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Discussion Starter · #1 ·
Hi all,

I need some input from the Dodge electric gurus (or guri) here. I now have another issue with my ’74 W100. The gauges (fuel, oil & temp) are intermittently not working. Also the turn sigs are not working. The t/sig cam and wiring were just recently replaced and did work and do work when the gauges do come on. Fuses are all good truck runs fine.
Can someone give me a direction in which to start looking?

Thanks,
L
 

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440 and a 4 speed
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If all the guages stop working at the same time - 1st thing I'd check is the guage voltage regulator that is on the back of the instument cluster.

It supposed to bring the 12 volt down to 5ish volts and regulate the guages from there. It's basically a strip of metal that heats up and looses contact and then reconnects - the engineers figured the size metal needed to "pulse" 5 volts from the 12.

I know there is a 5-10 dollar fix using parts from Radio Shack, but I don't have that handy...I'll look for it.

But i'd look there or the connection to the guage cluster... 1st
 

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Mopar Madness - Get it...
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When you say the turnsignals aren't working when the gauges aren't working... Does that mean the turnsignals physically aren't working, or does that mean the indicators on dash just aren't lighting up (Blinking)?
If that's the case, it sounds like like you're not getting 12 volts (Or only intermittently anyway) to the printed circuit board for the instrument cluster.
I've rebuilt a few of these and I've noticed that the pins on the back of the PCB can get very loose. Sometimes ready to fall out. (These are the pins that round plug fits on) .. these pins are just a swedge-fit to the PCB.
If you find that's the problem, they can be fixed (Made better actually)
Every one of these I've rebuilt, I've automatically soldered the pins to the copper traces on the PCB. Care must be taken when you do this as you need a soldering gun (Weller 100 watt) to get the pin hot enough for the solder to stick, but if you heat the trace up too much, it may lift off the board and burn.
Each turnsignal bulb as well as the 12 volt feed for the gauges and the instrument lights/high beam, each have their own pin for voltage, but the voltage of course ultimately comes from the same place. You may have to look at connections beyond the dash itself. Also check and clean the plug that connects to the back of the PCB.

Good luck, intermittent electrical probs can be a nightmare...
 

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Discussion Starter · #5 ·
When you say the turnsignals aren't working when the gauges aren't working... Does that mean the turnsignals physically aren't working, or does that mean the indicators on dash just aren't lighting up (Blinking)?
If that's the case, it sounds like like you're not getting 12 volts (Or only intermittently anyway) to the printed circuit board for the instrument cluster.
I've rebuilt a few of these and I've noticed that the pins on the back of the PCB can get very loose. Sometimes ready to fall out. (These are the pins that round plug fits on) .. these pins are just a swedge-fit to the PCB.
If you find that's the problem, they can be fixed (Made better actually)
Every one of these I've rebuilt, I've automatically soldered the pins to the copper traces on the PCB. Care must be taken when you do this as you need a soldering gun (Weller 100 watt) to get the pin hot enough for the solder to stick, but if you heat the trace up too much, it may lift off the board and burn.
Each turnsignal bulb as well as the 12 volt feed for the gauges and the instrument lights/high beam, each have their own pin for voltage, but the voltage of course ultimately comes from the same place. You may have to look at connections beyond the dash itself. Also check and clean the plug that connects to the back of the PCB.

Good luck, intermittent electrical probs can be a nightmare...
When this happens neither work when this problem occurs, no t/sigs or indicators and the 3 guages are dead. But only intermittently. Would the guage voltage regulator totally fail or can it be intermittent?

I have another instrument panel already that I am going to go through as discussed but I'll need some time to get er done.

Herd, In another post you mentioned a relay box or power box you were thinking of using. I probably need to do the whole ampmeter wiring fix and I really like that idea. I may be heading to the Phx JYs tomorrow. Do you have any idea what vehicle might be a good donor for a power center? How may relay spaces are needed in total to sufficiently convert to a rely based system?

Thanks,
L
 

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440 and a 4 speed
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When this happens neither work when this problem occurs, no t/sigs or indicators and the 3 guages are dead. But only intermittently. Would the guage voltage regulator totally fail or can it be intermittent?


Based on this info, and my own personal experience....I would suspect a bad connection in the fusebox. My fusebox had one of the switched power wires that fed a bank of the fuses have a bad connection - I cleaned up the connection and solved the problem.

If you look at the back side of the fuse block, you'll see the main wires coming in (I think I had 3 - 1 live all the time and the other two were switched - it might have only been one). The switched wire had corroded and a simple cut / clean / solder it worked. Since all the circuits go out at the same time - I suspect this might be your problem, look at the fuse block and see if all those accessories are supplied from one power lead and trace that wire back...obviously starting at the fusebox connection.
 

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the pins on the back of the PCB can get very loose
I had this happen to the a pin on mine when I was doing the upgrade--the pin for the highbeam indicator was hanging on by a thread. I soldered it back on and all's well. Bherder's right, though, it is a bit tricky--you also have to make sure the pin is perfectly vertical so the plug slides on.
 

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Mopar Madness - Get it...
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When this happens neither work when this problem occurs, no t/sigs or indicators and the 3 guages are dead. But only intermittently.
It's probably not with the instrument PCB itself... In fact, I'd almost gaurentee it's not... You're loosing power going to 'things' somewhere upstream...


Would the guage voltage regulator totally fail or can it be intermittent?.
I've never had one 'fail' on me completely, nor have I ever had one work intermittently. Generally speaking, electrical stuff either works or it doesn't. GENERALLY SPEAKING.
Intermittent probs are 99 times out of 100, because of a bad/crappy connection somewhere.

I have another instrument panel already that I am going to go through as discussed but I'll need some time to get er done.
Unless you get lucky and take apart/replug something and it happens to correct itself, I doubt this will do any good. If it were me, since the power is coming from the other side of the firewall, I'd be looking at bulkhead connections. ALSO as stated, fuse connections also!
You might want to:
A: Take the bulkhead connectors apart, cleaning the shit out of them, a blob of die-electric silicone on each connection, and reconnecting.
B: Have someone sitting in the cab watching, while your jiggling one wire at a time... See what happens.

Herd, In another post you mentioned a relay box or power box you were thinking of using. I probably need to do the whole ampmeter wiring fix and I really like that idea. I may be heading to the Phx JYs tomorrow. Do you have any idea what vehicle might be a good donor for a power center? How may relay spaces are needed in total to sufficiently convert to a rely based system?.

I've looked at the ones in Caravans, just because I was happening to look in Caravans. I have NO idea if they, or anyone elses, is better/worse. But it would fit under the hood of our rigs pretty easy. Being as Caravans have a whole lot more goodies on them, that would/should/could need 'relayed' over our own rigs, there was ample room for fuses and relays, were one to adapt one of these to our ol' girls... ;)
 

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also check the ceramic piece with the resistor on the light switch..if it is cracked it can make for intermittant lights, but i agree with the others..if the guages are going dead..not just dead lights.. then it is the common power supply or ground.
 

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Discussion Starter · #10 ·
Unless you get lucky and take apart/replug something and it happens to correct itself, I doubt this will do any good. If it were me, since the power is coming from the other side of the firewall, I'd be looking at bulkhead connections. ALSO as stated, fuse connections also!
You might want to:
A: Take the bulkhead connectors apart, cleaning the shit out of them, a blob of die-electric silicone on each connection, and reconnecting.
B: Have someone sitting in the cab watching, while your jiggling one wire at a time... See what happens.

Well I sorta got lucky this AM. When I pulled on the steering wheel the guages came to life. Then died again a couple minutes later. Looks like I'm gonna have to replace the steering shaft sooner than I had wanted.


I've looked at the ones in Caravans, just because I was happening to look in Caravans. I have NO idea if they, or anyone elses, is better/worse. But it would fit under the hood of our rigs pretty easy. Being as Caravans have a whole lot more goodies on them, that would/should/could need 'relayed' over our own rigs, there was ample room for fuses and relays, were one to adapt one of these to our ol' girls... ;)
I checked out the Caravan part of this site and found a diagram of the PDC for a 2000 (attached). Looks like it has plenty of relay slots. I'm gonna grab one next jy trip.

Thanks,
L
 

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Discussion Starter · #11 ·
also check the ceramic piece with the resistor on the light switch..if it is cracked it can make for intermittant lights, but i agree with the others..if the guages are going dead..not just dead lights.. then it is the common power supply or ground.
The switch was changed out last year, but I will check it since it probably Made in ???.

Thanks,
L
 

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Mopar Madness - Get it...
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Well I sorta got lucky this AM. When I pulled on the steering wheel the guages came to life. Then died again a couple minutes later. Looks like I'm gonna have to replace the steering shaft sooner than I had wanted.

AH-HA!! Now that's something!
The power going to the insturment cluster is fed through the ignition switch.
There is a connector for the ignition switch, to the rest of the harness about mid-way down the steering column (In the cab) .... Being as you tugged around on the steering wheel a bit and things 'worked' and then died, I'd be looking at that connector. It may just be a matter of cleaning up that connection/connector, making sure the contacts are tight and plugging it all back together.... If you happened to find a burnt contact, it should be pretty obvious and you'll know what needs fixed.
 
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