Webasto Intermittent Operation

[PrevostNewbie]

Limited tool? not really, having the test box allows me to fully test every function of the Webasto independently while i am standing right there in front of it. Think of it as having a multi meter at your disposal when diagnosing an electrical problem.

[shahzadlateef]

Thanks Mike. This is really helpful. May bite the bullet ($500) and get tester and pressure gauge.

My thought on limited use was that this is the first issue I have had with Webasto in over 3 years, so a specialized tool may be just sitting. You are correct that it is a good tool to have in the toolbox so I am not looking around when I need it.

Happy Holidays

Regards, Shahzad Lateef
2003 Marathon H3-45, DS

[shahzadlateef]

Replaced all three sensors and the heater still did not kick on (same issue as before). Will test in the morning to see if it still kicks on when it’s cold outside. On to next phase of troubleshooting. Will purchase the test box to see if i can isolate the problem.

I went through the invoice notes from Marathon from October 2022, and it stated the following,

”Ran unit, it fired but smoked heavily. Performed complete service. New fuel nozzle and filter, cleaned photo eye, repaired fuel leak on supply line. Ran unit on 12V heat and 12V water heater until unit cycled. Unit now working as it should. Next morning unit failed on third firing. Tested with no signal from ignitor. Bled system of air so it would not overheat. Fired and ran for 2 hours on water heater.”

Two things stick out. One heave smoke. I had noticed it as well when it works. It is white smoke only on initial cold startup. Second was no signal from ignitor.

Will clean the electrodes ignition sensor tomorrow and see if that replicates what Marathon found. Something to do while I wait on the test equipment.

Regards, Shahzad

[Fratto]

Two things

1) it is not unusual for them to smoke on start up when they have not run properly the prior time. There is a lot of fuel and stuff in the exhaust pipe and it takes some time to burn it all out. After it has run properly for awhile there will be limited if any smoke on start up and no smoke while running.

2) Marathon says that they bled the air out so it would not overheat and then it fired. So did it overheat and if so why? Was the cause of shut down on 3rd firing?

[shahzadlateef]

Update 2/21/2023 - Finally received the Webasto testing equipment. Once the outside temperature was high enough, I ran the heater and it did not ignite. I connected the test equipment. Battery, flame sensor, motor and circulator pump all tested fine. Solenoid also clicks when engaged through test equipment. The ignitor did not respond to the test equipment. I removed the ignition coil and electrodes, cleaned connectors and re-gapped the electrodes. Once again it failed to run. Leads me to believe that it is the ignition coil that is not functioning properly when outside temperature is above 50 degrees. I don’t think there are any serviceable parts within the ignition coil unit, so I will order a new unit and replace it.

Thanks for the links to test equipment.

[Fratto]

If the igniter will not fire on the tester then I agree that it is likely bad. However, I dont know what the outside temperature would have to do with it.

[Hoffman]

Any electronic component can be temperature sensitive. However it usually indicates an underlying structural failure in some internal component. Cold (or heat) can cause existing cracks in circuit boards to expand/contract leading to intermittent failures that are observed as temperature dependent.

[shahzadlateef]

Continuing to chase the Webasto gremlins. With the outside temperature below 50, I was able to get the ignition coil to fire. I also checked the fuel pressure and it registered 150psi. With both fuel and ignition working, I closed the unit and it will not fire using test equipment.

With the unit open, I can see the arc across the electrodes. I can also see the fuel spraying out of 0.35 nozzle. Again when I close it up, it wont fire up.

First thought is to change the nozzle to see if it is not properly vaporizing the fuel? Any other thoughts?

Regards, Shahzad Lateef

[bussphart]

Call Rudy in Texas and he'll steer you in the right direction. Got his contact information?

[shahzadlateef]

Found Rudy’s information from a previous post (For reference his phone number is 713-818-3234). Will call him tomorrow.

Thanks. Shahzad