Water/Coolant Temperature Gauge (barely registering!)

[adstar22]

Newbie owner, just bought a loverly 1985 1.9 water cooled pickup.

I have a few "issues" which I need to work through before I put "Bob" to work moving house and emptying gardens and garages!

Issue 2 - Temperature gauge

Drove the little beasty 50+ miles home on saturday, through a heat wave. Addmittedly I wasnt sat in traffic. But I would expect the gauge to set somewhere near "upright". However, rather worryingly, my gauge didn't get out of the "stone cold white section" on the left of the gauge. I'm currently not worried, as te system appears to be under pressure and full of water. I lossened the expansion take cap on a cold engine, and water started to come out (should I be concerned?), and the reserviour is also up to the max.

As an aside, it would appear that the other "lights" appear to be working correctly. I am aware that the dash display can sometimes be effected in general. But if I need to check somethign specific I am more than willingto look!

So, armed with a haynes manual I have a very vague idea of where to look. But the book isn't actually that obvious/helpful in this area. Could people advise me of the following:

1) Where is/are the temperature senders whcih effect the gauge. I have an idea... but the more I read the less sure I am! So a definative answer would be appreciated

2) is it possible to check the unit without takign it out of the cooling system (which would then force meto refill and bleed the system... something I'd like to avoid)!

3) Anything else I could look at to get this vital gauge working again!

Thanks in advance - more questions to follow!

[Fritz]

Just a couple of things to check before you get stuck into checking/swapping electrical components.....

During your journey was the heater blowing very warm air into the cab when all the levers were placed into the corresponding position ?

Next question did the temperature change when the levers were pushed towards the cold position ?

If you are unable to Answer the above questions, try checking to see if the Thermostat is present in the housing on the engine,,,,,if it is take it out and do a bench test with the stat in a container and check what happens when boiling water is poured over it....

Also make sure if the stat is present that the valve is NOT stuck in the open position....

Once you have checked the above then come back for further instruction...


Regards


Fritz,,,,,,,

[adstar22]

Hi Fritz,

The heater was blowing very warm air into the cab pretty much where ever the levers on the heater were located! Moving them around had no effect on what the temp guage did (or didn't do as the case may be!). Now I have done a bit of reading on this, and there is a chance that the heater cables have been effected by the addition of a stereo into the dash. So it would appear I need to check whether the heater cables are actually working. However, that would at least confirm that there is hot water in the system.

Interesting what you hinted towards with the thermostat being stuck open. However.. would it really take over an hour for the coolant to warm up and register on the temp gauge, even if the thermostat was stuck open (missing)?

Further instruction appreciated! Although I am still hoping to be able to test things without drainign the coolant system... if possible!

Thanks

Adam.

[Fritz]

Adam, belive it or not the Temp gauge may not show any signs of movement if for example the Thermostat was missing completely, ( bear in mind you will have at least 3 gallons of water to heat up during your trip, and unless you start up and hold a fast idle for quite some time the general water temperature will stay generally low unless it is restricted by a temperature controlled valve ie the Thermostat.

,,,all I am saying is check the basics before you get involved with electrical issues.......


Regards


Fritz,,,,,,,,,

PS, a Robert Bentley ( Vanagon) workshop manual is the best option when checking for potential electrical faults,,,,,I mean to say it has sections that will help you test for similar problems to what you are having.....

[adstar22]

True. I will have to set some time aside to start poking around. Other issues/symptoms - like apparently being pressurised when cold, would suggest I need to bleed the coolant system anyway.. so replacing the thermostat is a fairly cheap easy job to do at the same time.

I will keep my eyes open for the recommended book as well.

[Ian Hulley]

To check the wiring if it has the early cooling system take the single wire from the sender and touch this to earth ... the guage should go up to the top. For the late system take the plug from the temp. sender and bridge the contacts in the plug with a short piece of wire, again the guage should go to the top.

If the guage doesn't go to the top there's a wiring, connector or guage problem, if it does then there's likely to be either a sender issue (replace) OR there's a genuine cooling issue which you'll need to investigate further as a matter of urgency.

Hope this helps, Ian.

[adstar22]

One assumes I should have the ignition on to perform these tests?
But that is exactly what I was looking for in order to get a better idea of what problem I am looking at!

Thanks

[Ian Hulley]

One assumes I should have the ignition on to perform these tests?

Indeed.

Ian

[VERAT25]

hi .
as above like ian explains it:

be prepared for grief when taking off thermosat(if your unlucky like me).
all bolts snapped off clean when trying to undo. aghhhhhhhh

this was the start of saturday grief/ managed to drill out inserts and fit m8 bolts.(not easy with housing in place)
new thermo and seal now as good as the day it was born

can you not pull pipe off to check if thermo is in tact????.

verat25(cardiff)

[Ian Hulley]

Do you have the early metal housing at the rear of the van or late black plastic type at the back left as you view the engine ? The late type is still available, I believe the early styleee is only available pre-loved from one of the club's resident breakers.

Ian.

[VERAT25]

ian.............if you mean me verat25 i have the plastic type..............have sourced one from vw .de at 39 euros

metal one from france £120

verat25

[adstar22]

so far no good!

Single wire (red and yellow) rfom what appears to be an early metal type.

Tried a few different "earths".. and no movement on the gauge... will continue.. but I think I am spending next sunday overhauling the cooling system!!!

Assuming it is the wiring and not the sender.. how best to test/replace it??

Grr... I have inherited someone elses problems with this one!

[AngeloEvs]

If you shorted the red and yellow to a good earth/chassis point as Ian suggested, and the gauge did not move, then you need to start checking at the dashboard end. When doing that test always wait for about 30 seconds or so with the ignition left ON as these gauges have a damping mechanism which slows the rate of movement. Does the gauge move at all when you say it stays in the white band? You may just have poor connection at the multiconnector which connects the dash to the elctrical system and a common problem with these vans. Alternatively check that the nuts that secure the gauge to the rear of the dash and connect it to the flexible membrane circuit are fully tightened. I take it that the red LED (situated in the guage) flashes for a few seconds when you first switch on the ignition?

[adstar22]

Ok.. tried a couple of "earth" points. The engine compartment closing bracket, the coil mounting bracket. Had the ignition just on 1 click (the other dash lights on as expected, red temp light flashes then goes off as normal) and the gauge doesn't move. Tried it with the engine running.. and nothing.

Until I sort the tax out, I cant take it out for a run to see what the gauge does.

I have checked all the other switches and lights, and they appear to work on the dash.... woudl it be worth cleaning everythign behind it? how hard is it to get the "console" out so I can spray and clean everything.

Probalby need to do something similar to replace the speedo cable anyway?

I am planning on replacing the thermo stat and bleeding the cooling system next weekend. At least I was until I found the "bleed screw" in the engine bay. I will try and get pictures, but from the elbow containing the thermo switch there is a hose containing a bolt in the end sealed with a jubilee clip! Somethign isnt right in the engine bay!

[AngeloEvs]

If the gauge didn't move with the wire shorted to chassis it won't move in the future untill you isolate where the break is between the gauge and the sender. The wiring for the temperature gauge routes through a connector block housed in a Black junction box located in the engine bay. It is black with a flip up lid and placed on the rear panel in the vicinity of the coil. Inside you will find two round multi pin connectors and I would separate them and check the condition of the wiring and the male/female pins for fit, tarnishing, corrosion, etc. Same colour code so the temperature gauge pins are easily identified - best of luck!