Webasto heater in Mazda6

[baovit]

Hello,
Maybe someone has experience and knowledge with Webasto ThermoTop heaters and can help me? I have factory fitted ThetmoTop Z heater in Mazda6 diesel automobile. It should start automatically in temperatures below +5 C. But last winter it started to fail starting at all or turn off suddenly with lots of white smoke. First I thought that it?s because of glow plug. Heater is connected to cars diagnostic bus and I can read fault: Glow plug circuit short to ground. So I disassembled heater, connected directly to it on w-bus (k-line) with ThermoTest software and run tests. Surprisingly glow plug works fine, it glows till yellow-red color but every time I run test, o try to start heater with ThermoTest it writes fault: Glow plug / flame monitor interruption. What can be wrong with heater? Some say that it?s ECU faulty. But it?s visually clean, no corrosion and etc. Why glow plug glows, but starting with ThermoTest always fails with this error? Can it be because of some kind modification in ThermoTop ECU software and it allows to start only from cars internal system (temperature sensors or smth.)?

[HammiLam]

Is your circulation pump working well??? It also gives a lot of problems.

[baovit]

No, model ThermoTop Z does not have circulation pump at all. ThermoTop Z/C has.

[Timppasa]

Have you checked the glow plugs resistance. As the glow plug also monitors the flame, if resistance is wrong, the heater may think that there is no flame. I think resistance at 25 ?C should be 0.324...0.360 Ohm.

[baovit]

Yes, I have measured resistance and my cheap digital multimeter shows 0.7 Ohm. So I thought this must be a problem. But I also measured new glow plug resistance at spare parts shop and multimeter shows again 0.7 Ohm. So, maybe it's multimeters accuracy problem...

[tomtom0785]

Do you have a fault code stored like "Heater is locked" or "flameinterruption during work"??
I repaired a lot of heaters in Mazda 6 and MPV (all Webasto ThermoTop Z) - most of the times i only need to give a new burner (theres a "Stahlvlies" inside which is full of Diesel - most times this is totally burned down - so you wont have a good flame and the heater switches off)
try it!! ;-)
Sorry for my bad English

[baovit]

No, there's no such error "Heater is locked" or anything else abour instble flame or smth.
I read only B2449/B2450 "Glow plug circuit short to ground" from cars bus side and "Glow plug/flame monitor interuption" directly from heaters bus.
As it was mentioned before and according to repair manual - glow plug resistance should be 0.324Omh and I measure 0.7 Omh! But brand new glow plug resistance also 0.7 Omh for some reason and the same faults with it!! Is it possible that two glow plugs can be faulty...

Also I tried to run Combustion test with Mazda VCM/IDS, but I get the same faults.....

Winter is coming...:(

Maybe I should try to fix or replace ECU...

While you have repaired many of this type heaters, was it at least one time faulty ECU? :)

[tomtom0785]

with VCM/IDS you will always get the fault code "heater is locked" - this only means that something is wrong with it! you have to unlock first, then you can read out fault codes of heater - but not in quick test, you have to comm direct to heater!
"Flame monitor interruption" depends on the post i wrote before!Glow plugs are ok!
try to renew the burner unit - 90% of my not working heaters had this problem

[baovit]

Problem was solved by replacing ECU..Unfortunately did not succeeded to repair it...

[carclima]

this is nice unit you have on car.IF diag say glow faulty you need to check that resistance is below 1 ohm..never mind is it 0.3 or 0.8 as far as its below 1 all is ok with glow..it is temperature dependent..also in youre case glow plus is flame monitor as you maybe notice when heater is on glow plug is on power in pulses when there is no pulse for powe then monitoring work..so simple conclusion If you measure good resistance on glow plug cable and diag still tell that tis wrong...sory but change youre UCU..

when you dismantle unit from car its good time to check burner insert,IF you have a lot of white smoke in starting period change burner insert and work nice in next 500 hours..

regrads..

shit,,I start reply event dont read whole thread..of course you cant repair this ucu,,its tooo small and they use realy intrest chemicals for protection of parts