sharp bend and heads under a long flat metal plate that protects harness and heads up under the 1/4 Qtr. trim, then loops over driver wheel house.there is a screw at base on Qtr. trim panel @ very bottom that possible could pierce the harness. if this problem recently arose follow your foot steps and look around those areas. Good,luck

[Ed S.]

Re: Electrical issue - where to begin investigating

Replaced the carpet about 18 months ago. Your suggestion - a screw from interior trim - is a good one. Will investigate tomorrow. Regarding the long flat metal plate that butts up against the threshold - plz refresh my memory - is that plate held in position with fasteners (screws that might violate the wire harness behind it) or does it clip into position - I recall some kind of groves that the long flat metal piece fit into. The reason I ask is I hate to have to pull up the carpet in that area if I don't have to. Thanks for the suggestion.

[Edward J.]