Switching for FBH - Earthing terminal 1 on CO925
 

Having studied the various circuit diagrams for the FBH control I believe switching to earth the terminal 1 on the connector CO925 will switch on the FBH.
Does anyone have experience of this - if I'm wrong please let me know. I'm reluctant to try this for fear of damaging the FBH.

Depends on which FBH you have, some are triggered via an earth, some use +12v.

There are only two variants of the FBH fitted to the 75, most are later model 98570B, early cars had a model 66232C, you need to be certain which model you have when testing. The model number should be on the Webasto sticker on the side of the heater.

Connector CO925 being the 6 pin plug on the top of the heater, to start either and/or use as a parking heater:

For 98570B - its earth to Pin 3

For 66232c - its +12v to Pin 1

And yes plenty of experience doing this by lots of members on this forum ( mainly with the 98570B which most members have )

In the How To section you should find a How To on taking the 6 pin connector apart.
If it is not in the How To it is somewhere on the forum

macafee2

Gentlemen many thanks for all the information - seems I got it wrong but thanks to the knowledgeable forum members I have some direction to having a warm car when my wife needs it. The other option is to wait for the temperature to drop to 5C which does not go down well.
I will report back when I have completed the extra control to my FBH

With some extra wiring you can also connect it to your ATC so the cabin is warm when you get in the car after starting it remotely

On my 2003 ZT-T Diesel the FBH used to work perfectly, but this winter it somehow stopped working completely.
When activated (by the timer or remote) Nothing happens, not even a click or anything.

By switching it manually (pin 3 to ground) the same... nothing..

According to the schematics, there's 12V and ground at the 2-pin connector, and there's 12V on Pin 1 (If i'm not mistaking, haven't got the schematics at hand).

But... nothing happens... all fuses are (obviously) ok..

So.. PCB dead ? or could something else be a problem?

PCB, water pump and glow plug. I don't have it to hand but on the forum there is a guide to running the FBH and fault finding. For example if this happens and then at x minutes this happens then this is faulty.

Have you a good multi meter, test what ohm resistance you get across the glow plug wires and report back. A member can then tell you if it is faulty or not. I cannot recall if less then 5 ohm or 0.5 ohm is good.

frenchmike or devilish both members here can test and repair the pcb if required.

macafee2

First of all take a look at this and decide if you have the early or late model FBH https://www.the75andztclub.co.uk/for...d.php?t=310873

The 98570B takes 12 v to pin 1 and earth to pin 3

The 66232C takes 12v to both pins 1 & 3

Once you know which one you have you will know whether the test you ran by putting earth to pin 3 was a valid one, if you have the 66232C you can now try 12v to pin 1

If you have a remote I would expect both pins 1 and 3 to be populated in the 6 pin plug

Just to eliminate any issue with your remote set up, start the car when temp is 5 degrees or below and see if the heater works in supplementary mode

If after trying the above your fuses are ok and you have 12v and earth to the 2 pin plug and the heater is still completely dead than your PCB needs to be fixed or replaced