Engine coolant heater - temp sensor

[sidepod]

Any idea where it is? This is the <5 deg switch.

Ta v much.

 

[WelshGas]

Any idea where it is? This is the <5 deg switch.

Ta v much.

I believe it is behind the front bumper. Not sure which side but probably passenger side RHD.

 

[sidepod]

Ah yes. I found that one. I always assumed that was for the temp display.

I’ve not looked at the wiring scheme yet but I need to know if it’s just and earth switch of if it carries 12v?

 

[WelshGas]

Ah yes. I found that one. I always assumed that was for the temp display.

I’ve not looked at the wiring scheme yet but I need to know if it’s just and earth switch of if it carries 12v?

There is another Temp Sensor on the underside near the Waste Water outlet. I believe that might be for the Control Panel.
Sorry, can't help with whether it is 12v or switched earth.

 

[sidepod]

Ok. Everything I have relates to a 4 without the heater fitted so I’ll need to find the same sensor on the 5 wiring scheme. Layout is identical.

 

[AndyWT]

On my 2000 T4 Cali is behind the RH bumper, it a dumpy alloy coloured sensor, next to the black ambient sensor for the display panel, but depending on the build date one could be on the LH

 

[sidepod]

So I found this which seems to tie up with the Intel from the Butlertechnik site.

I still need to work out where the 12v source to “a” at the thermo switch is?

To be continued……

 

[AndyWT]

Here’s VW version of wiring which is slightly different to Eberspächer

 

[AndyWT]

Heres Eberspächers version which is very simple a, b & c is straight forward, VW just added a bit more complexity

 

[sidepod]

Excellent.

Found this.

https://t4-wiki.de/wiki/Zuheizer


This is the fuse I was looking for.

 

[sidepod]

So an update on this.

Following the wiring info above, I disconnected the 8 pin connector at the heater unit. It’s a bit tricky to get to. On the 150 unit like mine there is the inter cooler plumbing and AC pipe work that restricts access from above so it’s all got to be done from below.

So pins 1 and 2 confirmed 12v so fuse ok.
Applied 12v to pins 3and 4. Dosing pump ran ok.
Temp switch linked out.
Pin 7 showed 14.4v with engine running so alternator link ok.

All of this suggested the problem is not vehicle side but internal to the heater.

Stripped it off which was a bit fiddly but not too bad. Clamped off the coolant hoses but there was still quite a bit inside the heater, caught most of it thankfully.

Opened up the heater and checked the glow plug. Sure enough it was showing open circuit as suspected.
Popped in a new plug and rebuilt the heater.

I pulled the mounting cradle off the van and gave it a quick refurb.

Reinstalled the heater. Refilled the coolant. Linked out the temp switch and fired up the engine.
Sure enough the heater fired up.
I left it running but it tripped out after about 5 mins. Restarted the engine and it repeated, tripping out.
At this point I realised I had only cold air in the cabin, no sign of warm air!
Obviously an air lock. Found the bleed valve and sure enough a big splurge of air escaped.
Tried again and all works perfectly with hot air in the cabin.
Result.

 

[sidepod]

Next little job is to install a bypass switch so I can manually override the <5deg switch.
There is a intermediate connection for the temp switch in the battery compartment so no need to run wiring down the the temp sensor. Just pop some wires through into the dash and mount a switch.

 

[syncrostan]

Respect, that’s not an Easy job, did mine in the summer, but motor has failed.

 

[sidepod]

What made it tricky was the exhaust clamp was seized. This made it impossible to lift out of the cradle so I had to release a couple of the cradle mount fixings. Also the connector was stuck in the cradle.

Replacing was simple. Just slip the heater into the cradle and slip the clip over then connect everything up. Hopefully if it needs to come out again it’ll be a lot easier.

Spare motors are easy to source.

 

[sidepod]

So just to finish off….

This is the connector in the battery compartment.
I spliced into it and put a switch in parallel with the temp sensor so I can override it when I want.

Placed the switch in the column housing.
Done.