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Old 11th January 2015, 14:36   #1
rich17865
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Default How To Strip and Rebuild the Fuel Burning Heater

I have had chance to fully service the FBH, and took a lot of pictures along the way.

You can also use this thread for detailing how to strip down and replace the glow pin if yours has failed.

You will need,

Webasto service kit 9000861A for ThermoTop Z/C



These are available from Bowers, as are any other parts that you may need for your FBH

Philips screwdriver, slotted screwdriver, torx screwdrivers T10, T15, T20, biological washing powder, large washing up bowl and an old toothbrush.

With the FBH removed from the car and ideally on a worksurface,

Remove the spring clip from the inlet silencer, and remove the inlet silencer.



Now remove the four philips screws holding the black plastic cover on the top of the unit.

This will uncover the printed circuit board.

Unclip the next plastic cover on top, this will uncover the plugs for the pump, fan and glow pin.

Unplug the three plugs, no need to note which holes they go into as they are keyed and will only go into the correct hole upon reassembly.

Remove the torx T15 screw in the circuit board and remove the spring clip, you can now remove the circuit board. This can be sent to FrenchMike for repair should it be necessary.

With the two covers removed and circuit board removed also, the FBH should now look like this.



There is no need to remove the third plastic cover unless you are having problems with the blower fan. Fan problems are unlikely as the FBH has an inlet silencer fitted which stops detritus getting into the unit.

Remove the water pump wiring from the recess.



Remove the torx T20 screw from the water pump clamp. Discard the screw.



Loosen the spring clamp for the water pipe from the FBH to the water pump, then remove the water pump.





Remove the following torx T20 screws. Discard the screws.

Three shown here,



One here,



One here,



Now you can separate the blower motor housing and blower fan assembly from the burner and heat exchanger. Be careful as the fuel pipe fits through the housing and is attached to the burner assembly.



With the blower motor assembly removed, you can see the burner chamber and heat exchanger. Note the fuel pipe sticking up.



Remove this seal and discard it.



Lift the glow pin wiring grommet out of the body.



Remove the four torx T20 screws from the burner assembly. Discard these screws.



Lift the burner assembly from the heat exchanger.



You can now remove this spring clip and withdraw the glow pin.



Remove these four torx T20 screws.









You will now be able to separate the exhaust section from the main heat exchanger body. You will be able to see a even coating of soot with often some ash in the bottom of the heat exchanger.





The two water pipe connections and the main body parts are sealed with these seals. Note that these do not come with the service kit above and need to be kept for reassembly.



If you take a look at the burner assembly, it may seem clean at first inspection. However, look carefully inside as you will be able to see large bits of carbon inside.







Carefully scrape away as much of this carbon as possible. This is the cause of a smoking FBH and also non starting FBH (assuming the PCB is working). There are a number of small airway holes inside that are vital to the proper combustion that get clogged and bust be cleaned.

Be careful not to damage the metal gauze in the bottom of the burner assembly. It is non replaceable and will result in you needing a replacement burner assembly!!

You can see here some of what was scraped out of this one.



Take the heat exchanger, exhaust section and burner assembly and put them in the wife's best washing up bowl.



Put in about half a mug of biological washing powder and fill with very hot water until all of the parts are covered. You will see the washing powder start to dissolve the carbon straight away.



Leave the parts in the mixture overnight, or until the water and bubbles stop moving of their own accord. When the washing powder can do no more cleaning, it will look like this.



The cleaned parts will need a little agitation under running water with an old toothbrush and the carbon will just brush away, leaving you with clean parts like this.





You will need to run the burner assembly under the water too, making sure to scrub inside thoroughly with the toothbrush until bits stop coming out in the flushing water. Make sure that any holes you can see are clear of carbon.



MAKE SURE YOU RINSE ALL THREE PARTS IN PLENTY OF CLEAN WATER TO REMOVE ANY TRACES OF WASHING POWDER

Take the water pump and remove the four torx T10 screws holding the two halves together and separate the pump.



You will see the impeller, held down with a C clip.



Carefully remove the C clip and washer and lift the impeller off the spindle. Be careful as there is a second washer on the spindle under the impeller.



Clean the impeller and pump and reassemble. This one was quite clean, but you may find a lot of scuzz in there.



Take the heat exchanger and exhaust assembly. Carefully refitting the rubber seals you saved from earlier.



Screw the two halves together using the long torx T20 screws. You will notice they are similar to the PCB screws, so make sure you are using the right ones as they have different thread pitches.



Refit the glow pin to the burner assembly, and refit the clip.



Now fit the new burner assembly gasket. It is very uncommon for these to be reuseable.



And refit the burner assembly, using the new screws supplied with the service kit.





Re route the glow pin wiring, fitting the rubber grommet to the body.



Take the rubber gasket and fit it to the blower motor assembly, there are locating pegs and only fits one way. The green paper gasket is not used for this type of FBH and can be discarded.



Replace the fuel pipe rubber seal with the new one supplied with the service kit.





Screw the blower motor assembly to the heat exchanger / burner assembly using the new screws. Remember that the fuel pipe fits through the blower assembly, so be careful.



Refit the water pump, pipe clip and pump clip. Screw the pump clip down using the remaining new screw.



Reroute the water pump wiring.



Refit the body to PCB gasket.



Refit the PCB, the spring clip and torx T15 screw, plug in the wires and refit the PCB cover with the long philips screws and then clip on the plugs cover.

Finally refit the inlet silencer and spring clip.

The FBH is ready for refitting to the car.

There are no photos of the PCB removal or refitting as the FBH I stripped was missing this part. I am sure you can work those bits out for yourself

EDIT:

It has been brought to my attention, thanks to bartonrover that there is a variation to the burner assembly for the earlier FBH unit.

The glow pin is not held in with a spring clip as per my photos above, it is held in with a threaded stud that has an allen key hole in the end and locked into place with a nut. There is also a very small metal plate that fits on the glow pin, which I assume is a spreader plate so that the threaded stud doesn't damage the glow pin when tightened up. Be careful when removing it as it could be easily lost.

See the following photos,









Disclaimer:
You are responsible for any work or modifications carried out on your car and you undertake any such work at your own risk.
The 75 and ZT Owners Club nor the original author of this How-To can be held liable for anything that may happen as a result
of you following this How-To.

Last edited by rich17865; 8th February 2015 at 19:58..
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Old 11th January 2015, 15:24   #2
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What a great write up as usual!
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Old 11th January 2015, 15:30   #3
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Indeed, your 'enthusiasm' knows no bounds and benefits the wider membership greatly. Thank you Sir!
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Old 11th January 2015, 15:40   #4
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I don't even have a diesel
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Old 11th January 2015, 16:04   #5
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Quote:
Originally Posted by rich17865 View Post
I don't even have a diesel
Well not any more .

Brilliant how to Rich, thanks , saved for posterity here
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Old 11th January 2015, 16:16   #6
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Fantastic "How-to" Rich!

Almost makes me want to buy a diesel!
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Old 11th January 2015, 16:26   #7
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A fine write-up and great to see photos in focus too! Who is it on the Forum who reconditions these and sells them? I don't have one but I could really appreciate it!
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Old 11th January 2015, 16:36   #8
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Quote:
Originally Posted by MrDoodles View Post
Fantastic "How-to" Rich!

Almost makes me want to buy a diesel!
No need to buy a diesel Mark.......you can refurb mine
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Old 11th January 2015, 17:07   #9
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Excellent how to, thanks. I may need to do this to one of my units as it did not work
so will follow the how to carefullt along with Harry's


here is a link to the service kit rich mentions
http://shop.airconcoparts.co.uk/9000861A

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Old 11th January 2015, 17:07   #10
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I'd done a service on my own last year, that's a great write up and fabulous pictures,
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