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Old 01-08-2011, 02:54 PM   #1
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Hydro-Hot "Low Fluid" Issue

We've had our coach in storage in Borrego Springs for a few weeks while we were north for the Holidays. On returning, the HH would not work at all. Checked the unit and saw a red fault light ("Low Fluid"). I'd been noticing over the past few months that the overflow container seemed to be going down -- and when it was "cool" was almost empty. After we returned I noted the overflow container was in fact completely empty at this point. Managed to get the right PG fluid here in Borrego Springs, and I assumed I should add fluid to the main tank by removing the radiator cap. However, before I'd even added a cup it was overflowing. So cleaned up a bit of spillage, and tried adding some to the overflow container. That caused more spillage on top of the tank, so we gave up on that idea, screwed the radiator cap back on, and manually filled the overflow tank to the "cool" mark. The manual says once the fluid is replaced the red fault light will go off. Nope. It's still on, and we're still not able to use the HH unit. Wondering if anyone else might have been there/done that.


2007 34' FDDS Ltd SE
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Old 01-08-2011, 05:50 PM   #2
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I would suspect a bad float switch or connection. A quick look at the wiring drawing indicates the switch should be closed when the antifreeze is at the required level. Check to see if you have continuity at the switch wires. You could short the switch temporarily and see if the unit will reset. Don't run it long without fixing the cause.

Wayne & Kathy
05 Alpine 40FDQS #75330 Towing 24' car hauler, 2012 Spyder, 2003 Harley FatBoy
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Old 01-08-2011, 10:27 PM   #3
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The float switch has gone south maybe, but you have a leak someplace as well. First place to look is the hose from the overflow tank to the top of the unit. Make sure that hose is not leaking along its length or at either end-little clamp tight?. Next if you can reach behind the unit and feel to see if any coolant is leaking on those lines at the rear of the unit (make sure it's cold and not running). If not leaking at any visible place, then check all the points where those lines run to the cozy III heat exchangers, then look for puddles of red stuff all over the coach. Its smell can be a way to find them as well. If no leaks detected (Should not lose fluid over time-so there has got to be a leak), then send me a pm with your cell number, I will call you and describe to you how to short the float switch at the control board. But make sure the BF (boiler fluid) is full by removing the radiator cap first, if it is, replace the cap, and then we are good to go. Oh it could also be a bad cap, as HH recommends replacing them every two years. I keep my old one for a spare in case something happens to the new one. I would like the model number as well so I can look up the correct control board diagrams for your unit.
Monty & Janet - 2007 Alpine APEX 40 MDTS
S/N - 75715 - Retired - Master Certified RV Tech
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Old 01-12-2011, 01:33 PM   #4
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Thanks for the replies. It does appear to be the float switch, and as Monty has suggested there is a work-around for it, a copy of which I've been able to obtain. However with a bona fide and highly recommended Hydro-Hot tech now located, we'll opt to make sure it gets done correctly, trading off an added 48 hours of cold water for the opportunity to avoid having me do something unexpected. Tom
2007 34' FDDS Ltd SE
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Old 01-18-2011, 10:12 PM   #5
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We just had our second float switch replaced. The first was two years ago, and might have been the plastic model, part# ELX-01G-ML7 ~$128. The brass one is part# ELE-800-002 ~$152. AquaHot now has a pressure sensor third model, ELE-200-001-FRU ~$270 that they are using. Ron Domoe of Sierra Mobile RV, out of Minden NV south of Reno, has been very helpful with our unit. He told me how to bypass the switch with a jumper across pins 15 & 16 of the upper right connector. I unplugged the spade connectors of the switch and inserted a blade type fuse until we could get it replaced. We didn't go with the new one as AquaHot hadn't convinced him that the new one had no problems.
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Old 01-25-2011, 08:44 PM   #6
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HI Tom
I just read your post regarding your Coolant level light,
As posted above you must be absolutely positive that your cooland level is up. Then you can by-pass the switch, If you would like to contact me directly, I may be abe to help you, Oh yeah, I am a factory trained and certified service tech.
Orman Claxton
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