water-red light flashing Sometimes

[Pootle]

Many thanks for all your advice.

I've just removed the two earth crowns behind the fusebox and cleaned them up. The rear one did have a little corrosion, not surprising since it hadn't been touched for 20 years! I squirted contact cleaner on the spade terminals and squeezed some of the connectors together gently before reassembling, and gave the whole lot a squirt of silicone grease afterwards.

I'll let you know if this fixes the problem.

[asahartz]

Now I know my bus is somewhat different in this area, but the gauges & senders are still original.

The red light flashes, I believe, when the radiator gets hotter than it should be - not the engine? That's how mine seems to work now (module & engine bay wiring permanently removed & modified).

So perhaps check the sensor on the radiator?

Hopefully I'm not barking up the wrong tree here.

[AngeloEvs]

Temperature coolant LED is activated when the coolant temp sender in the thermostat housing falls below 50 ohms and is not affected by or connected to RAD thermal switches, these are for the fan only.

[Pootle]

Temperature coolant LED is activated when the coolant temp sender in the thermostat housing falls below 50 ohms and is not affected by or connected to RAD thermal switches, these are for the fan only.

Does the LED flash when the coolant level senser in the expansion tank detects no water (so presumably goes to a high resistance) AND also flash if the temp sender in the thermostat housing falls below 50 ohms when the engine gets too hot?

Presumably if the temp needle is in the right place we can rule out problems associated with the temp sender?

My cleaning of the crown earth made no difference, so I cleaned the main earth point at the battery strap - that made no difference either. Next weekend I'l have a good look at the earth in the engine bay.

[clartsonly]

the water red lght sometimes stays on after start up, turn off then start up again it goes out, i have read the wiki about the red light faults/ what it could be,
the water gauges does rise up after she's been running. is it anything to worry about as i'v got to go Cov to bolton on sat,
any help with this issue,

I havn't read all three pages so am not sure if you already have it solved but mine does the same I put it down to a bad earth, if it is any help the wiring no longer makes my light flash at all if I remove the plug from the switch, after a restart. I find myself starting then waiting for about 5 minutes on the journey then quickly off and on again whilst travelling.

[AngeloEvs]

Does the LED flash when the coolant level senser in the expansion tank detects no water (so presumably goes to a high resistance) AND also flash if the temp sender in the thermostat housing falls below 50 ohms when the engine gets too hot?

Yes to both! The high resistance due to loss of coolant in the header tank is sensed by the Level Sender Control Unit 43 in the fuse box and this in turn triggers the LED. Removing 43 disconnects this function and if the LED stops flashing then the fault is with the level sender circuit or loss of coolant.

[clartsonly]

cleaning the crowns started all sorts of things that didn't work before.
I dont see why the intermitent problem of when it starts it continues to flash but off and on again once started stops it flashing.

[AngeloEvs]

Bear in mind that once the LSCU module 43 is triggered it will continue to flash the led untill the ignition is switched off and the module is then re-set. Yours sounds as though it is being triggered the instant you start. Switch the ignition on and leave it on without starting the engine. Does the LED stop flashing after a few seconds (the self test is in the gauge and should stop after a few seconds) but if it continues flashing you need to do the following:-

Remove the module 43 from the fuse box and do the same again, if it now stops flashing after the self test period then the fault is most commonly traced to one or more of the following:-

low coolant
Poor crown earth
poor battery earth
faulty LSCU module (marked 43)
poor connections at the Level Sender or at the earth under the coil
poor connections at the Level Sender
Poor regulator/stabiliser (sudden volatge changes can trigger the module)

[chickenkoop]

when i posted this i had a problem, however as a week passed i would switch the ignition on and wait 30sec, then the red light stopped coming on, you tell me, and now i just wait till the yellow glow plug light goes out and start her, still no red light, fingers crossed,

[ryoc]

Mine was dodgy wiring to the switch. Replaced with new spade connectors, ok now.

[clartsonly]

this is very helpful as I am sure I remove the "module" relay I assume 43 from the fuse box before this issue started in the first place.. whilst I was trying to sort out rad fan.

[Pootle]

I've still not fixed this problem. The earths front and back are all as shiny and new now.

I want to try replacing the LCSU (part no 42, location 3 in the relay box). Does anyone know where I can buy a new one? I've looked in the usual places. I would prefer not to buy a secondhand one in case that's faulty too.

Part number is 191 919 376A.

Thanks!

[AngeloEvs]

Modules 42 and 43 can be used (same function), often sold on Ebay very cheap and 42 should still be available from VW but expensive, (available last year at about £27-00).

If you are absolutely sure that this is not a low coolant fault then you could remove the module 42 and see if the fault continues. If the fault seems to be cured with 42 removed then you can concentrate on the coolant level circuit connections/components.

[Pootle]

Modules 42 and 43 can be used (same function)

Does module 43 have the same part number as module 42 - 191 919 376A?

[AngeloEvs]

Not sure, I quoted the part number for a 43 and they checked on their computer and told me it was available on order only. When I collected it it was a 42 type and was told that it was an alternative but direct replacement. Why not PM Billy739, sure he would have one. Usually, these modules work or don't rather than be intermittent so I would try a second hand one first just to eliminate it. I updated my last post so check that too.