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Discussion Starter · #1 ·
Are all 73-80 the same? (Except tack option) Or interchange 1:1?

All lights out on mine and fuel gauge not working. Pulled the dash. The big center missing 3 pins. All bulbs burned out and amp meter melted along With that top left housing.

Someone locally has one pulled from a 74 that looks the same. Only $100 compared to Brad’s at $400. Any interchange info is appreciated.

At the same time, truck was starting and running before I pulled the instrument panel. Now, no such luck. Didn't try to re install since so much was melted and pins broken. Would disconnecting gauges cause it not to start?
 

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1975 W100 Power Wagon Adventurer Sport 318 727 NP203 3.55
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Disconecting the ammeter will prevent power from leaving the battery. there are minor differences such as oil light vs guage and the 4wd models have a difference in the lights under the radio. I think they should all work with minor mods.
 

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Discussion Starter · #3 ·
Looks like the gauges have minor differences. The trim piece on the older ones are straight where 75-80 is curved on both ends.
 

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1975 W100 Power Wagon Adventurer Sport 318 727 NP203 3.55
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it would appear you are right i double checked and some 74s had the older dash style (or had it swapped over). My 75 has this style and i think all the ones with that style will interchange. I was told at one time that I could swap the older style over but i never had a reason to do so
 

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I have a couple of those circuit boards for the back of the cluster from a couple of 78 trucks and probably 8 or different gauges. Basically I have two clusters completely dissembled. If you find out you need a certain part lemme know.
 

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Discussion Starter · #7 ·
So am I reading correctly that it doesn’t matter which way I connect the terminals on the amp meter?

I had pulled the dash to check fuel gauge and replace several bulbs now the truck won’t start.

Found that I was missing pins on the big connector. Which is why the fuel gauge was t working. Given that it was going to read empty, tried putting back together to restart. Nothing. Had lights and buzzer but no crank. Then saw smoke coming from the cluster. Looked like from behind the oil pressure but guess would be related to amp meter. Does the ampmeter need to be functional? Or is it just a pass through for current?

I read the bypass on the link above. Doesn’t make a lot of sense but I’m am a pretty terrible electrician in automotive applications. But looks like someone attempted something similar to described as I have an alternator wire/connector terminal grounded to battery tray and run along core support and an extra wire to the relay.

Basically put everything back how I found it and now it won’t start. What next?

 

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1975 W100 Power Wagon Adventurer Sport 318 727 NP203 3.55
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best guess if you have the metal housing for he guages you bumped the ammeter and made a short. use heat shrink to help yourself there. Connect the red wire on the ammeter where it says red or it will read backwards. still function but reads wrong. make sure you have 12v at the red wire. I disagree with the bypass so i just cleaned it and soldered. I've heard of replacing the studs with copper, but it is more important to bypass the bulkhead. neither should solve the issue. Start finding where you have power and not go from there.
 

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I just removed my OEM gauges and dash , everything worked fine . Amp meter was bypassed and bolt meter added to left wing . I’ll sell or trade for parts . PM me if interested
 

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Discussion Starter · #10 ·
Amp meter was fried and partially melted cabinet. Pulled a 74 from the salvage yard and it’s working and I can start my truck again.

Chasing gas gauge now. Tested the sending unit when installed. Unsure if it’s a grounding issue at the tank or broken wire. Going to try gas gauges from both clusters to hopefully determine if it is at the gauge or further back.
 

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Those pins for the main circuit board connector are often a problem. I think some people have soldered them back on. Also recall something about using a small screw to physically attach them to the board and then maybe soldering a jumper. Just because the pin looks attached doesn't mean it's making a good connection and like that.

When (not if) the ammeter fries, the whole truck generally goes dark. One or two things still work but I forget what exactly. Connect the red and black leads together using a small bolt / nut, tape it up, ignore that gauge. Another kinda dumb thing is that they use the same circuit board for oil pressure gauge vs oil pressure idiot light. If you have the gauge and put a bulb in what looks like just another hole for a dash light (except it's between the gauge legs) you shunt the gauge and it will read a constant 40 lbs or so - even with the engine off.

The brief puff of smoke may have been the voltage limiter going poof. In that case, none of the gauges (temp, fuel, oil) will work.
 

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'79 Macho 360 Magnum, Comp 480 cam, Hughes springs, 650 Thunder AVS, Pertronix Flamethrower ignition
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The basic layout of the dash is the same from '72-'80 but it cosmetically changed in '75 and basically stayed the same up till '80. The dash pad also changed in '75 and stayed the same till '80. Bypass that amp gauge entirely. The same thing happened in mine. It also melted the plug in the main junction on the firewall. I ran a new wire through the plug on the firewall and joined the wires behind the gauge so the circuit goes back to the relay. I also ran new fuseable links. Here's an awesome diagram:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml
 

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Discussion Starter · #13 ·
Yep, puff of smoke seemed to be voltage regulator. Bought a parts cluster swapped out the cabinet that was mostly melted from a 74. All gauges (except temp) working now. Speed ometer is bouncing.  See to reseat the cable and see if fixed. If not I’ll swap out other one.
 
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