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#15
by
ORCoaster
on 09 Nov, 2025 19:31
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It is easy to put on an aftermarket temp gauge. Some take a sender that screws right into a place on the flanges in place of the coolant temp sender. Generally you need 12 volts off the ignition, a ground and lights tapped into your instrument lights. There are others that are mechanical and again screw into the coolant flange and route a spring coated wire to the gauge in the interior. I like mechanical ones but the newer electric ones are easier to install.
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#16
by
fatmobile
on 10 Nov, 2025 08:08
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There is a way to unscrew the speedometer from the cluster.
I call it "the snake arm posture".
I sit on the ground with my back to the rocker panel.
Then slither/reach up behind the dash with my right hand.
Left of the steering column.
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#17
by
dbird
on 10 Nov, 2025 09:43
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Here is an image of my fuse panel. I tried some of the fuses that I believe the temp gauge/fuel gauge would be hooked up to, they look good. There is some weird stuff going on around it though, not really sure.
Here is a picture of the inside of the dash (where the radio would be): There's a white wire with blue stripes that is completely disconnected.
This is looking inside from the radio hole, pretty much looking forward towards the front.
And here is another picture of a wire that is disconnected. This is looking down from the hole where the radio would be, looking towards the passenger side of the car.
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#18
by
fatmobile
on 10 Nov, 2025 17:11
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The brown wires are ground wires unless previous owner added them.
Like the bottom pic where a blue wire is twisted to the brown wire bundle.
I can't think right off what the green/yellow wire in the first pic is for.
Looks like the previous owner liked to strip the wires and use the twist connectors.
So the stripped wires might go to the twist connector nearby.
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#19
by
ORCoaster
on 10 Nov, 2025 18:22
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Speedo cable is easy to get to in an MK1. I always get the defroster / vent pipe out of the way and lay in the foot well and look up. Might take the front seat out if you are not skinny as a squirrel.
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#20
by
dbird
on 14 Nov, 2025 07:03
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I pulled the instrument panel and tested both the temperature sensor and the fuel gauge with a 9v DC battery. I put wire on the positive end of the battery and put it against the positive nut behind the sensors and just placed negative on negative. The temp gauge made its way all the way to hot and stayed there, and the fuel gauge went to full and stayed. I replaced the voltage regulator, which the ones I have are a little different, so I had to bend the pins a little to make it work, but it fit in there eventually.
I plugged the instrument panel back in, switched the key on and saw all of the lights turn on, including the glow plug light which turned off once the glow plugs got hot. I saw the fuel gauge go up to about 3/4 full, sounds about right. I switched the key off and began to reinstall the cluster, but after I put in the 2nd bolt, I decided to switch the key on again, and I saw that the lights didn't work and the fuel gauge was empty. I messed with the main power that goes to the cluster, and I noticed that pushing on it made them go on again. I want to note that I have the cluster that has the main power connector on the top, in the middle. Anyway, I messed around with it a bit and gave it a little shake before I put it in, and everything still works on now.
I started it up and ran the engine for a good 30 minutes, and the temperature gauge goes up, the needle seems to stop around the middle of the gauge, around the same time the rad fan kicks on.
Anyway, I appreciate your guys' help, I'll consider this resolved, for now. I still haven't assembled everything yet, so if you guys have any recommendations on how to permanently keep that main connector from disconnecting or whatever, I can definitely try it out. Thanks!
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#21
by
ORCoaster
on 14 Nov, 2025 18:32
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I thought the big plastic plug sort of clipped in. I have mine removed totally as I run a Dakota Digital dash in that cluster spot. The plug is just pushed up in the back of the dash so it is out of the way. If I ever need to pull that cluster for servicing, which I almost had to do today I can swap in the old cluster with the tach in it and not have to park the pickup.
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#22
by
fatmobile
on 15 Nov, 2025 21:09
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Maybe the contacts for that connector should be cleaned.
It does click/snap in right?
The clips are all working?
And maybe some deoxit.
The radiator fan doesn't come on when the needle is straight up.
Supposed to come on closer or into the red on the gauge.
A candy thermometer in the coolant reservoir can give you some idea of how hot it is,...
if your gauge is close.
When the fan comes on.
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#23
by
GypsyR
on 13 Apr, 2026 17:22
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Rambling through older posts I found this one and discovered in it that the unused two wire sensor on my engine might be an A/C shutoff sensor. How the heck I've never noticed that in the Bentley diagrams I don't know, but I'm pretty sure I'm going to rewire my compressor a bit to use it. Because...now that I know it will bug me.
Also just noticed though I registered here 20 years ago I'm still a "newbie".
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#24
by
ORCoaster
on 14 Apr, 2026 18:33
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Yes, with only 18 posts, your time on the board means little to nada. Get some conversations going, and your status will change.
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#25
by
fatmobile
on 15 Apr, 2026 18:46
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Right, the big thermoswitch in the front radiator waterneck is inline with the power to the AC.
Shuts it off if the coolant temp is too high.
Glad to hear you still have a VW diesel to work on.