refurbing and fitting a webasto thermotop C/Z

[lloydy]

Seems to be very little known about these heaters, so the one i have here i'll strip down and decoke. It will be fitted to my van with a loom and relay to control the vehicle fan. Toasty warm starts!
For those that don't know this is a coolant heater that runs of diesel and can be wired to bring on the vans heater blower and defrost the screen ect. It has a inbuilt pump, so runs independent of the engine. long term plan is to get a webasto oval timer and some sort of remote start, either gsm or the garage remote type
So, this is the unit

close up of the data badge showing its 5kw

i asked for a pigtail of the original plugs just in case i decide to make up my own loom, unlikely though as a premade one is not much more expensive.

And this is the coolant pump

[lloydy]

have been researching the pin outs on the 6 pin control plug.. you can just see the numbers on it here


1 = power on 12v+ this is normally wired to a thermostat that fires the unit up if the ignition is on and the outside temp is under 5deg. Opinions seemed divided if this brings on pin 4 so you can control internal heater fan via a relay

2 = rover diagnostics

3 = if this pin is earthed the unit fires up, seems to be a test mode and it also brings on pin 4

4 = output 12v+ can be wired to a relay to bring on vehicle heater blower

5 = unused

6 = output to fuel pump 12v+ pulsed supply

there is a separate plug for the main 12v supply

[max and caddy]

What's it off? a vw product like a touran or similar?

[lloydy]

from a rover 75, by far easiest available one.

[lloydy]

Looking at the ready made looms available, none of them really tie in with how i want to wire it. And i don't see the point of paying £70 for a loom and then having to adapt it, so..... I am going to do it myself and try to make it look as factory as possible.
To that end, vw relay plate and vw fuse holders are on their way, these will clip to the top of the standard fuse/relay box
one of these

and 3 of these

the way i want to wire it is to still have the rover outside temp sender, so the unit will work as a aux heater and come on with ignition and run up to 77 deg, as long as the outside temp is 5deg or below.
Then i will wire in a gsm activated relay, so i can turn on the unit remotely and defrost cab ect (this is the parking heater mode)
gsm relay i got was this one

as you may be able to see, it has a second relay, trying to think what to use this for (if anything) maybe to fire the eber?
well... that the last of my birthday money gone!

[lloydy]

Ok, so time to give it a service..... surely it's just like a miniature oil boiler?.... thankfully on breaking it down, it is

First up is to remove the pump, need to remove one part of the control cover

exposing some plugs, you can see where ive unplugged it already

one screw here to undo, then the pump comes off


stand the unit on its end, then the 5 black screws visible below need to be undone

The top section then pulls off, just need to be careful with the small fuel feed pipe as it passes through it's grommit

you are then looking at the the burner fitted into the heat exchanger

remove the rubber seal

close up of the glow plug and retaining clip, you can also see a black screw directly below it. there is 4 of these around the burner which you can see better two pics above. Undo these and the burner pulls out

burner out

glow plug removed

view down into burner, where you can see the wire gauze the diesel soaks through, the glow plug fits just in front of this. As you can see there is a bit of soot in there, but to be honest it's pretty clean

i then gave it a clean with a blunt screwdriver, looks a bit better now and you can see the holes around the edge now

what came out

All i want to do now is rig something up to give the glow plug 12v to make sure it works, and maybe do the same with the pump then it can be rebuilt.
Will then connect it to some pipework and test run it, here's hoping the pcb is ok..........

[lloydy]

New webasto fuel pump turned up today, no idea why no one bid on it but it cost pennies
Didn't really believe it until it turned up, even came with a VW rubber mount

[max and caddy]

Probley no one bid because they are very reliable and never go wrong! Also only certain versions have them and they are less likely to be repaired now as the heater is likey the suspect.

[lloydy]

probably very true, nice for me though.
I just hope the pcb is good on this one, as that will be a pi$$er. Although i have found a guy on a rover75 forum who can repair the circuits.
Cleaned up the pump.. four screws to undo

leaving you a view of the impeller, can just see the snap ring holding it on to the spindle

snap ring removed

and impeller comes off

this just needs a wash and any grit/rust cleaned off so it spins freely on the spindle. Just don't tell the wife i did it with the dishes...

fingers and toes crossed it fires up! just need to blag some 3/4" hose and connect it up to a bucket of water..

[lloydy]

Well, the good news is the glow plug works
Have wired myself up a Hicksville wiring loom, so that's already to go (bullet connector is to simulate call for heat)

[lloydy]

And the wife just walked in with my gsm relay

[lloydy]

Managed to bag some webasto coolant hoses off ebay, only 6 quid!!

[lloydy]

So, it was all going to well.... rigged it all up to a tank of water, all looked good but no ignition symptoms point to a component on the pcb.
found some guy on the rover 75 forum who repairs them for £44 posted, so its now boxed up ready for posting. To remove pcb,
four screws here

pull the plugs on the right out, and undo the torx screw

pcb now comes away