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Old 12-31-2012, 03:24 PM   #1
daniel_salzman
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Default 1974 Scout Gauges not working

Having some electrical issues with my Scout II. I recently did a repaint of my dash and also replaced the headlight switch. When I put it back together my gas gauge, oil gauge and temperature gauge are all dead. Speedometer works fine, turn signals work fine. The alternator gauge works fine but is directly wired and I didn't disconnect that when I pulled the dash.

I did the following...

Replaced all the fuses in the fuse box.

Checked all the plugs into the fuse box to be sure nothing came loose.

Visually checked to the connections into the firewall.

Traced the wire to make sure nothing is broken.

Very strange that the gauges worked and then suddenly didn't when I reconnected them.

Any ideas?
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Old 12-31-2012, 05:27 PM   #2
FDChappie
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Default Re: 1974 Scout Gauges not working

The gauges are run by a 5vdc power supply located on the back of the fuel/temp gauge. Check that you have 12v into that and with a test light it will be flashing as it's a pretty low tec supply.
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Old 12-31-2012, 07:41 PM   #3
daniel_salzman
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Default Re: 1974 Scout Gauges not working

The gauges are fuel and alternator immediately to the left of the speedometer and...and temperature and oil pressure all the way to the left.

I am assuming you mean the wiring that goes to the alternator and fuel gauge on the alternator side...is that correct?. The alternator gauge is working just fine. Or is the powersupply part of the plastic plug that goes into the fuel side. Apologies...I am not an electrical genius. I actually thought it might just be a ground.
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Old 12-31-2012, 10:45 PM   #4
Greg R
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Default Re: 1974 Scout Gauges not working

You might have bumped something like this loose:
http://www.google.com/imgres?imgurl=...qewbw&dur=1569

Those circuit board traces can be pretty finicky.
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Old 12-31-2012, 10:46 PM   #5
Scoutboy74
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Default Re: 1974 Scout Gauges not working

As you said, the ammeter gauge has a direct battery feed. That's why its still working. The other gauges all receive power from the fuse block when the ignition switch is in the on or acc positions through circuit 28. This wire runs to the plastic gang plug and becomes 28a which is connected to the multi-pin on the back of the oil/temp printed circuit board (pcb). From there it runs through a small, rectangular device screwed to the back of that pcb called a constant voltage regulator (cvr). This device regulates the 12 volts into an average of 5 volts which will display as a pulsing light when probed with an incandescent test light. From there it passes back through the gang plug as 28b which daisy chains over to the gang plug on the back of the alt/fuel pcb. One must be very careful when disconnecting those plastic gang connectors as the pins are very delicate and easily loosened/dislodged from the pcb. The other common issue with these gauges is the stamped steel nuts that secure the individual gauges to the pcb's work loose and the ground is lost. Best fix is to replace them with brass nuts, but at the least you need to make sure the steel nuts are snug. Now you have the current path for the instruments, so you should be able to trace it out with your test probe.
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Old 01-01-2013, 01:59 PM   #6
daniel_salzman
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Default Re: 1974 Scout Gauges not working

Ok..pulled the gauge. The circuit board connection between the post that receives the alternator connection and the post on the plug was lifted and broken. Soldered a wire between the two posts and still no luck. Gauges still dead. Thinking I will just order a new circuit board and replace that. The posts for the plug are all loose so I think I might have just broken one of those connections.

Good idea to replace the circuit board?
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Old 01-01-2013, 07:52 PM   #7
Scoutboy74
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Default Re: 1974 Scout Gauges not working

Sounds like a copper strip experienced a current overload and shorted in half. I've done it myself, by mishandling the alt/fuel gauge pod with the battery still hooked up. One quick touch of the wrong spot(s) to metal and presto zappo...bye-bye copper strip. If you have a test light, it would be easy for you to trace the current path in the manner I described to determine where the failure point is. Apparently it is upstream from the break in the copper strip. If you could post a good pic of the pcb sans plastic gang plug I might be able to tell you if its salvageable or not.
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Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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Old 01-06-2013, 04:55 PM   #8
daniel_salzman
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Default Re: 1974 Scout Gauges not working

The copper was really badly damaged. I went ahead and got a new circuit board and installed it. The lights in the gauges work now but the fuel is buried over full and the temperature gauge is wandering around mostly in the hot area. Oil pressure is not registering. Read some of the other forums and they suggest my cvr might be bad. I am going to pull that and see what I can do with it. If I have to replace that where would I get one?

Also, can I leave the gauges connected or will they fry without the cvr?
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Old 01-06-2013, 05:14 PM   #9
daniel_salzman
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Default Re: 1974 Scout Gauges not working

Two other things...

There is a very small chance that I reversed the wires on the alternator gauge when I reinstalled it. Can't imagine I did this but it is possible. The gauge is working fine...could that be the problem?

Also, can I run the car if the cvr is fried? Will I fry the other gauges. I was careful to turn disconnect the battery quickly when I saw the fuel gauge buried. I have to drive the car tomorrow so am wondering if I reconnect the battery will I kill the gauges?
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Old 01-06-2013, 06:39 PM   #10
Greg R
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Default Re: 1974 Scout Gauges not working

Protect the gauges!

If there is any chance the gauges are getting over 5 volts for long periods, or they are buried to the right as you say, yes they will fry as they are the "toaster wire" type.

Are you sure the voltage is correct? Maybe a ground issue?

If it is a cvr, I've found one of these is a good replacement and fits the bill better than the electronic ones:http://www.google.com/imgres?imgurl=...q9qewbg&dur=59

As far as sourcing one, I've had good luck with carquest. I'm sure a good parts jobber can do the same and the cvr is common to a lot of 60's and early 70's chrysler.
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Old 01-06-2013, 06:52 PM   #11
Scoutboy74
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Default Re: 1974 Scout Gauges not working

The gauges need the cvr. Full voltage will ruin them. For now I'd carefully disconnect the plastic gang plugs from the back of the gauge pods until you have more time to trace the issue. No chance of damaging them any further that way. They just won't register.
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Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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Old 01-06-2013, 07:13 PM   #12
daniel_salzman
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Default Re: 1974 Scout Gauges not working

One other question. I've read through a lot of the threads on the topic and everyone says the cvr is on the temp/oil gauge. There is one there but there is also one on the gas gauge. Which one should I replace?
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Old 01-06-2013, 07:35 PM   #13
Scoutboy74
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Default Re: 1974 Scout Gauges not working

There should not be one on the back of the alt/fuel gauge. This could be part of the problem. Only one is necessary. Only one should be there.
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Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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Old 01-06-2013, 08:41 PM   #14
daniel_salzman
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Default Re: 1974 Scout Gauges not working

Strange, it was there when I bought the car. The gauges were working although the fuel gauge never moved above half a tank. There is also a place in the circuit board for the cvr on the fuel gauge...I actually re-installed the cvr when I got the new circuit board. I will send a picture when I take it back apart to replace the cvr on the oil/temp side.
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Old 01-06-2013, 10:25 PM   #15
Scoutboy74
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Default Re: 1974 Scout Gauges not working

The pcb's are slightly different between each gauge pod, though they have the same shape and can be attached to either pod. One is specific to the oil/temp pod with the provision for the cvr and one is specific to the alt/fuel pod with no provision for the cvr. Now it might be that someone along the line pulled a dumb butt switcheroo on the pcb for your alt/fuel pod and installed in its place an oil/temp pcb. The pics should easily confirm or deny this theory.
__________________
Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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