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PBK Images · 02-04-2023, 11:34 AM

Can't find exact symptoms so starting a new thread. HYDRO-HOT unit will not ignite. Based on the following, maybe someone has a clue....*Just serviced unit with fuel *nozzle and cleaning. (Fuel filter previously changed) Did NOT test just before service but it ran well about three weeks prior. PROBLEM: Unit will not ignite. INDICATIONS: Initiate start sequence by turning on*Diesel*rocker switch. The Green light by*diesel switch comes ON, blower starts. No ignition. No smell of diesel fuel from*exhaust . Control panel shows no red lights but shows Green LED's in Diesel Burner Status, Pump #3, and Heating status. After about 20 to 25 seconds, green light by interior rocker switch *turns off. All the illuminated LED's go OFF on control panel -- blower runs for another 2.to 3 minutes, and cuts off. New diesel fuel. NOTE: Seems control*panel and*diesel switch lites*go OFF *at the same time that there should be ignition and fuel started.*This unit does NOT have a safety switch on the cover. The red light *indicating low*coolant warning is NOT on. Fuel tank is full. Thanks for any advice. Probably something to do with the normal removal and re-installing the burner motor assembly but I don't know what. All wires inspected and seem normal. Flame sensor appeared clean.

96 Wideglide · 02-04-2023, 11:55 AM

Did you clean and check the gap on the igniter rods?

PBK Images · 02-04-2023, 12:59 PM

Yes, indeed. Thanks for checking.

groveln · 02-04-2023, 02:17 PM

I had this issue & worked on it by realigning & swapping out the nozzle to no avail..2 days on it & finally found the problem. There's that photocell that must see the nozzle spay & if it's dirty from built up fuel residue & crap it won't allow the ignition process to continue. I wiped it clean & it fired up as it should..so check that.

PBK Images · 02-04-2023, 03:04 PM

Quote:

Originally Posted by groveln

I had this issue & worked on it by realigning & swapping out the nozzle to no avail..2 days on it & finally found the problem. There's that photocell that must see the nozzle spay & if it's dirty from built up fuel residue & crap it won't allow the ignition process to continue. I wiped it clean & it fired up as it should..so check that.

We did clean off the photocell that exists to detect flame after ignition. When it does, it then shuts off the ignitors but not the fuel. However, it is possible that the flame detector may be bad. If that happens it MAY prevent both fuel and ignition from starting depending on how the control box is programmed. Does anyone know? When you had your issue did the green light by the Diesel switch stay on or go OFF. Thank you.

bentjm · 02-04-2023, 08:23 PM

The troubleshooting procedures are well documented in the manuals for the various Hydrohot models.

Download the manual and follow the procedures.

It is easy to ohm out the photo cell.

I chased an intermittent no start problem for over a year. I went through all of the troubleshooting procedures. It was ultimately the coil. I had suspected it for months but it is ridiculously expensive. I finally paid the $400 for a new coil and have had no problems since. The old coil had a broken lead wire down inside the potting material. If you positioned the lead just right, it would work - until the vibrations from driving down the road moved it.

Download the manual and follow the troubleshooting procedures and you will figure it out.

PBK Images · 02-05-2023, 08:48 AM

Quote:

Originally Posted by bentjm

The troubleshooting procedures are well documented in the manuals for the various Hydrohot models.

Download the manual and follow the procedures.

It is easy to ohm out the photo cell.

I chased an intermittent no start problem for over a year. I went through all of the troubleshooting procedures. It was ultimately the coil. I had suspected it for months but it is ridiculously expensive. I finally paid the $400 for a new coil and have had no problems since. The old coil had a broken lead wire down inside the potting material. If you positioned the lead just right, it would work - until the vibrations from driving down the road moved it.

Download the manual and follow the troubleshooting procedures and you will figure it out.

Thanks--I researched that last night--great manual. The most likely culprit is the VDC hi limit thermostat. Manual refers to a red reset button. Now trying to locate that. Did you test that during your diagnosis?

bentjm · 02-05-2023, 05:14 PM

Quote:

Originally Posted by PBK Images

Thanks--I researched that last night--great manual. The most likely culprit is the VDC hi limit thermostat. Manual refers to a red reset button. Now trying to locate that. Did you test that during your diagnosis?

My unit had several problems - mostly due to lack of use.

I did all the initial things like new filter, nozzle, good cleaning of the combustion chamber, ...

I also had to replace the relay on the AC side and one of the thermostats - I don't recall which one.

PBK Images · 02-05-2023, 05:31 PM

Quote:

Originally Posted by bentjm

My unit had several problems - mostly due to lack of use.

I did all the initial things like new filter, nozzle, good cleaning of the combustion chamber, ...

I also had to replace the relay on the AC side and one of the thermostats - I don't recall which one.

Always something... based on using the troubleshooting flow chart, I think my issue is a bad controller that will not process the hi limit thermostat information. (I was able to check the thermostat and it is OK.) Burt if the controller thinks the thermostat is showing an out of range temp, it will not allow the fuel pump to start or the ignitors to spark. Hence, no start, no smell of fuel (which would likely occur if the flame detector were bad.)

bentjm · 02-06-2023, 07:56 AM

Quote:

Originally Posted by PBK Images

Always something... based on using the troubleshooting flow chart, I think my issue is a bad controller that will not process the hi limit thermostat information. (I was able to check the thermostat and it is OK.) Burt if the controller thinks the thermostat is showing an out of range temp, it will not allow the fuel pump to start or the ignitors to spark. Hence, no start, no smell of fuel (which would likely occur if the flame detector were bad.)

The guys that work on these things for a living have a standalone controller that they use to bypass all that stuff and force the various parts to work.

Might be worth it to get one of them to take a look before paying for a new controller.

Good luck.

**Spdracr39** · 02-06-2023, 09:01 AM

Quote:

Originally Posted by PBK Images

We did clean off the photocell that exists to detect flame after ignition. When it does, it then shuts off the ignitors but not the fuel. However, it is possible that the flame detector may be bad. If that happens it MAY prevent both fuel and ignition from starting depending on how the control box is programmed. Does anyone know? When you had your issue did the green light by the Diesel switch stay on or go OFF. Thank you.

My flame detector went bad with the same symptoms. It killed the spark but not the fuel spray. As mentioned Ohm testing it is easy and replacement took care of it.

PBK Images · 02-06-2023, 09:28 AM

Quote:

Originally Posted by bentjm

The guys that work on these things for a living have a standalone controller that they use to bypass all that stuff and force the various parts to work.

Might be worth it to get one of them to take a look before paying for a new controller.

Good luck.

Not a bad idea to have one although in this case I did a complete check of the part of the controller that is connected to the DC hi-limit thermostat. These procedures are laid out in the shop manual. The stand alone controller you reference would be nice to have as you don't need an assistant to go inside and turn ON/OFF the main Diesel switch. The cost between $170 to $270 on e-Bay.

PBK Images · 02-06-2023, 09:29 AM

Quote:

Originally Posted by Spdracr39

My flame detector went bad with the same symptoms. It killed the spark but not the fuel spray. As mentioned Ohm testing it is easy and replacement took care of it.

In my case there is no fuel and no spark so it is not the flame detector photo-cell. Thanks.

American Eagle · 04-12-2023, 06:50 AM

Did you get the system to fire up? I have the same non fire. I did the yearly service on the coach with new filter filled the filter with clean fuel. When it came to start nothing and it would do the three minute clean out. I put the old nozzle in and nothing. Finally I told the burner out and put the new nozzle back and adjusted the coil leads and brought them closer to the nozzle with the setting tool and it started up fine.