Instrument Cluster Gauges not working.... help!! (1 Viewer)

[piecemeal]

I have a 74fj40. The amp gauge works, as does the speedo, and the mileage counter. However, the oil press gauge, fuel gauge, engine temp gauge aren't working. I'm guessing a bad ground perhaps or maybe something got knocked loose back there since an old cable actuated winch was installed with the cables run through the firewall and these all worked prior to that. Does anyone know if they all share a common ground on the fire wall and where it's at exactly? Pics would be great!! Thanks a heap!!

 

[Hoots Magoon]

Did you check the fuse? They are also on the same circuit as the heater fan.

 

[piecemeal]

I will do that as soon as I get home. I haven't had any need to turn that on as it's been pretty hot here all summer. Hopefully that's it. Thanks man!!

 

[Hoots Magoon]

If you take out the instrument cluster, don't forget to disconnect the battery first. The ammeter is directly connected to the battery, and will short on the dash causing a lot of arcs and sparks. Don't ask how I know.

 

[piecemeal]

Ok. So fuse WAS popped. Put in a new 15amp, turn ignition, immediately pops again. Where should I start?

 

[piecemeal]

I just noticed it is supposed to have a 20 amp in it. If the key is in the accessory position, and the heater fan is not on, would a 15amp fuse trip with just the 3 gauges energized? My guess is no, but I'm not sure....

 

[Hoots Magoon]

I'm no superhero, but this is what I would do. Have a beer. Make sure you have a class E fire extinguisher ready. Have a beer.

1. Unplug the heater fan. Have a beer. It is the easiest thing to eliminate. It is under the bonnet on the passenger side firewall. Then see if it blows another fuse. Have a beer.
2. Disconnect the battery and pull the instrument cluster. Have a beer. Look for anything shorting out (or touching) on the cluster.
3. Re-connect the battery. Have a beer. Disconnect one instrument at a time while having another beer until you stop blowing fuses.
4. Have a beer.

 

[65swb45]

Follow each of the wires from the senders back to the harness to check for dead shorts at the firewall/ floorboard.

 

[CaliFJ]

Have a beer

I generally suggest not drinking while doing electrical work or anything related to fuel. Brakes, etc are fine. I never follow my own advice though.

I installed a Digital Dakota and its awesome! But to 65's point, look for corrosion along points from senders to gauge. Pull, clean, install, check. I have my '76 original gauge that I'm happy to part with if the root cause is a bad cluster.

 

[Franz]

I'm with Hoots on this.

 

[DougAustinTx]

Gauges probably pull less than 1 amp total. Since it blows even in the Accessory position, I would be looking at things that have been added by previous owners including stereos......... then anything that needs the ignition to be on to work.... like the wipers etc.

 

[piecemeal]

Sounds good! Thanks for all the advice! I'll let y'all know what I find....

 

[4Cruisers]

The water temperature gauge gets its reduced voltage from the fuel gauge, so the problem could be with the fuel gauge itself. See Post #11 here: Fuel and Temp Guages, Not the same old symptoms....

This thread Fuel and Temp Gauges has even more details, and maybe should be added to the FAQs (I didn't see it there)?

One of the tiny wires on the back of my fuel gauge had shorted against another wire/component and had some black discoloration. I carefully separated the wire from where it had shorted and both gauges started working again. Just in case, I bought a good used spare fuel gauge from Classic Cruisers.

 

[piecemeal]

Thanks for the tip and link. I'll keep it in mind....

 

[piecemeal]

Well, I got lucky. There were 3 wires to choose from to connect to my brake fluid sensors. The PO had two power wires in the vicinity of said sensor. Apparently, I hooked up the wrong one that got knocked loose when I was doing a weber to THC swap and it's somehow connected to the fuse for the heater and gauges. After I hooked up the correct sensor wire and capped and tied off the PO power wire and swapped the fuse out, it's all good now. Thanks for all the advice and help.

If I may make a suggestion to anyone who has random wires under the hood that don't look like part of the "stock wiring harness", trace them back to their origin before you plug them to where you think they oughta go. If you're unsure of where said wire goes exactly, get a wiring diagram specific to your truck's year and match up the colors. It'll save you a lot of trouble and headaches going forward. Coolerman has some great wiring diagrams posted that you can find with by typing in "wiring diagrams" in the search window!!

 

[JayhawkFZJ80]

Anyone had any luck diagnosing this issue?