Webasto....

[Geoff]

Good luck.  I took my box apart and figured out how it worked and was even able to jump past the bad circuits to make it work-- that got me home but when I found a good used control box on eBay I bought it and everthing is well now.  I was able to take the box apart and identify the offending parts but I did not have ther resources to identify and order the replacement parts.  Maybe Sean would be willing to take our control boxes and fix them for us...

[opus]

I was trying to find pics of the insides but couldnt find any.  If I take this apart I will document it well.

[opus]

Nope, still same issue.

If I start the unit when all is cold, it will run as it should all day long.  If I drive for 6 hrs, park, turn it on while engine is still hot...to keep coolant hot so we can have heat for the night, it will run its short cycle [because the coolant is hot].  In just a couple minutes, it does its cool down cycle and that is it.  It wont start again until you flip the switch off and on.  Its not the photo eye, its not voltage, its not the temp sensor.  If it was the photo eye, it would try to restart but would shut down after a a little bit of trying.

Ideas?

[Sean]

...
If I start the unit when all is cold, it will run as it should all day long.

That part has me confused.  I'm not sure how starting from cold would be any different from starting hot...

If I drive for 6 hrs, park, turn it on while engine is still hot...to keep coolant hot so we can have heat for the night, it will run its short cycle [because the coolant is hot].

And that part does not make sense, unless the unit is miswired.  If the coolant is already hot (>165°F), then the unit should not fire at all.  The control thermostat should not be calling for it to fire.  If your engine and hydronic systems are separated by a heat exchanger, though, it is possible that the hydronic coolant is cooler than the cut-in temperature of the control thermostat, in which case it would cycle on, but it should run a full cycle (about the same cycle time as when it is normal operation but already up to operating temperature, as opposed to the much longer cycle from a cold start).

In just a couple minutes, it does its cool down cycle and that is it.  It wont start again until you flip the switch off and on.  Its not the photo eye, its not voltage, its not the temp sensor.  If it was the photo eye, it would try to restart but would shut down after a a little bit of trying.

That last statement is not correct.  If the flame sensor (photo eye) ever shuts the unit down at any time, the unit will not re-fire until it has been power cycled.  I wrote this in my first post here, and then you wrote that Webasto also told you the same thing:

Webasto says ... if it was the flame eye, it wouldnt restart again.

If the flame sensor is perfectly clean, and all the wires are tight, you should test it with an ohmmeter.  The specs for what you should read under various conditions are listed in the service manual.

If it is not the flame sensor, it is most likely the control box.  Sticky relays can be hard to troubleshoot because they are often intermittent.  If you could borrow a working control box for testing, that might narrow it down.

-Sean
http://OurOdyssey.BlogSpot.com

[David Anderson]

Interesting,  Sean describes closely what mine was doing in Cloudcroft that I wrote about in the other thread.  However, I could not duplicate it again when I got back home after the trip.  I probably need to crack it open and give it a thorough cleaning.

David

[opus]

That part has me confused.  I'm not sure how starting from cold would be any different from starting hot...

Exactly, thats what I thought.

If I drive for 6 hrs, park, turn it on while engine is still hot...to keep coolant hot so we can have heat for the night, it will run its short cycle [because the coolant is hot].

And that part does not make sense, unless the unit is miswired.  If the coolant is already hot (>165°F), then the unit should not fire at all.  The control thermostat should not be calling for it to fire.  If your engine and hydronic systems are separated by a heat exchanger, though, it is possible that the hydronic coolant is cooler than the cut-in temperature of the control thermostat, in which case it would cycle on, but it should run a full cycle (about the same cycle time as when it is normal operation but already up to operating temperature, as opposed to the much longer cycle from a cold start).

The unit is not miswired and according to Webasto, the ohm details I gave them are correct. I do think there is a heat exchanger involved.  When it does fire with warm coolant, it runs a short cycle then runs a cool down cycle.

In just a couple minutes, it does its cool down cycle and that is it.  It wont start again until you flip the switch off and on.  Its not the photo eye, its not voltage, its not the temp sensor.  If it was the photo eye, it would try to restart but would shut down after a a little bit of trying.

That last statement is not correct.  If the flame sensor (photo eye) ever shuts the unit down at any time, the unit will not re-fire until it has been power cycled.  I wrote this in my first post here, and then you wrote that Webasto also told you the same thing:
Webasto says ... if it was the flame eye, it wouldnt restart again.

The eye was dirty.  I meant it wasnt a bad photo eye.  You are saying it wouldnt try to restart itself without a power cycle...ok, got it.  But if the eye was dirty, why would it fire again after I power cycled it?  And again, why would it run all day long if I started it from a cold state?

If the flame sensor is perfectly clean, and all the wires are tight, you should test it with an ohmmeter.  The specs for what you should read under various conditions are listed in the service manual.

If it is not the flame sensor, it is most likely the control box.  Sticky relays can be hard to troubleshoot because they are often intermittent.  If you could borrow a working control box for testing, that might narrow it down.

The whole issue is that it does it when the coolant has gone above the shutoff temp for the unit.  If I only used it as a starting aid on a cold engine, I would never have noticed this issue.

[Geoff]

Again-- its either the control module or loose connections/plugs at the module.  I have spent countless hours playing with the system and diagnosing this and that and a new control bosx fixed my same problem.

[opus]

Ugh, thats what I am thinking too.

[Sean]

...
The eye was dirty.  I meant it wasnt a bad photo eye.  You are saying it wouldnt try to restart itself without a power cycle...ok, got it.  But if the eye was dirty, why would it fire again after I power cycled it?

Well, I can tell you from experience that a partially obscured flame sensor *will* allow the unit to run, intermittently.  Unless it is obstructed completely, a dirty sensor will have a varying resistance while the unit is running, dependent on many factors including the actual brightness of the flame, the vortex in the combustion chamber, and possibly the phase of the moon.  At some point, the resistance will indicate to the control box that the flame has gone out, even though it hasn't.  The unit will then cool down, shut down, and remain off until power cycled.  Power cycling allows the whole process to start all over again.

Again, this is from direct experience, not theory.

And again, why would it run all day long if I started it from a cold state?

That's the part I am having trouble understanding.  But without seeing a complete wiring diagram of your system, it's hard to diagnose remotely.

Do you have such a diagram?

-Sean
http://OurOdyssey.BlogSpot.com

[Geoff]

Sean--

If I send you my broken control module could you diagnose/fix it for me?  You say they are quite simple.  I would be quite happy to pay you for your services.

--Geoff

[opus]

The eye was dirty enough with a black film over it that I used carb cleaner on it and not just a rag.  My wiring diagram is exactly what is in the manual.  Webasto asked me a bunch of questions and had me verify wiring, and he was pleased with my answers.  I guess give me an idea where you are going and I might be able to answer better.

[Sean]

If I send you my broken control module could you diagnose/fix it for me?  You say they are quite simple.  I would be quite happy to pay you for your services.

OK, so "quite simple" is perhaps an overstatement.  What I meant was that there's not anything overly sophisticated in there -- it's really just a bunch of low-tech relays and a couple of discreet components that steer some signals around.  Webasto likes to pretend it's some kind of magic electronic device, especially when they are billing you for one.

If we happened to cross paths someplace, I would be more than happy to help you diagnose and repair your control module.  My experience is that the vast majority of problems are due to sticky relays, and often can be cured either by spraying contact cleaner in them, or else by carefully prying off the dust cap and cleaning them up with some emery.  Diagnosis involves a lot of patience while waiting for the symptoms to develop as you probe each relay input and output with a voltmeter.

The relays themselves can also be replaced, but it requires some de-soldering skill, and matching these little weird relays up in a catalog can be daunting.

I'm sorry to say that I don't have the test bench I would need in order to diagnose or repair your box without your burner unit as well.  I was forced to learn about these units by troubleshooting my own, which of course was attached to my boiler at the time and is a bear to access.  I'm sorry that I did not have the presence of mind, in the heat of battle, to take photos of the process, which would have helped several folks here.  My unit is also 24v, so I could not, for example, swap your box into my setup for testing even if it were easy to do so.

There are a handful of folks in the business of refurbishing these boxes -- it sounds like that's where you acquired your replacement.  You might check with some of them to see what they charge to diagnose and repair one, or else they might simply give you a credit for your box as a "core" towards a refurbished one, if you are looking for a spare.

-Sean
http://OurOdyssey.BlogSpot.com

[Geoff]

Good to know.  I will take it apart this week if it dries off some.  I have heard plenty about the control boxes.  If need be I would take it apart and repair it, with the help of a local guy.  You think someone would have come up with a workaround for the expensive control box.

So, Opus, you make any headway on repairing your control module?  Sean politely bowed out so the only guy I know that will rebuild them is the guy on eBay that wants $420 with a $100 core deposit.

--Geoff

[opus]

Webasto doesnt think its the box.  They are thinking it is the green/green overheat thingy.  He thinks when the engine is hot, and I turn it on, it is bouncing close to overheat.  I dont because the engine never gets over 180.  Unless of course, it is defective.  We're on the road this weekend, I will try it and see what happens.