Heating in leisure vehicles has progressed hugely since the days of gas fires lit by matches. Motorhomes now have various systems, with externally flued gas and the option of being operated electrically, too.

In 1995, I remember thinking it was the ‘bee’s knees’ when our new ’van came with the gas and electric Carver Fanmaster. Posh or what?

The Carver 4000A Fanmaster we are looking at here is a development of the original. Many are still in use, offering reliable and efficient service.

We cannot stress highly enough the importance of having your motorhome professionally serviced every year, as safety items can and do fail. But what we will consider here is how to clean the externals of the Carver 4000A Fanmaster (I’m sure you’ve turned on the heating at some point to be met with a smell of burning dust or cremated spider!), and replacing the control switch on the heater.

The ’van shown here dates from 1999 and belongs to my parents. Some years ago, the sliding switch (which controls the speed of the blown-air fan) on top of the heater became faulty. The speed would not vary, so it was either running at full pelt or it was off.

After removing the unit from its casing, Dad sent it away for repair; it has worked perfectly ever since.

It is possible to open the switch unit up to clean various contacts, but unless you have a very good knowledge of electronics, that’s best left to the experts. If any controls or parts for your heating are faulty, one company that does repairs is A&R Electronic Developments. In the interests of safety, before doing anything else, ensure the heating system is turned off, and disconnect the gas and mains electricity supplies. Finally, disconnect the 12V battery (or batteries).

Tools needed to clean a Carver 400A fanmaster and replace the switch controls:

  • Cross-head screwdriver
  • Hand-brush and paintbrush
  • Duster and spray

Right from the start, every time we drove, the front of the heater ended up falling off (despite the dealer’s attempts to stop it doing so). Dad cured that with a bit of simple DIY. Securing two small pieces of wood to the unit above the heater, to stop it jumping up and off its mountings, solved the problem. Not pretty, but very effective. So our first task is to remove them.

Then, holding the bottom corners of the cover, gently pull these towards you. This should release the cover from its clip-on mountings. Be careful, as the cover can be fragile, especially where the clips are mounted.

With the bottom released, lift the cover up and over the gas control knob. The whole cover will then be free, apart from the electrical connections at the top. There is a multiplug at the cover end of the wires, which just slides off (if it hasn’t come off already).

Sometimes, when lifting the cover over the gas control, the knob is lifted too, and the control shaft falls off at the bottom end. If that happens, slot the bottom end back on to the spindle.

If you’re simply doing a spring clean, using the hand-brush and paintbrush, sweep between the fins on the heat exchanger, and in any other nooks and crannies you can see. Be careful not to be too vigorous around any of the wires or other connections.

Have a look around the flexible flue pipe to make sure it’s secure and there are no breaks in it. If there are, do not use the heater on gas until it’s been replaced or repaired by a professional.

On this model, a little yellow light on the gas control knob tells you if the gas is lit, but when the cover’s on, you can see the pilot light through its glass if you look carefully. So it’s worth giving this a wipe while the cover is off. Don’t forget the inside of the cover, too.

If the control switches are faulty, removal is simply a matter of removing the two screws. Replacing the controls is the reversal of removal.

With the controls in situ, give them a wipe. The same applies to the gas control. It’s surprising just how much grime collects in the recesses.

To replace the cover, the fiddliest job is reconnecting the multiplug. It should just slide on (when it’s in the right place), but don’t force it because you’re likely to bend (or worse, break) the pins. Make sure the wires remain above the heat shield at the top.

Next, slot the cover over the gas control knob, making sure you don’t dislodge the bottom mounting, and slide the cover down the panel behind until it slots into its upper mounting.

If it’s in the correct position, the bottom corners should just pop onto their studs. Again, don’t use force, as you’ll only break something.

With everything back in place, test the movement of the various controls. If all’s well, it’s time to reconnect the system’s gas/electrical supplies and finally, test the heater.

A step-by-step guide to how to clean a Carver 4000A fanmaster and replace the switch controls:

1. Mains switch in ‘off’ position.

Mains switch 'off'
Mains switch in ‘off’ position

2. Carver 4000A Fanmaster heater.

The Carver 4000A Fanmaster heater
Carver 4000A Fanmaster heater

3. Carefully release the bottom clips.

Releasing the bottom clips
Carefully release the bottom clips

4. Lift off cover with electrics attached.

Lifting off cover
Lift off cover with electrics attached

5. Slide off multiplug.

Sliding off multiplug
Slide off multiplug

6. Gas control shaft off the bottom connection.

Gas control shaft off the bottom connection
Gas control shaft off the bottom connection

7. Carefully brush out any dirt and debris.

Brushing off dirt
Carefully brush out any dirt and debris

8. Replace the gas control shaft.

Replacing gas control shaft
Replace the gas control shaft

9. Check gas control knob turns the shaft and bottom spindle.

Checking gas control knob
Check gas control knob turns the shaft and bottom spindle

10. Clean inside cover.

Cleaning the inside cover
Clean inside cover

11. Check operation of electrical controls.

Checking electrical controls
Check operation of electrical controls

12. Underside of the electrical controls.

Underside of the electrical controls
Underside of the electrical controls

13. To remove the electrical controls, remove two screws.

Removing two screws
To remove the electrical controls, remove two screws

14. Wipe around all parts, including pilot light inspection glass.

Wiping around all parts
Wipe around all parts, including pilot light inspection glass

15. Replace multiplug.

Replacing multiplug
Replace multiplug

16. Slot cover over gas control knob and onto mounting.

Slotting cover over gas control knob
Slot cover over gas control knob and onto mounting

17. Check operation of the controls.

Check controls
Check operation of the controls

18. Clipping bottom of cover to mountings.

Clipping bottom of cover to mountings
Clip bottom of cover to mountings and check all is working correctly

Looking for more DIY projects? Then why not take a look at these:

Future Publishing Limited, the publisher of Practical Motorhome, provides the information in this article in good faith and makes no representation as to its completeness or accuracy. Individuals carrying out the instructions do so at their own risk and must exercise their independent judgement in determining the appropriateness of the advice to their circumstances. Individuals should take appropriate safety precautions and be aware of the risk of electrocution when dealing with electrical products. To the fullest extent permitted by law, neither Future nor its employees or agents shall have any liability in connection with the use of this information. Double check any warranty is not affected before proceeding.

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