Community Forums

Buellah · 02-01-2023, 04:53 PM

Hello all.
My Heatpump will not heat. My coach has the mach15HP run by precision Plex. A/C mode works fine . Heat has not worked from the day I bought the coach 2 years ago . Long story. The current HP was installed a year ago. Another very long story. I understand that the equipment is under warranty. After being in the shop for 13 of the 21 months that I have owned the coach, That has not helped. Yet another long story. Now, I just want it to work and I don’t want to drive from Phoenix to Indiana to solve the problem.
Again
A/C mode works fine
Heat pump mode-fan runs but no heat. If I go into diagnostics mode on the PP Panel, and I put it in Heat mode, it cools. Seems the reversing valve isn’t activating. Ideas?

MrMark52 · 02-02-2023, 08:19 AM

Sounds like you’ve likely nailed it - reversing valve isn’t switching.

Easiest to just go to the root of the problem and measure power going to the reversing solenoid. Depending on how the unit was designed, the reversing valve coil will be powered in one mode, and unpowered in the other.

If it’s not doing that - then confirming the reversing valve control wire from the thermostat has been hooked up, starting at the thermostat and following thru to the unit.

Reversing valves can fool you - most have to be energized to go into A/C mode. If that is the case with yours, then why it’s always energized needs to be confirmed (control wiring issue).

Also - have you actually measured the discharge air temperature when the unit is in heat pump mode? 90 degree air will feel cool to the hand as well as drafty, but it is also providing heat to the space - although it may run 100% of the time.

hilgert · 02-02-2023, 08:40 AM

We had a similar problem with our Mach 15 heat pump. After a bit over 4 years of full timing, and almost constant use, the unit would cycle the compressor on/off very 30 seconds or so. In the end we replaced the unit, and I believe from the symptoms it was either the reversing valve or the freeze protection (I believe it was the latter).

MrMark52 is the right person for this...he helped immensely in diagnosing the issue.

Here is the link to my thread on this...in case it helps:

https://www.irv2.com/forums/f54/coleman-mach-15-issue-need-expert-advice-598914.html

Tskadberg · 02-02-2023, 09:40 AM

Do not buy Airxcel products. They do not honor their warranty. They drag the process out as long as they can asking you to jump through pointless hoops. I’m in it right now. There is a physical defect on my Mach 15. The dryer tank was mounted too close for the fan. My 30 year rv tech confirms this. After 2 months of back and forth they are demanding a “Cooling Performance” test. Which has zero to do with the defect. We can not do such a test during the winter as it requires a hot shop. Even if we could they have not said they will replace the unit. Just another hoop and then they will consider.

MrMark52 · 02-02-2023, 09:48 AM

Quote:

Originally Posted by Tskadberg

Do not buy Airxcel products. They do not honor their warranty. They drag the process out as long as they can asking you to jump through pointless hoops. I’m in it right now. There is a physical defect on my Mach 15. The dryer tank was mounted too close for the fan. My 30 year rv tech confirms this. After 2 months of back and forth they are demanding a “Cooling Performance” test. Which has zero to do with the defect. We can not do such a test during the winter as it requires a hot shop. Even if we could they have not said they will replace the unit. Just another hoop and then they will consider.

Just curious, and I saw this same post by you to someone else the other day - when you say “the dryer tank was mounted too close for the fan” - do you have a picture? I’m not sure I understand what your talking about (several things could be identified as a “drier”).

Thanks!

Buellah · 02-02-2023, 12:27 PM

I checked with a laser thermometer after different time periods up to an hour. Blows at ambient temp

Tskadberg · 02-03-2023, 05:13 AM

Quote:

Originally Posted by MrMark52

Just curious, and I saw this same post by you to someone else the other day - when you say “the dryer tank was mounted too close for the fan” - do you have a picture? I’m not sure I understand what your talking about (several things could be identified as a “drier”).

Thanks!

MrMark

Thanks for you interest. I had no clue until the rv tech told me.

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MrMark52 · 02-03-2023, 09:56 AM

Kind of hard to tell for certain, but I think what is being described as a drier is really a suction line accumulator - typical for rotary vane compressors such as used on MoHo units. They use the accumulator to insure all liquid is boiled off as the suction inlet to the actual compressor pump is tied directly to the pump valve port (the dome of the compressor is at high side pressure).

No real thermodynamic issues with the clearances shown. I see no damage to the one fan blade shown, so not real sure what the issue is there.

Do the prescribed checks on the reversing valve coil. I suspect it’s a 120vac coil - see if it has 120vac on it in heat pump mode. If it does, then with the unit running, carefully slide the coil off of the reversing valve. You’ll hear a big “sphewwww” and then the AC unit should switch function (from AC to Heat or Heat to AC).
If you don’t hear the “sphewwwww”, then either the coil is bad or the valve piston is stuck.

You can tap lightly on the valve to see if the piston will move - but too hard and you’ll dimple the cylinder the piston rides in and it will get stuck.

FWIW - the mass of air is so light that a laser thermometer won’t see it. What your probably reading is the temperature of the surface the laser light is falling on.

Tskadberg · 02-03-2023, 04:52 PM

Regarding the picture I posted of the “dryer” the issue is the dryer (smaller of the two tanks) makes contact with the fan blade causing the blade to explode. This happens when driving and we hit a bump. Has happened 4 times now. Didn’t mean to hijack the OP. Was just making the point that even with a clear cut manufacturing defect Colman aka Airxcel aka Thor does not honor their warranty.

MrMark52 · 02-03-2023, 06:54 PM

It is a tight clearance for certain.

The smaller tank isn’t a drier.

Confirm the correct fan blade is being used. See if a lessor pitch, smaller diameter can be found with 1 more blade (5 instead of 4 blades).

If one can’t be found, make sure motor mount hasn’t bent or shifted in some way.

While the positioning of a prop fan typically sits at 1/3 / 2/3 in the Venturi (and the one in the picture looks right), sliding the blade toward the coil a little more might provide more clearance - IF you can’t find a smaller diameter blade.

Tskadberg · 02-05-2023, 06:33 AM

Thanks the blade is certainly as forward as possible. I also zip tied the tanks down so they don’t bounce on their mount as much helped for sure but still lost a blade on a hidden speed bump on a off-ramp. I like the smaller blade idea. The “dyer” is attached to the larger tank and are mounted on vibration mounts so they have a lot of possible movement. I have two AC built like this.

CompuGuru · 02-07-2023, 04:10 PM

Buellah,
Looks like your post was inadvertantly hijacked!
about a year and a half ago, I had my front Mach-15 AC go bad and replaced it with a new Mach-15 with heat pump. Never could get the heat pump to work and finally found out that the original unit did NOT have a heat pump and the control board (that actually mounts in the AC unit) would not control the HP unit. Even though the panel shows heating, all it would do is blow out cool air. Fan running, but no heat.
Could this possibly be the problem that you are experiencing? If so, you will need to get a new control board that supports you AC/HP unit.