Club 80-90 Forums

Dear all,

I have a 1990 2.1 Caravelle conversion which has just had a new engine fitted by the VW engine company. Various other bits replaced as well, including new sensors for engine temp etc. Since the new engine went in (and new accessories), the temp gauge has been reading higher than it did previously, generally sitting up on the 3/4 mark in town traffic, dropping down to just above 1/2 on a motorway run. The high temp light starts flashing just before it hits 3/4 which means it is flashing almost continuously on any non motorway drive over about 20 mins. The guys at VW engine company have run various tests, including using a manual temperature gauge to check engine temp, and the engine seems to be running at normal temperatures despite reading high and the light coming on. Coolant levels etc all fine.  Fan also working and kicking in at correct temperatures but the warning light comes on before those temperatures are reached.  They are engine experts but completely baffled as to why this is happening when the engine is not running hot.

We are assuming it must be some kind of electrical issue leading to a high reading on the dash which then triggers the light when it reaches a certain point on the dash gauge. Has anyone come across this before or have any ideas about how we can get the dash aligned better with the actual engine temps again? Should we be speaking to an autoelectrician to try and fix this issue instead? It's a bit unnerving driving with the warning light flashing and having no visual reference to know if the engine is getting a bit too hot...

Any thoughts/ideas/similar experiences very gratefully received!

Many thanks,

Rosa



 

First question would be to ask if he has fitted the correct senders or even connected them the correct way round.
ECU sender connected to gauge loom plug.
Gauge sender connected to ECU loom plug.
Assuming the later engine set-up with 2 x senders.
One for the gauge and one for the engine control unit.

You could ask about a faulty No 43 relay-like control unit in the fuse box.

Otherwise, you would be looking at something causing a partial short to ground. - unlikely.

Robsey wrote: ↑24 May 2021, 09:42 First question would be to ask if he has fitted the correct senders or even connected them the correct way round.
ECU sender connected to gauge loom plug.
Gauge sender connected to ECU loom plug.
Assuming the later engine set-up with 2 x senders.
One for the gauge and one for the engine control unit.

You could ask about a faulty No 43 relay-like control unit in the fuse box.

Otherwise, you would be looking at something causing a partial short to ground. - unlikely.

Thanks for this - yes the senders are correct and correctly fitted.  Would the faulty control unit you mention cause this specifically? As the rest of the dash indicators all functioning normally.
Thanks,
Rosa
 

Not sure if this is related and I don't have the same engine as yours, but I noticed that that my temperature gauge rises when I have the lights on, I have brought this up on the forum and was told it could be a voltage regulator in the dashboard.  Mine did not activate the overheat light but I did notice a definite rise in the temp gauge needle when lights were on and then reduced when lights were off.

Change the temp gauge sender .
you can test the temp gauge with a 100 ohm load instead of the sender , but I suspect it’s just the sender , just because it’s new doesn’t means it’s not at fault 

I picked my van up from VW Engine Company on Thursday.   Brand new turnkey, fitted by them.   Temp gauge also reading 3/4 at normal running but my light so far has only flashed on normal start-up.   The temp gauge stays put unless I have the heater on when it drops to centre position.   I also queried with VWEC about this high reading and was assured my engine is operating in normal parameters. 
 
I wonder if they have got a batch of high-reading senders? 
 
I would add my fan is coming on in normal conditions and in addition to VWEC's own assurances my new engine seems to be running at normal temperatures.   I'm going to get it checked again by my usual garage though on the 500 mile service.....

I swapped my old gauges out for a rev counter with gauges. My old one registered just above the white mark at temp where this one registers 3/4 and half with the heaters on.

My light sporadically flashes recently as well so I think I gotta go hunting for electrical gremlins. 

You could remove module 43 from the fuse box just to eliminate it as a potential cause but the best test is to remove the connector from the coolant temp sender, run the engine and take various measurements with a multimeter of the senders resistance. At normal operating temperature it should read around 100 ohms, if it’s in the region 50 to 70 ohms then the sender is either incorrect or the coolant is hotter than it should be. You can also test the sender (but unfortunately it has to be removed which means losing coolant) by suspending it in a pan of water and heat it, at near boiling point it should read somewhere close 100 ohms.

Thanks all! Will try these suggestions. Much appreciated, will post when we discover the answer

mercrocker wrote: ↑24 May 2021, 14:13 I picked my van up from VW Engine Company on Thursday.   Brand new turnkey, fitted by them.   Temp gauge also reading 3/4 at normal running but my light so far has only flashed on normal start-up.   The temp gauge stays put unless I have the heater on when it drops to centre position.   I also queried with VWEC about this high reading and was assured my engine is operating in normal parameters. 
 
I wonder if they have got a batch of high-reading senders? 
 
I would add my fan is coming on in normal conditions and in addition to VWEC's own assurances my new engine seems to be running at normal temperatures.   I'm going to get it checked again by my usual garage though on the 500 mile service.....

Yes interesting could be a batch of high reading senders... will replace it to see what difference that makes

Hey @rosar, did you get to the bottom of this is the end?  I had the same and couldn't find the issue.  Am hoping to go to VWEC for a new engine soon so would love to know the fix if you found it!