just unplug one of them and see if the glowplugs stay on for a full 30 seconds or if they just stay on for the normal amount of time. If the engine is hot disconnect one and the temp gauge won't work.
my GP relay is screwed i think. The light doesnt make sense most of hte time so i listen to hear the relay tick in the dash but with the GP wire detatched it still ticks inside the dash so that either says i really don't know what im doing or there is an issue with the GP relay.
I detatched the GP lead from the fire wall mounted fuse to see if a direct connection to the batt with it would cause better starting, it did so i've been doing that lately.
Your suggestion makes a lot of sense but no matter what config. i have those wire leads the gauge still reads messed up readings. It never reads past the solid white no matter how i have the wires. But the needle does move to that point
its like the needle wants to go to the middle but it's stuck or something
I didn't read all the thread, but my gauge also rarely passes the middle mark (only when serious overheating took place, i mean, damage)
once I took the dash apart and studied the temp gauge.
it has three wires: ground, regulated 10v and signal input.
the sender connects here, the gauge is a simple resistor that heats when current flows, as the sender is a NTC, more heat=more current=more heat on the sender. a bimetal link gets distorted by that heat->needle moves following the metal.
there is also a circuit that drives the LED when voltage gets below 4.1V (if I remember correctly) that voltage corresponds to a given temperature in the head.
so far so good, but VW also wanted to fit the dreaded "low coolant" light :x
they put another sender in the coolant expansion tank and a circuit to interpret it (looks like a relay, #42 if I recall correctly). the output of that relay is a fast pulse, a short to ground in the same wire as the temp sender.
what it does is that the LED blinks but the gauge doesn't move because the pulse is too fast for it to react.
very nice, but now we get an old complicated system that tells us that the water is too hot, or we have no water.. when it works properly
If you wan't to check the temperature guage sender, the sender for the glow plugs is exactly the same. These senders lie all the time, I wish I knew this prior to changing that wretched arse about tit thermostat. Swap the sender plugs on the head outlet to check. If the temp guage now makes sense and the glow plug light time changes, then you know. Unfortunately hissing doesn't sound promising. :cry:
i know why the hissing is there
Its a sad tale....
Thanks for the advice!