Webasto overheats and shuts down

January 17, 2020, 04:42:52 pm

I have been impressed with this new forum's search function.
I have been working to fix a problem with the Webasto system in my 2000 Magna for the past two months and finally arrived at the fix 2 days ago and the system is now working great. I am writing this to document and possibly help others in future Webasto problem searches.

Problem:
Initially the unit wouldn't light off. Performed an annual tune up (fuel nozzle, fuel filter and ignition electrodes) and solved that. The unit then lit off, ran a couple of minutes until it overheated and shut down. The temperature limiter and overheat fuse had both blown. Both of these are located under the cover on the top of the burner can. The temperature limiter has a red reset button which can be reset when the temperature gets below its limit. (There is another temperature limiter that may be installed that will automatically reset.) The overheat fuse cannot be reset and requires purchasing another fuse (approx. $50). With a multimeter you can verify whether anything has blown by testing for continuity individually with each of the 3 sensors under the cover. If each sensor/fuse has continuity between its wires and all three have passed the continuity test the fuel solenoid will be allowed to open. No continuity, no fuel. After buying and replacing the overheat fuse I blew it again on the next start. With some advice from Sure Marine who sells Webasto parts, I cut the wires for the fuse which again gave me continuity and allowed me to continue troubleshooting. I will again replace the overheat fuse after fixing the overheat problem.

On each start I was now getting a good start and light off but the unit would overheat and shutdown after a minute or two. The pump behind the Webasto unit seemed to be working fine and I could feel coolant moving in both the "in" and "out" hoses but the coolant hose coming out of the Webasto wasn't getting hot at all. I also checked the pump in the electrical bay just forward of the first bay compartment and it also was running fine and coolant felt like it was moving in both hoses. There is a thread on this forum from 2007 that exactly described these same symptoms. Like the poster on that thread I decided I had an airlock in the coolant line that wasn't allowing the coolant pump to push coolant through the Webasto to heat the coolant and cool the burner can. As I worked my way through the steps he had performed, I replaced the coolant air vent and then performed a coolant change (it was time anyway). The problem didn't change although it took a little longer to overheat and shutdown.

After 2 months of troubleshooting this in my mind as I was going to sleep and waking up in the morning I was down to 2 additional things to check before giving up and paying someone else to figure it out. I had previously replaced and later repaired the coolant pump in the electrical bay in the first bay after it sprung a gusher and later refused to quit leaking. I again checked that pump and coolant hoses, discovering the hose out of the pump was connected to the hose running aft and the "in" connection to the pump was connected to the hose running forward.

Solution:
After checking and confirming the direction of coolant flow via the Country Coach system drawings, I switched the hoses at the pump so the hose going aft was connected to the "in" and the hose going forward was connected to the "out" connection. Not a clue how or when I had connected them incorrectly but what was happening was the two pumps in the Webasto system where pumping against each other and the coolant wasn't moving. The thread in '07 ended with figuring out that one of the solenoids in the plumbing bay was screwing up which was fixed by cutting the wires and planning to deal with fixing the solenoid issue later. If I hadn't discovered this pump/hose issue I was headed there as a last option. This was certainly an easier place to work.

Bottom Line:
In this case I created the problem by connecting the coolant hoses incorrectly to the pump. It is an easy thing to do especially if the pump is completely removed for replacement or repair. It's also true that same issue could easily have been caused by a repair shop if they had been working in the system, and It could be an issue with any of the 4 pumps installed on the coach. Just another thing to check if you are having similar issues. It was 2 months of frustration but a real learning experience about the Webasto system.

Dan
2000 Magna #5788

Re: Webasto overheats and shuts down

Reply #1 – January 17, 2020, 11:45:15 pm

Dan - 1st, concur with the wonderful benefits to the enhanced search function!!!

After that, thanks for closing the loop back on what the problem was... My DW, has taught me over the years... That when problem solving something that had been working fine - to go back and look to see what I may have inadvertently 'messed up'.... (That advice, has saved me many a post for help!!).

Glad all is well, best,
Smitty
04 Allure 31017

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