Over heating query

[ronsrecord]

Wondering if any could point me in the right direction here?

Finally got the van running brilliantly after changing all suspension and bushes, and more importantly replacing all the fuel lines in the engine bay (one of which was peeing petrol over the engine - change those fuel lines people!)

For ages and ages I've had an issue with the coolant light flashing continually - but no overheating, no coolant loss, no oil loss or contamination. So I presume that's electrical.

For the past couple of days the needle has gone above the red light indicating actual overheating. But the radiator fan hasn't kick in?! Fan has been fine in the past when stuck in traffic jams on the motorway!

I've farted about with all the electrical stuff - cleaning earths, connections and testing relay 42. When relay 42 was removed no flashing light. When put back in, I had no flashing light on the first test, but the needle still indicated overheating (but no flashing light or radiator fan kicking in??!!). Second test after it'd cooled down - flashing light again. So I do have some electrical problem - bad earthing or knackered relay.

I'm starting to wonder if it could be the oil cooler or water pump - although water circulation seems to be fine??? Aaaaaargh!!

Any ideas - anything I'm missing??

[dbz864]

when you say the needle has gone above the red light? At what postion is the needle on the gauge 1/2 way 3/4 or 2/3?

[AngeloEvs]

Causes and test regards coolant warning led detailed in the WIKI.

The temperature guage coolant led is triggered by two conditions:-

1. Low coolant in the header tank via module 42 or 43 (either may be fitted)

2. High coolant temperature that causes the sender resistance to fall to 50 ohms or thereabouts.

Since the flashing stops wth the module 42 removed suggests a problem with that part of the circuit. Check for poor connections at the level sender, the level sender itself, or at the crown spade cluster located close to the fuse box.. Another common problem is a poor connection of the middle nut (the smaller one) that secures the guage to the pcb membrane. This middle nut provides the earth connection for the temp guage internal circuit and any intermittent connection here will trigger the led flashing sequence.

[boatbuilder]

Or if your engine is actually overheating, your thermostat could be faulty or radiator clogged up/needing replaced

Sent from my SM-G920F using Tapatalk

[ronsrecord]

Thanks for your replies. Yes - the middle nut behind on the pcb is loose - it had fallen out. But there seems to be nothing to secure it to?

Gauge rises about 2/3rds.

[AngeloEvs]

The temperature guage has three threaded studs the middle one is smaller diameter and requires a smaller nut. The middle stud provides the earth path for the temperature guage internal microchip and must have a good secure connection to the membrane pcb. This connection does not affect the normal function of the guage, only the led requires it.

[ronsrecord]

Thanks Angelo - had a look - centre stud solid. Checked the radiator fan switch and it only works on one side not both.

Just ran it again - the temp needle sits on top of the red light - but goes no higher. Ran it standing for ages - no radiator fan coming on though.

[AngeloEvs]

The temp guage internal LED circuit activates when the coolant sender resistance falls and the LED flashes. Once coolant temp returns to normal it stops flashing. However, the low coolant warning is via the module 42 or 43 and once triggered (due to low coolant) can only be re-set by switching the ignition off. Any high resistance in the coolant level circuit will trigger module 42, hence the problem with poor connections.

From your description, the LED stopped flashing when you removed module 42. I would check the coolant level and remove the module and run the van for a few miles to operating temperature. If the LED starts flashing at any point (other than when you switch the ignition on) then the fault is either high coolant temp, faulty temp sender, faulty wiring, faulty supply/earth to the gauge or temp gauge itself.

If, with module 42 removed, it does not flash then the fault is in the coolant level circuit. Of course, there is murphys law and it may be a combination of causes. When checking the coolant level in the header tank (engine cold) I have the engine running, increase rpm by hand then remove the dalek cap in case there is an air lock and the level drops when engine is running.

[ronsrecord]

Great - thanks Angelo, I'll give this a try and report back.

[ronsrecord]

Today's test. Took out module 42 (it's actually module 43), started engine and drove - led continuous flashing from start up. So I guess I need to look at faulty temp sender, faulty wiring, faulty supply/earth to the gauge or temp gauge itself.

[AngeloEvs]

If the temperature guage is not swinging hard right then I would eliminate the temp sender and wiring to it. My first tests and inspection would be the gauge and the pcb membrane, particularly the earth path from the middle nut to the edge connector.

The micro chip in the gauge is triggered when a voltage is applied at switch on. Any intermittent or poor connections both on the supply side and the earth side mimic ignition switch on. Check the regulator is mounted firmly and the condition of the edge connector both male and female.

[toolsntat]

Not got the watercooled on the road yet and really hope I don't have this sort of unfortunate problem when I do Ron.
Some fantastically detailed information here, well done.
Hope you're sorted sooner than later
Cheers
Andy

[ronsrecord]

Thanks Angelo - will have a good look and sort out this weekend. Need to take the dash right out to put in a new heater fan anyway. Your diagnostics on this have been amazingly detailed (thank you, thank you), and should be added to the wiki. Quite invaluable!



Hi Andy - just one of the many interesting journeys of Brick ownership!!!

[ronsrecord]

Aha!

Just been looking through Brickwerks site for stuff I might need and I've just spotted and been able to identify something!

Earlier I was going on about a middle nut being loose on the pcb.... I now see what this is...... it's the screw for the voltage regulator which holds it to the dash (and possibly earths it?). Could this be the/one of the problems? (fuel gauge works fine though)

[AngeloEvs]

Any poor connection with respect to earth, supply (including regulator) will trigger the temp gauge internal micro chip. Once triggered the LED flashes for a period of seconds. The needle movement is not necessarily affected by the intermittent fault. The Regulator must be firmly mounted and secured to provide the necessary heat dissipation and an earth path for the regulator to provide a stable 10v output.

A poorly mounted regulator will definitely trigger the temp gauge micro chip, the condition of the regulator legs should be inspected, remove the screw and remove the regulator from the socket.