Temp gauge

[Bonfireboy]

Hello all.
Got a T25 late last year with a few issues.
The next one I'm trying to tackle on the list is the temp gauge/flashing coolant level light. According to the person I bought it off of, he replaced the dash board but when he started it all up the temp gauge creped all the way to the right (I assume that's the hot end of the scale, not having too much experience with T25's I could be wrong) and the coolant level light flashed as well as the buzzer sounding. He had it investigated but instead of fixing it, he disconnected the buzzer and carried on. Being a new van to me, I want to make sure I know the correct temp.
So, could anyone give me a few pointers where to look for the problem?
I've already replaced the coolant level switch, hoping it would solve the flashing light, but it didn't.
Thanks

[kevtherev]

What engine is it?

does the light flash all the time?

the buzzer is low oil pressure.
check the connection to the high pressure warning switch (nxt to oil pump rear of engine facing the exhaust)

[andisnewsyncro]

If you earth the temp gauge it will (or should) go all the way over to the right, so it might be an earthing problem. Also possibly a problem with the low coolant module - looks like a relay, I forget the number at the moment. It may be a problem with the pcb behind the dash, but you're right to check it out....

Take the multi connector off and give everything a good clean and check for continuity. The buzzer is oil pressure so you need to check that too.

First of all I'd bleed the coolant and be sure the system is pressuring with no leaks and there's enough coolant in there. (Check the pressure cap - dalek cap- they're cheap to replace but buy a proper one from Brickwerks and you need to be sure that's behaving before you can bleed the system). Once you know the coolant system is good, drain it and refill it with a 50% mix of water & suitale antifreeze stuff - no point in doing that until you know it's not leaking out though.

Next step is a large mug of coffee and have a trawl through all the threads that come up from typing "cooling" or "coolant" etc into the search.,

Good luck

[Bonfireboy]

Cheers all.
I'll crack open the beers and have a search.

[AngeloEvs]

Since you have a buzzer of doom I am assuming you have a post 86/87 model van, if correct the may be the following will help.

A good starting point is to remove the module 43 (looks like a relay) mounted in the fuse/relay box under the glove compartment as this is simply there to trigger the LED in the event of coolant loss but, if faulty, can cause the temp gauge to swing over and start the LED flashing (if faulty this can happen as soon as you start the engine).
If the Temp gauge still swings over to the far right then the coolant LED will automatically start to flash as well to warn of 'overheating' - this normal.
You need to check the Temp sender in the thermostat housing and in particualr the connections to it. In the WIKI is an article that describes how to test Temp gauges at the fusebox. If you know how to use a mutlimeter and measure resistance you can use the connections detailed in the WIKI to measure the coolant level sender resistance - anything lower than around 50 ohms indicates high coolant temperature or faulty sender. Once you have the temp guge working correctly and the cooling system is functioning as it should then replace the module 43. Replacing it will then safeguard you against coolant loss.

The Coolant level sender itself cannot influence the operation of the temp guage needle so do not waste your time checking wiring to and from it - I would concentrate on the temp sender, cooling system and for any signs of botched wiring mods. Also note that there are two senders in the thermostat housing (plastic types) one is a switch for Heaters used in the choke, manifold and the other that faces the Cab is for the temp guage. The correct ones (one Blue the other Black) must be in fitted in their respective locations.

[Bonfireboy]

Thanks for that - I'll let you know how I get on.

[Bonfireboy]

Just come back in from the rain after a bit of tinkering.
Here are the results.

With Module 43.
LED flashes and continues to flash, temp gauge swings all the way to the right.

With module 43 removed.
LED flashes then goes out after a few second, and the temp gauge stays on the left.
But when I turn engine over - Light starts to flashes, stays on and temp gauge goes over the right.

I also measured the resistance - 42 ohms.
The engine turned over for less than 1min.

So does this indicate a problem with the sender?

[BALDY3260]

hi bonfireboy, can't give any advice sorry but what society are you with i'm east hoathly

[Bonfireboy]

Hello Baldy.
I've had many a night in East Hoathly!
Commercial Square - Lewes.

Just re-read my latest post - sorry for the bad grammar. Difficult to type with a wriggling 3yr old on my lap wanting to get on the CBeebies web site.

[AngeloEvs]

Sounds like you have two problems. Leave the Module 43 disconnected as this would appear to need replacing anyway.
With the ignition on the temp guage +LED appears to be working correctly (needle staying left and LED self testing then going out).

With ignition 'ON' only - everything seems oK untill you start the engine at which point the temp gauge circuit is faulty. This is a tough one and could be down to any number of faults. My next step would be to disconnect the wiring at the temp sender to isolate it from the sytsem and then to start the engine. 42 Ohms is far too low for your temp sender resistance and this needs to be checked with engine cold and any wires to it disconnected. On a normal temp engine the reading should be around 100ohms and significantly higher on a cold engine. There are other possibilities but best to tackle them one at a time.

[Bonfireboy]

Thanks AngeloEvs - looks like a Saturday morning replacing relays, sensors and diving behind the dash board.
Risking sounding like a right numpty - where would I find the sender that I will need to change?
I see from VW heritage and Justkampers there's an array of senders available. I just want to check which one I need before ordering.
I've got a diesel 1600.

I'm used to fiddling with cars (used to have a Triumph Spitfire in my early 20's) but its really nice to know that a complete novice to T25's can get friendly expert advice.
Cheers all.

[AngeloEvs]

I don't have any experience with Diesels but the sender is usually fitted in the thermostat housing, hopefully someone with a Diesel 1600 will give you the precise location and the part number. Once you have located the sender try disconnecting the wire that feeds to it (leave the module 43 out) and repeat the ignition 'on' test. The LED will self test for a few seconds and the gauge shouldn't move- Start engine - hopefully the Gauge will not move. With the lead disconnected from the sender take a measurement with engine cold and after warming up. The resistance should fall but no lower than around 100 ohms.

The Temp gauge and low coolant circuit warning is the same as for the Petrol other than the sender may earth through the thermostat housing if aluminium (Petrol thermo housing are plastic and therfore have two pins on the sender).

[Bonfireboy]

Yipeee - After changing the relay, pulling out the dash and cleaning up the contacts I'm proud to say I have a working gauge.. I think.
Need to take it for a drive to check if the gauge moves, but the light now goes out after self testing. An improvement.

[nesty]

Sorry to gate crash this thread. I have a kinda prob on my 1984 T25.

My temp gauge ok for a few seconds, thenthe LED starts falshing and the needle swings across to the hot. The coolant level is ok. Do I have module 43 relay on mine? Cuold this be the fault.

[andisnewsyncro]

Do I have module 43 relay on mine?

Have a look, it'll have 43 stamped on it in big letters