Webasto heater problems
 

Hi
I fitted a Webasto engine heater some years ago - I don't have the control unit, so did the forum "bodge" and wired the green pin 4 wire (from memory: I think that's right!) to an illuminated earth switch. To switch on, I operate the switch, earthing the wire and triggering the unit. As a side question, it is a latching switch - would a simple "push to make" one have been better?
The issue is that the unit is switching itself on! Whilst driving, I noticed that the switch light comes on intermittently, usually dim, not full brightness, from time to time, and I think I can smell the Webasto exhaust. Is it an issue with the Webasto, or the switch? Any advice would be gratefully received.

I think the switch needs to be a push on, push off switch and it needs to remained earthed while you want the switch to activate the heater.

if you earth the webasto, does it start and run normally/as it should?

macafee2

Pin no 4 gives out 12 volts only when the heater is running,it normally used to start extra add ons.Tom

If I press the switch with the engine cold the Webasto fires up normally. As far as I know it has been working fine for years! Tonight after driving 20 miles the illuminated bit of the switch lit up faintly, then as it flashed briefly fully on the SatNav lost power. The illuminated switch periodically glowed, and stayed on for a while after I turned the ignition off.

Tom, when you say add on's do you mean the webasto timer?

macafee2

wild guess, sorry if no help. Poor or inappropriate earth or inappropriate 12 due to chaffing wire?

macafee2

Something wrong with your memory, as Dinky said, there is no way you are earthing pin 4 to start up the FBH

Is this a typo, should it say 'and the satnav lost power'.?

The type of switch matters diddly squat.

Where have you taken the 12v supply from to illuminate your manual on/off switch?

Do you turn FBH on as parking heater, auxiliary heater, or both?

If you are having spurious power problems, cut the Kbus wire (pin 2) near the 6 pin connector.

Yes that is correct,you can connect to your AC system via relays etc,12v from pin 4 only when heater is running,pin no 2 is for diagnostic connection,pin no 5 is not used. But I stand to be corrected,French Mike will Know.

Thanks for all the info. Update!
Yes, my memory is shocking - if it happened after 1975 I'm in trouble . . . .

I just remembered, the Webasto worked fine for years, then died and I had it replaced with one from eBay last year - I'm wondering if it's a different type, and this is the root of the problem? How do I tell, please? There are two plugs on the Webasto: one has 2 wires - black and orange. The other has three wires in a line left to right - blue, white, grey/green, and a 4th brown below the blue. The blue has been cut, and connected to a (green!) wire that has been added, going through the illuminated switch to earth. I did say I have memory problems :-(

The unit fires up, heats for 10 minutes then switches itself off if I press the switch, but the illuminated switch was half coming on sporadically - it now stays on "dim" all the time, irrespective of the ignition switch. There is no separate supply - the light is in the switch, and illuminates when it is "on". Is there a fuse I can remove as a temporary solution?

I'm not able to do much myself, and am having trouble finding an electrician to look at it - is there anyone I can pay to sort it if I come to you, please?
I think the satnav (yes, it was a typo!) issue is unrelated - the satnav wire plugs into a cigarette lighter socket wired to the battery, but this is dangling on top of the plastic cover above the pedals, next to the place where the Webasto switch is mounted, so maybe I disturbed it trying to investigate the Webasto?