rad fan and fuel guage aint workin'

[tkisling]

I was wondering if you guys could help me. My rad fan does not turn on at all, even when the car is at operating temperature.

Also my fuel gauge isn't working even though the tank is full. Is there something in the cluster that can cause  :-this?

[mystery3]

Did they both stop working at the same time? Do you have the bently manual? There should be procedures for testing the wiring and sensors involved? Checked your fuses?

[somolovitch3]

And what year/make of vehicle is this?
Fuel gauge and temp gauge are fed ~10 volts from a small 3 pin voltage regulater on the back of the cluster.
Radiator fan has a temp sensor mounted in the radiator, try jumping those connection and see if the fan runs. It also has a fuse in the fuse panel..30 amps.

[tkisling]

Its an 81 Rabbit diesel L. The fan and fuel gauge didn't work when I bought the car. I am planning on ordering a bentley from amazon.

[tkisling]

I jumped the two prong plug to the radiator fan switch on the side of the radiator and then the fan turned on. I am planning on replacing this switch. Does this sound like the most likely fix? Also tried to take off the cluster, but couldn't get it out. My fuel gauge still isn't working, any ideas?

[Quantum TD]

As noted, the fuel and temp gauge share the same circuit. Usually, when they both stop working, it means that the voltage regulator is bad. It's located on the back of the cluster and is held in place with a small slotted screw. Then, it simply slips out of the printed circuit.

In my experience, the main reason they stop working is due to grounding issues. The ground at the fuel sending unit, is shared by the temp sender. This ground is located in the area below the rear seat (along the face), on the passenger side of the car. The only way to access it is to remove the rear seat, and peel back the carpet until the floor pan is exposed. There, you will see (covered in gorilla snot glue and carpet hair), a single phillips head screw and a terminal mounted to the vertical face of the floor pan. Undo the screw, clean up the terminal, and install a slightly larger sized screw that will cut into fresh metal and get good contact.

I've diagnosed about 1/2 dozen non-working fuel gauges. Only once was it a bad cluster (well, just a bad printed circuit, the gauges all worked fine by themselves). Never was it an issue of a bad voltage regulator. Nearly everytime the gauge didn't work, it was because of bad grounds.

If you do that and the temp gauge still doesn't work, check the wire for cracks. They tend to break from age an heat.

[tkisling]

The temp gauge is working but the fuel gauge is not. I ordered a new rad fan switch from NAPA in hopes that it will fix my fan not turning on.

Do I need to drain the cooling system to change this fan switch on the side of the rad?

[Quantum TD]

The temp gauge is working but the fuel gauge is not. I ordered a new rad fan switch from NAPA in hopes that it will fix my fan not turning on.

Do I need to drain the cooling system to change this fan switch on the side of the rad?

Nah. Just do it when it's cool, and pull the cap to release any residual pressure (which there shouldn't be if the car is stone cold). Put a pan under it and slip a wrench or socket over the switch. If you're quick enough, you won't lose too much coolant. Put a pan under it so you can catch it.

I missed that part about the temp gauge working. In that case, I'm 99% certain your ground connection is bad. The sending units rarely go bad, unless they're rusted. You can check that too while you're checking the ground. It's pretty easy to do.

[tkisling]

Thanks for the info. I am going to change the switch soon. Although I might get a different, less rusty car, for $100 more than I paid for this one. I also plan on checking that ground.

Will the fuel tank for an 84 gas rabbit work with my 81 diesel?

[Baron VonZeppelin]

The 81 Truck I'm doing had a fuel gauge that stayed on Empty.
I knew I had 4 gallons of fuel, for fact.
I couldn't live with that, so started checking stuff.

Got no current at the disconnect plug under the vehicle - near tank.

Luckily have a spare gasser cluster on hand (Thanks Wolfburged !).

The temp gauge works fine in Truck, but for sake of eliminations,
swapped regulators on back of cluster - with no change.

Put regulators back as they were before - then plugged in the gasser cluster into my Truck. The fuel gauge worked.

My actual gauge was Bad.

So try checking for voltage (test light) - with ignition switch ON - at the disconnect near the tank.

Also note, a bad ground "usually" will read FULL all the time.
Also note, you could have multi symptoms that require more than just one repair. Also note, anything is possible with a Mk1 when it comes to failures/problems. New tires can make your glowplugs burn out. Fresh paint job can kill your starter. Valve adjustment can make a rear wheel bearing fail. Etc....

Did NOT want an UNLEADED cluster in my Dzl. And would rather have a functioning clock than a non-functional tacho. I swapped gasser fuel gauge into my original Diesel cluster.
Viola' - fixed.
Gasser also had a perfect odometer drive gear. Mine was cracked/not working. The 1,064,263.5 mile odometer lives again !

Many thanks to Wolfsburged for that spare cluster.
I might use the tacho from it later too, with a Dakota scrambler.

The 84 gasser tank will "work".
But you might need to remove an in-tank elec pump, if it has one.
And possibly some small mods to hose connections.

I would try the instrument cluster from the 84 first, instead of the tank.

[Baron VonZeppelin]

...Also tried to take off the cluster, but couldn't get it out. My fuel gauge still isn't working, any ideas?

If your car has the pull-knob type headlight switch - the hardest part about removing a cluster - is getting the fascia/bezel off. You have to go in from underneath and find the spring loaded release button at the back of the headlight switch box - push the button in - then pull the knob/stem out of the box. (This also leaves you with your lights ON - so might want to disconnect battery first.)

Other than a half dozen screws, the only thing you need to get loose is the speedometer cable from the cluster. Its a round collar where cable meets cluster and it unscrews. Think you have to get at it from underside too.

The big snap-in electrical connector on top of cluster can be unplugged after the cluster is pulled out/tilted from dash far enough to access it easily. It has snap legs/ears on the connector.

You don't have to remove steering wheel. You can tilt cluster and remove it towards driver side door. Or you can remove the steering wheel.

The only thing worse than a non-working fuel gauge, is a broken odometer coupled with a defunct gauge.