Webasto 3500 Airtop

[Laundryman]

My unit was professionally fitted 10 years ago. I’ve owned the boat for 3 years and the unit has been used most weekends (before the current heatwave). It has now developed a fault, the flashes signalling a problem with the glow plug. I see little point stripping the unit just to replace the glow plug and would most likely do a full service. The kit for this is around £250. More if I send to an accredited Webasto repair centre. Question is, Is it time to replace it or do I proceed with the repair and hope that nothing else fails?
Second question, is the installation of a new 4kw or even 5.5kw unit a straight swap? How much work is involved in changing it. I only have the simple rotary controller, nothing digital. I should say that the old one provides plenty of heat through the 4 outlets but I may as well improve things if I’m changing. Is it time to replace or repair. Thanks. Alan

 

[vyv_cox]

I know nothing about your particular unit but my first move would be to check all wiring and connections to the heater. My Eberspacher is used rarely but was failing to start, also suggesting glow plug problems. I found a connector in the stern locker close to the heater, heavily corroded. After cleaning this up the heater works perfectly. The current taken by the plug at start is quite high.

 

[pcatterall]

The 'kit' sounds expensive. I repair Eberspachers rather than Webastos but my usual strip and 'service' parts costs are sub £50.
Unless a major component requires changing then the costs are limited to the glow pin gauze screen and new gaskets.
You may find that it the glow pin or screen is carboned up rather than faulty.
I would remove the unit, separate the bits and give it a good clean, testing the components as you go.
Fitting a bigger heater may require a fuel pump and possibly larger ducting, the rotary control may work across bigger models.

 

[dod]

My unit was professionally fitted 10 years ago. I’ve owned the boat for 3 years and the unit has been used most weekends (before the current heatwave). It has now developed a fault, the flashes signalling a problem with the glow plug. I see little point stripping the unit just to replace the glow plug and would most likely do a full service. The kit for this is around £250. More if I send to an accredited Webasto repair centre. Question is, Is it time to replace it or do I proceed with the repair and hope that nothing else fails?
Second question, is the installation of a new 4kw or even 5.5kw unit a straight swap? How much work is involved in changing it. I only have the simple rotary controller, nothing digital. I should say that the old one provides plenty of heat through the 4 outlets but I may as well improve things if I’m changing. Is it time to replace or repair. Thanks. Alan

Good Morning sorry to learn you are having some trouble with your heater. As I have the same heater I will try to offer some help.
First you say your control is flashing indicating a glow plug problem. From personal experience this is not always the case. A check on battery current should be made first to determine if it is sufficient to start the heater (also suggested by vyv cox)
If there is enough current then next check the fuel pump is ticking on start up. All ok then next question is did you have much smoke from the exhaust when it was working. If so a decoke is needed. (means taking the unit apart and cleaning)
As you mentioned the cost of replacement burner is expensive and a service from a dealer will also be expensive. So DIY is not difficult and as I found only a decoke was necessary.
Word of warning, once cleaned, make sure the fuel nozzle is clear by blowing air through it (this is easily blocked)
NOTE : Take care removing the exhaust from the unit. This will be tight and needs great care to remove without breaking (took me 1 hour just to do this) Total time to do job was 3 days (i to remove unit ,2 clean and decoke burner
etc., day 3 to restore and fit uniy)
I must add that I am not an expert and had no knowledge or experience of these heaters prior to doing the job. What prompted me to try was the cost of spares and someone else's tale of a very expensive service.

Good luck

 

[rotrax]

Result! Well done,