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Not sure where to start - electrical issues

LNimoy

New Member
Mach1 Driver - I was typing my reply and just saw this come in.
YES - headlight switch out, jamb switches out, one lead to ground and test light probe to each wire of jamb switches. Both wires hot.
L is for Leonard. Not a big Star Trek fan, haven't seen anything since the original series, but I am a fan of Leonard Nimoy. I created an email account long ago lnimoyusse@ yahoo.com, for anything that I didn't want coming into my regular mailbox. I use it for non-critical things that should never require an immediate reply. My name is John. Thanks for the suggestions.
 

Mach1 Driver

Active Member
Mach1 Driver - I was typing my reply and just saw this come in.
YES - headlight switch out, jamb switches out, one lead to ground and test light probe to each wire of jamb switches. Both wires hot.
I suggest a VOM (Volt ohm meter), not a test light, so you can see what the voltage is, then repeat the test.
 

LNimoy

New Member
Went back at it today for a while. Headlight switch out. Door jamb switches out. Both door jamb
switches tested fine using a volt meter.
Removed the wires I had installed to the firewall. Removed the radio. Removed the glove box for tracing purposes,
Car wiring is now all original wiring with no splices anywhere.
Circuit 53 = black/blue wire had 12 volts at each door jamb switch location.
Circuit 54 = green/yellow wire had 12 volts at each door jamb switch location.
Started pulling fuses one at a time. No change for the first 4 fuses.
Saved the 7.5A dome courtesy glove box etc one for last. Left all other fuses out.
So with no fuses in the fuse block, Circuit 53 = blue/black still had 12 volts at each door jamb.
Circuit 54 = green/yellow now had 4.8 volts at each door jamb and at the glove box light.
So if I am reading the wiring diagram right, that's a 50/50 at best, both Circuit 53 and 54 get power from the headlight connector through the D1(green/yellow fused) and D2 (blue/black).

Previously
I removed the switch and tested the switch harness. With the key off, I have power in the harness at the following posts.
B = black/orange wire = battery feed. This is to be expected.
D1 = green/yellow = courtesy feed thru fuse. I assume this is correct.

D2 = black/blue = courtesy lamp. This is hot with the headlight switch removed and the doors shut.

FromMach1 Driver:
Once you know that you will have to follow that circuit throughout the car to find the short. Or conversely follow the wires that connect to the lights back to the door jamb and light switches looking for a short.

Does this mean that I have to unwrap all the electrical tape from end to end on each length of wire throughout the whole dashboard
on circuits 53 and 54? Would the above info narrow down which circuit I should focus on?

Thanks
 

Midlife

Well-Known Member
Staff member
Moderator
I would first find every green/yellow wire plug within the harness and double-check that you haven't plugged in a wrong wire (e.g. at the console plugs near the engine gauge feed plug near the firewall) like for the console lights. Then, find every blue/black plug and make sure it has a mating blue/black plug in it that needs to be there (e.g. courtesy lamps, console plug, both sail (rear) courtesy lights, etc. If nothing obvious, then yes, you'll have to dig into the harness.
 

LNimoy

New Member
I would first find every green/yellow wire plug within the harness and double-check that you haven't plugged in a wrong wire (e.g. at the console plugs near the engine gauge feed plug near the firewall) like for the console lights. Then, find every blue/black plug and make sure it has a mating blue/black plug in it that needs to be there (e.g. courtesy lamps, console plug, both sail (rear) courtesy lights, etc. If nothing obvious, then yes, you'll have to dig into the harness.
Will do. No rear, console, sail panel or door courtesy lights, just under dash and glove box.
Everything is unplugged.

Would the fact that the voltage dropped from 12 to 5.5 when the fuse was removed on the green/yellow narrow down the search location?
 

Midlife

Well-Known Member
Staff member
Moderator
Well, if you pulled the 7.5 amp fuse that provides power to the green/yellow wires, you should see 0 volts. The fact that it is 5.5V may mean a stray voltage. That's why I don't like measuring voltage; I prefer resistance or continuity checks. You should see high resistance between green/yellow and black/blue wires unless the door jamb switch is operational and the door is closed or the door jamb switch is completely disconnected. I don't like testing without the door jamb switch as those lines can easily be shorted (male pins next to sheet metal). If you see 1 ohm or so resistance between these two systems, then they are tied together SOMEWHERE.

A strange question, but I have to ask it: are you underdash courtesy lights mounted? They need to be to grounded that way. Strange things happen when they are not mounted.
 

LNimoy

New Member
Well, if you pulled the 7.5 amp fuse that provides power to the green/yellow wires, you should see 0 volts. The fact that it is 5.5V may mean a stray voltage. That's why I don't like measuring voltage; I prefer resistance or continuity checks. You should see high resistance between green/yellow and black/blue wires unless the door jamb switch is operational and the door is closed or the door jamb switch is completely disconnected. I don't like testing without the door jamb switch as those lines can easily be shorted (male pins next to sheet metal). If you see 1 ohm or so resistance between these two systems, then they are tied together SOMEWHERE.

A strange question, but I have to ask it: are you underdash courtesy lights mounted? They need to be to grounded that way. Strange things happen when they are not mounted.
Thanks for the reply.
I had everything related to interior lights disconnected when I tested the voltage with the fuses removed, including the headlight switch.
I have the jamb switches out and plugs taped unless I am testing them.
Yes, there was 5.5 volts at the wire with the fuse out, 12 volts with the fuse in.
I will install the switches and test resistance tomorrow. I just crawled out from under the dash after tracing and opening up the harness.
Everything looks fine, no cracks, splices or frays. I haven't gotten to the firewall yet. I'll wait until my son comes over tomorrow to check that.
Yes, the courtesy lights are still bolted to the dash, I removed the bulbs for now while I'm testing.
I just can't figure out why these multiple problems occurred at the same time, solenoid, ignition switch, gauges and courtesy lights.
I've had the car 15 years, restored it myself, and no issues until now.
I'll check what you suggested tomorrow.
Thanks again, and best of luck this weekend with the storm.
 

Midlife

Well-Known Member
Staff member
Moderator
I'm in the Panhandle and it looks like we will be spared from the storm.
5.5 V can only be found at the output of the Constant Voltage Regulator (CVR), which makes me suspect something is wrongly attached in the dash cluster. There's no courtesy lights near the dash cluster except on the break-out of the harness at the ignition switch area which has the blue/black wire going to the right hand courtesy light bulb socket.

Can you remove the dash cluster and test again? You'll have to protect the bulb lamp pins from shorting out, as they easily slide forward through the bulb housing. The CVR wires are sometimes easy to screw up: there's a female covered spade (black/green) and a male spade (black/green), but also either a female spade (black) or male bullet (black) for ground. It is easy to switch the 2 female spades...
 

LNimoy

New Member
I'm in the Panhandle and it looks like we will be spared from the storm.
5.5 V can only be found at the output of the Constant Voltage Regulator (CVR), which makes me suspect something is wrongly attached in the dash cluster. There's no courtesy lights near the dash cluster except on the break-out of the harness at the ignition switch area which has the blue/black wire going to the right hand courtesy light bulb socket.

Can you remove the dash cluster and test again? You'll have to protect the bulb lamp pins from shorting out, as they easily slide forward through the bulb housing. The CVR wires are sometimes easy to screw up: there's a female covered spade (black/green) and a male spade (black/green), but also either a female spade (black) or male bullet (black) for ground. It is easy to switch the 2 female spades...
Thanks Midlife.
The cluster has been out since the first day. All loose plugs have been taped to prevent shorting out. Tested each one and re-taped.
I will get back at it tomorrow checking resistance.
Could the problem be with my fuse block itself? Just seems to be too many unrelated problems.
Glad to hear the storm may not affect you. I believe I read a while back that you got hit hard last time.
John
 

Midlife

Well-Known Member
Staff member
Moderator
Fuseblock is unlikely as no black/blue wires are tied to any of the fuse clips.
Did you do any work on the underdash harness during restoration?
 

LNimoy

New Member
Fuseblock is unlikely as no black/blue wires are tied to any of the fuse clips.
Did you do any work on the underdash harness during restoration?
No work on the harness at all. It seems o be as it left the factory. Clipped up in all the right places, taped nicely along each length.
I was thinking this morning, and the only thing I did during the ride that morning (see initial post), was try the cigarette lighter, and use the windshield wiper.
Neither of those have been used in at least 10 years.
I am going to remove them and check resistance on every wire that I can. Everything else is out of the dash, including glove box.
That is the only way I can get in there without removing the bench seat.
I just know that when I get it sorted out, it will all make sense.
Thanks for the responses. They get me thinking.
 

Mach1 Driver

Active Member
Went back at it today for a while. Headlight switch out. Door jamb switches out. Both door jamb
switches tested fine using a volt meter.
Removed the wires I had installed to the firewall. Removed the radio. Removed the glove box for tracing purposes,
Car wiring is now all original wiring with no splices anywhere.
Circuit 53 = black/blue wire had 12 volts at each door jamb switch location.
Circuit 54 = green/yellow wire had 12 volts at each door jamb switch location.
Started pulling fuses one at a time. No change for the first 4 fuses.
Saved the 7.5A dome courtesy glove box etc one for last. Left all other fuses out.
So with no fuses in the fuse block, Circuit 53 = blue/black still had 12 volts at each door jamb.
Circuit 54 = green/yellow now had 4.8 volts at each door jamb and at the glove box light.
So if I am reading the wiring diagram right, that's a 50/50 at best, both Circuit 53 and 54 get power from the headlight connector through the D1(green/yellow fused) and D2 (blue/black).

Previously
I removed the switch and tested the switch harness. With the key off, I have power in the harness at the following posts.
B = black/orange wire = battery feed. This is to be expected.
D1 = green/yellow = courtesy feed thru fuse. I assume this is correct.

D2 = black/blue = courtesy lamp. This is hot with the headlight switch removed and the doors shut.

FromMach1 Driver:
Once you know that you will have to follow that circuit throughout the car to find the short. Or conversely follow the wires that connect to the lights back to the door jamb and light switches looking for a short.

Does this mean that I have to unwrap all the electrical tape from end to end on each length of wire throughout the whole dashboard
on circuits 53 and 54? Would the above info narrow down which circuit I should focus on?

Thanks
I have a 69 so the wiring will be slightly different, but on mine battery power goes to fuse #6 which is 14A. That connects to wires: 54 GR/Y which goes to light switch D1, both door jamb switches, trunk switch, and the map light. It also connects to clock via 22 BL/BK, and the lighter via 40 BL/W. These wires would all be hot with the fuse in place.
What operates the lights are the three switches: light switch D1 to D2, and the two door jamb switches. They run off the 53 BK/BL wires. If any of the switches are open (off or removed) then there is no power to the lights.
You have the switches disconnected and fuses out and still have 12v on the 53 wires. This is the switched side of the circuit and shouldn't have any voltage. Then on the hot side which is 54 you have 4.8v. This is normally 12v but the fuse was out and you should have had 0v. Some voltage is back-feeding in.
Since you have 12v at the 53 wires- you have a direct short into the 53 wires somewhere. I counted somewhere around 15 plugs in the circuit. At least one has 3 wires, and if those wires are reversed it could cause some unexpected problems. I know the plug is polarized, but something screwy is happening.
I wouldn't remove the tape from the harnesses to trace wires- at least not until I had tested for voltage at the 53 wires (black with blue stripe) at every connection point (all those plugs). Follow the wire diagram to each connection and unplug them one at a time until you loose voltage. Keep following that back to the short. I know I make it sound much easier than it is.
If you still have problems then, with the fuses and switches out (and any loose wires or plugs not touching anything) test for voltage at any of the 54 wires when doing the following one at a time and record the voltage at 54: disconnect trunk light, disconnect clock, disconnect the lighter, remove the map light. Doing one of those four things should remove the 4.8v from the 54 wires.
 

LNimoy

New Member
Son stopped over and we went back at it today.
Re-checked 53 and 54 circuits to all connectors under the dash, all good. No other courtesy lights or clock.
Cluster removed, headlight switch removed. Door jamb switches installed.
My son remembered that a few years ago the main disconnect at the firewall wall separated, so we went there first.
It was firmly in place, Disconnected it and noticed on male pin looked shorter than the other. Is this normal?
Main Disconnect.jpg

Decided to unbolt the fuse block to access it better. The black wire with the spade connector was loose, as was the right hand side of the fuse connector on that same side. That fuse is for the ACCY circuit. Tightened the clip a bit and reinstalled the fuse.
Fuse Block Front.jpg

Also noticed some corrosion? on the back of the fuse block. Not sure what it is as I didn't want to pull on the wires there.
Fuse Block Back.jpg

The passenger side courtesy light now goes out when you depress the door jamb switch on the passenger side.
It does not go out while depressing the driver side switch.
The driver side courtesy light does not go out with either switch. The driver side bulb does get dimmer when you depress either door switch.

So, how hard is it to replace the underdash harness? I have everything out of the dash except the original radio.
How and where do you start unravelling all the tape in there? Is there any slack once you get started. I can barely get my hands in there just to follow a wire.

Are there replacement fuse blocks available? Do the wires need to be spliced, or can they be traced out to connection points?
Thanks again for the help.
 

Midlife

Well-Known Member
Staff member
Moderator
That short pin on the firewall is for your horns. Corrosion at the back of the fuse box seems about normal; you can throw the fuse box into a blasting cabinet to get rid of rust but you'll need some metal protectant to keep it from rusting again. Your courtesy lights are a mess and your best bet is to remove the harness and send it to me or another professional to have it gone through. It's not hard to remove: probably take you less than an hour if your dash and seats are removed. I'm still out of commission, so you'll have to wait until late this year if you want my services. My guess is that your courtesy light wiring has been spliced incorrectly between the right and left side courtesy lights...
 
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