The black sensor is the one for the temp gauge. I would start with checking the wiring with an ohm meter. This sensor/gauge work of of resistance.
I recently bought a Golf Mk2 with a G60 engine in it and I have a few small problems among which this strange one with the temp gauge.
The temperature gauge will never go more than 1/4 of the temperature scale.
First I thought it is my gauge in the cluster and I replaced the whole cluster with a Figifiz cluster.
On the new cluster the same, the temp will go at max 25% of the scale.
Then I replaced the sensors, both the black and blue one ... same thing.
I took 2 other sensors from another engine .. still the same issue.
Isn't the black sensor the one that sends the temp reading to the cluster ?
So with 2 sets of sensors changed, two different clusters (one analog and one digital) and the damn temp gauge still not working properly what else could be wrong ?
Can be a relay ?
Can be a bad earth somewhere ?
Any other known issues ?
Thank you in advance.
mine does the same thing. i dare you too drain your coolant then run it and see what happens
PS, that was a joke. Don't do that.
But yeah, its fine. the temp goes higher in my car when i sit in traffic for a while, but yeah, its normal.
1990 Jetta coupe. G60 swap.