temp gauge false reading?

[kingdalg]

hi, ive been slowly going through 'running to warm' problem for a week now and im at my wits end. my 82' devon 1.6 diesel has always run a at 2/3 on temp gauge since i had it. the story so far -

failed sniff test at work so replaced head with recon, new expansion tank, genuine VW dalek, head set and head bolts

bled coolant system several times - radiator only hot at top half and stone cold at bottom

suspected thermostat - replaced with new (tested new one to make sure)

inspected water pump- ok

after much head scratching found out radiator feed pipes wrong way round - refitted

radiator still faulty - removed and flushed with hose

still the same!!! ran coolant with flush added and no stat in - result! radiator hot all over, great flow through matrix great running temp through out system!

but the temp gauge still reads around 2/3 mark!!!

tested sender - 120 ohms at cold, fitted spare sender, still the same!

ive just been out to van to clean pcb contacts and now the temp rises to 1/2 with ignition on and engine stone cold?
i disconnected sender and still problems there??

any body got a clue? my van doesnt have 43 module, its the old type fuse board. please chucked my a life line before i hang myself or set fire to the van!!!

[AngeloEvs]

The senders resistance seems low at 120 ohms for a cold engine but you say you have changed the sender - have you measured the old one and the new one at boiling point in a pan of water?

According to the VW schematic for 1982 Diesel, the temp guage connection is pin connector 6 (Blue/Yellow) on the edge connector to the dashboard. The wires in the edge connector can be accessed by simply prising one half of the connector housing away. You can then remove the Blue/yellow wire from the connector housing - snap it back to-gether and refit the connector to the back of the Dashpod minus the Blue/yellow wire. The colour code is from the VAG manual but it may be different - its conX 6 whatever the colour code.

With the ignition on, the temp gauge should not move (there is nothing connected to it!). If it starts to climb then the fault is with the gauge or the PCB membrane circuit. I notice that the Diesel Temp Gauge includes a coolant over temp led but not a module 43 so it could be possible for the internal circuit that triggers the LED to be at fault.

If the gauge does not move then the fault is to do with the wiring to the temp sender in the thermostat housing.

[kingdalg]

thanks for reply, i sussed the temp gauge moving to 1/2 point today. the temp sender wire is piggy backed to the water level sensor and the contacts were very corroded. i cleaned them up and the temp gauge just nudged up to the very first white marker on gauge with ignition on. is the needle suposed to move at all with ignition on? cheers

[AngeloEvs]

If it nudges slightly I would generally consider that Ok. Not quite sure what you mean when you say the wiring is 'piggybacked' to the coolant level sensor.

I will look at the VAG schematic again but I didn't see any connection from the temp gauge other than to the temp sender which is odd given there doesn't appear to be a coolant level module shown in the 1982 Diesel wiring diagram but you have a coolant level sensor fitted and a temp gauge with a coolant LED.....that is very strange....


E D I T:

just looked at the 1982 Vanagon Diesel Wiring diagram and it doesn't show a coolant level sender as being present - only a temperature sender. My gut feeling is that since you have a coolant level sensor (two prongs that sit in the coolant tank) you should have a module 43 as well. I am thinking this digram is incorrect but maybe someone who has a 82 Diesel model can shed some light as to wether their van has a coolant level sensor. If your temp sender wire is also connected to the water level sensor (and this sensor is the same two pronged type fitted to all WC vans) then my bet is that it is wired incorrectly and does not make any sense. The coolant level sensor is designed to work with module 43 - unless VW used some other method/circuit that isn't documented anywhere.

[kingdalg]

Appriciate your post m8. my vans on funny year. take the rad, 82 - 92 models will cost around the £100 mark. mine is made in brass and will cost me £680 new! the van cost me that! i think its a rad fault now. i put the stat back in and it still runs slightly warm. i can run van at 2000 rpm stationary and get rad lovley and hot all over but take it up road and the rad goes stone cold and temps warmer than should be. not drastically but its getting on my nerves a bit. any suggestions? cheers