A few questions... and comments.

[David T. Richelderfer]

On our recent trip to Astoria the diesel burner would not ignite.  I pulled off the Aqua Hot covers and pulled the fuses.  The 2nd fuse from the left was blown.  The fuse in place was blue, not red as shown in the online manual.  After replacing the fuse with blue, the diesel burner's blower fan tried to start but it did not run over about 3 seconds.  The burner actually did not have time to light before it shut down.  The new fuse did not blow.
      1. The diesel burner has worked flawlessly since our purchase of the coach in August 2012.  What condition what cause the fuse to blow?  Is it time for a technician to give it a look?
      2. I called Orman on the phone (thank you for taking my call) and posed the problem to him... the problem being that the diesel burner would not start AFTER replacing the blown fuse.  After trying several things, we determined that the "low temperature thermostat" must be satisfied due to the electric hydronic heating element having the water plenty hot already.  So we turned off the electric hydronic heating element and ran the hot water down until it cooled substantially.  The diesel burner started up at this point.  Orman surmised the "low temperature thermostat/s" may be getting weak and requiring replacement.  Any other thoughts?  Again, is it time for a technician to give it a look?
      3. After shutting off the diesel burner I read the exhaust clearing and cooling blower fan should operate for several minutes.  In the past this blower fan had always operated smoothly before it shut down after several mninutes.  This time it ran smoothly for several minutes and then would cycle through a run-stop routine.  It would run for a few seconds (5 seconds), then try to stop for about 1 or 2 seconds.  The blower fan repeated this cycling 5 seconds on, 1 second off about 20 or 30 times, and finally shut down completely.  I do not remember this happening in the past .  I think I am (or have by now) talked myself into having a technician take a look.   lol

On the drive home from Astoria on Wednesday, I noticed my transmission temperature was increasing.  Prior to this Astoria trip I had never seen the transmission temperature above 107 F... usually it runs at 104 F.  After leaving Portland heading East, the transmission temperature had slowly raised to 124 F upon getting to The Dalles (85 miles from Portland).  I stopped there for about 15 minutes to watch the temperature while allowing the engine to idle.  The transmission temperature rather rapidly decreased to under 110 F.  I proceeded on East, and the temperature increased back to 124 F and higher... all the way up to 134 F by the time I was East of Arlington (50 miles East of The Dalles).  Wednesday was a pretty hot day in Eastern Oregon... probably 30 to 35 degrees warmer than at Astoria when I departed at 9:30 am.
        1. What temperature should my transmission run?
        2. In the coach sale details, the prior owner stated "Additional radiator for transmission for extreme temperatures."  I called a friend who has a Beaver Monterey and asked what his transmission temperature usually runs.  He stated, "I'm not sure, but I think near 200 F."  Should I have a technician look at my transmission?

And I thank you in advance for your time and interest.

[Marty and Suzie Schenck]

Can't say what to do about your Hydro-Hot but my Thunder's trans temp usually runs 5 degrees plus or minus as the water temp. 194 degrees.
Marty

[Bill Sprague]

David,

My transmission always runs significantly cooler than the engine.  The Aladdin says the engine is usually around 185 and the Allison about 160.  Mine is a Cummins so the radiator and cooler installation may be different.  On many, the transmission cooler is inside the radiator with the idea that the engine heat will help warm up the transmission fluid for smoother operation.  Others have the transmission cooler outside the radiator. 

As per Orman's suggestion, I have replaced the high temp thermostat.  In my case, it was thoroughly melted and had completely failed.  It is not a difficult replacement job.

I have a love hate relationship with the HydroHot.  When it works I love it.  When it acts funny I hate it.  My guess from your description reminds me of a problem I had several years ago.  One of the relays inside the $900 Webasto computer box was sticking.  The box is the the one about the size of two card decks that is attached to the burner.  It has two wire bundles plugged into it.  The HydroHot computer and the Webasto computer talk to each other and make the various parts start and stop. 

Mine was intermittent.  When it didn't work, a slight tap with a screwdriver handle would unstick it.  The hard part was the official troubleshooting.  It would not stick in the shop.  I finally had to beg the shop to park a tech next to it at $90 per hour to wait for it to malfunction.  When it finally did, he identified the issue and ordered a box. 

My suggestion is to try tapping the box the next time it does not do what it is supposed to do. If that corrects the situation, you may be in line for the next $900 box. 

[Edward Buker]

David,

All of the burner controls and timings are provided by the silver metal box on the burner as Bill indicated. It is idiotic in this day and age to use mechanical spring relays with contacts in a heating and cooling environment but it is an old design and Webasto seems to have no reason to stop selling us expensive boxes that fail. These are classic symptoms of aged springs on the relays and they are not replacable from my search. I have replaced my control unit also. You can search the web and there are suppliers out there that will cost less than the $900 and you can save a service call given this is just a set of plugs that have to be removed and then plugged into the new unit.

Later Ed

[David T. Richelderfer]

From Bill's and Edward's explanations, I am guessing my Aqua Hot's Webasto brain box may be ailing... and will at some most inopportune time take its last breath.  I best start looking for a replacement and have it on hand.

Thanks guys...  DTR

[Edward Buker]

David,

You may get to the point at times, as the controller ages, where the burner will shut down, but the blower just keeps running rather than being intermittent. You will have to break the 12V feed to unlatch the controller relay that operates the blower in the silver box if that occurs. You can do that by shutting down the inverter/charger first and then shutting off the house battery switch in the battery bay for 10 seconds or so. Turn it back on and then turn the charger back on.....pain in the butt in the middle of the night.....been there.

Later Ed