Author Topic: Hydro hot not igniting.  (Read 7313 times)

Tom Fisher

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Hydro hot not igniting.
« on: July 30, 2015, 03:18:17 PM »
I pulled  into camp ground late after noon, set up and pushed to diesel switch for the hydro. Next morning I could hear the hydro running but did.t sound right. Went out and looked at the exhaust pipe, and there was diesel dripping out of it and according to the large area of saturation, it appears it had run all night. I shut switch off, and did not turn back on due to all the diesel I think is in the unit. Can I try to get it to ignite again, or do I have to tear apart. I had this unit serviced 3 times last summer, with the last one appearing to me to be the only one that knew what he was doing. RV medic out of casa grande.
Thanks, Tom

Stan Simpson

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Re: Hydro hot not igniting.
« Reply #1 on: July 30, 2015, 03:30:02 PM »
We had that issue. Turned out to be a thermostat that is inside the unit. It took our tech about 35 minutes to put in a new one, and we were good to go.
Stan Simpson & Becky Glover & Moe the cat
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Al Lewis

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Re: Hydro hot not igniting.
« Reply #2 on: July 30, 2015, 05:09:21 PM »
I have had a similar issue. When I did get it to ignite it did not explode but did smoke heavily for about ten minutes. On mine the problem occurred at cold start up (less than 50 degrees). The work around was to run the electric heat until water was warm then the diesel would fire. If you call the hydro hot people they will say to do the nozzle and filter change but that has never fixed anything for me. I am sure that is the first thing your tech has done. The next thing to look at is the flame sensor. I changed mine but it did not help. A hair drier on the control board makes it work so I conclude I have something temperature sensitive on the burner control board. Parts are not cheap so I am dealing with the problem for now. If you are inclined to work on it yourself I can help. I found a source for parts at about 30 percent less than hydro hot.

Al Lewis

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Re: Hydro hot not igniting.
« Reply #3 on: July 30, 2015, 07:06:22 PM »
I failed to mention some of the testing I did before going to the flame sensor. You must verify the igniter is firing. The electrodes must be clean and properly spaced. There is a tool provided to check the space. The igniter coil can be dismounted. It should fire when power is reconnected.

Les Brandt

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Re: Hydro hot not igniting.
« Reply #4 on: July 31, 2015, 03:24:21 PM »
I found a source for parts at about 30 percent less than hydro hot.

Al, can you please post your source link?

Al Lewis

  • Guest
Re: Hydro hot not igniting.
« Reply #5 on: July 31, 2015, 05:44:07 PM »
The best source I found for the Webasto diesel burner unit is Sure Marine Service out of Seattle.  They have a good web site if you put www in front of their name and .com after.  A phone number is 206-784-9903.  To work on the hydro hot you need to download the shop manual from the Aqua Hot heating systems people.  It is very good and has part numbers.  If you google the part numbers you will find sources such as Sure Marine.  Parts outside the burner assembly probably have to come from Hydro hot.  The fuel filter can be found through an auto parts store.

Frank Towle

  • Guest
Re: Hydro hot not igniting.
« Reply #6 on: August 01, 2015, 07:20:34 PM »
14 year old Hydro-hot or any electrical device can have corrosion (rust) preventing good wire contact causing resistance to increase and voltage to drop. 

Shine up any wire connections, use a di-electric on those connections, measure voltage everywhere you can - even 1/2 volt drop should be avoided.

Follow the hydro-hot service manual step by step, use a little common sense and you will locate the offending connection. 

I believe the Hydro-hot system as designed and built is almost bullet proof and will last a lifetime.  Corrosion can not be avoided. That's why bridges and towers are periodically scraped and painted.  Many 'fixes' of replacing circuit boards are a convenience to the service person at the expense of the service-ee.  Look for grey solder points on circuit boards - that's corrosion.  Just reflow the solder but not with a blow-torch  ;D

Also... components can fail especially wire-wound transformers like the one creating the spark for ignition.  Many times still caused by overheating from increased resistance (see above) melting insulation.  If transformer or other heat sensitive component has to be replaced make sure the underlying cause is also corrected.