CDT 12v charging,shared FBH circuit diagram

[Snagger]

This simplified diagram shows the relationship between the CDT charging circuit and the Webasto Fuel Burning heater (FBH) where fitted, and it's dependency on the alternator for it to run with the basic factory set up, no remote , ambient temperature switching only.







This is how it functions, all components functioning correctly.

When the ign key is turned it feeds the charge lamp on the dash 12v to illuminate it. At the same time 12v is sent via the fuse board to the alternator to excite it (pre charge it) from the passenger side fuse board. (Green wire. to alternator).

When the key is turned to position 2 (start pos ) released and the engine runs, the alternator now generating it's own 12v supply, feeds via it's Blue wire, 12v to the ECU, which in turn ,via the Brown /Yellow wire from it, feeds 12v back to the charge lamp diode extinguishing it, thus confirming alternator function.

This connection Brown/ Yellow wire between the ECU and the dash is spliced (A125) in the loom. The 12v that was feeding the battery charge lamp is now shunted down this splice to the FBH thermal switch .

If the ambient temperature is +5 degrees C or less, the thermal switch activates, sending 12v+ from the thermal switch via the Green / White wire to pin no 1 of the FBH six pin plug. This is the start control voltage for the FBH, and on receiving it the FBH will go into it's start cycle and , if all is well, will fire up.

The FBH continues to function until the water temperature in the FBH reaches 76 degrees, when it goes into standby mode, ready to re activate if the two control temperatures air , water demand it.

This cycle will repeat as long as the air temperature and water temperature are within these boundaries. At any time the engine is stopped, the alternator will no longer be feeding the FBH voltage, so it enters it's shut down phase, to eventually switch off.

Hope this is of some use.

Happy New Year to all members,old and new.

Snagger

[stevenfloyd]

Originally Posted by Snagger

This simplified diagram shows the relationship between the CDT charging circuit and the Webasto Fuel Burning heater (FBH) where fitted, and it's dependency on the alternator for it to run with the basic factory set up, no remote , ambient temperature switching only.







This is how it functions, all components functioning correctly.

When the ign key is turned it feeds the charge lamp on the dash 12v to illuminate it. At the same time 12v is sent via the fuse board to the alternator to excite it (pre charge it) from the passenger side fuse board. (Green wire. to alternator).

When the key is turned to position 2 (start pos ) released and the engine runs, the alternator now generating it's own 12v supply, feeds via it's Blue wire, 12v to the ECU, which in turn ,via the Brown /Yellow wire from it, feeds 12v back to the charge lamp diode extinguishing it, thus confirming alternator function.

This connection Brown/ Yellow wire between the ECU and the dash is spliced (A125) in the loom. The 12v that was feeding the battery charge lamp is now shunted down this splice to the FBH thermal switch .

If the ambient temperature is +5 degrees C or less, the thermal switch activates, sending 12v+ from the thermal switch via the Green / White wire to pin no 1 of the FBH six pin plug. This is the start control voltage for the FBH, and on receiving it the FBH will go into it's start cycle and , if all is well, will fire up.

The FBH continues to function until the water temperature in the FBH reaches 76 degrees, when it goes into standby mode, ready to re activate if the two control temperatures air , water demand it.

This cycle will repeat as long as the air temperature and water temperature are within these boundaries. At any time the engine is stopped, the alternator will no longer be feeding the FBH voltage, so it enters it's shut down phase, to eventually switch off.

Hope this is of some use.

Happy New Year to all members,old and new.

Snagger

Hi Snagger,

Is this also for the 2001/06/ date of manufacture model as well

[stevenfloyd]

Hope that you can reply a.a.s.p to this post

[raykay]

The alternator feed to the FBH is the same for all years.

[Snagger]

Originally Posted by stevenfloyd

Hope that you can reply a.a.s.p to this post

This is the correct layout for the diesel 99 onwards as far as I know, I do not have access to later than 02 wiring diagrams.
This applies to the ZT as well, btw.

Snagger.

[danilo]

I was wondering if could find out if this could also be useful for a ’03. I have been trying to figure out these wire connections but I could just never get around to doing that. I know the alternator is connected to the ECU, the same way but I’m not so sure about other connections. Could someone please upload some wiring information of ‘03+ models too?

smt pcb

[Arctic]

Hi Ron.
Excellent thread mush appreciated