2018 Greyhawk 29MV heat pump does not start

[watchout]

I recently bought a lightly used 2018 Greyhawk 29MV. Love the layout and everything works perfectly, except... the heat pump (Mach 15 with AirXcel digital thermostat) will not come on at all. It is not the thermostat setpoint, I've ensured it within 5F of the coach temperature.

So, I pulled the tstat off the wall and it appears there is no connection to the heat pump call for heat terminal (labelled WHP). Also looked at the control box in Mach 15 unit and there is no connection to the "W" terminal which is the corresponding heat pump control terminal. It's not that it is just disconnected, it looks like they never ran a wire from the tstat to the unit. It is only a 4C cable coming into the unit and it needs to be 5C.

Any other 2018 29MV owners have a heat pump that won't start?
Thanks,

[Sundancer330]

Are you sure your model has a heat pump, some models only have the optional heat strip.

[watchout]

There is no heater installed, I can see where it would be installed and there is nothing there. I haven't contacted Jayco yet to find out what this VIN is really supposed to have.

[Grumpy]

Originally Posted by watchout

I recently bought a lightly used 2018 Greyhawk 29MV. Love the layout and everything works perfectly, except... the heat pump (Mach 15 with AirXcel digital thermostat) will not come on at all. It is not the thermostat setpoint, I've ensured it within 5F of the coach temperature.

Do you have 1 or 2 a/c's? If 2, you only have 11,000's and no HP. Obviously it's been that way since it was originally sold.

[Sundancer330]

If you dont have the optional heat strip you need one of these.
https://www.rvupgradestore.com/Coloe...yABEgKsCPD_BwE

[watchout]

Originally Posted by Grumpy

Do you have 1 or 2 a/c's? If 2, you only have 11,000's and no HP. Obviously it's been that way since it was originally sold.

Only 1 a/c. It is definitely a 15k unit.

[watchout]

Originally Posted by Sundancer330

If you dont have the optional heat strip you need one of these.
https://www.rvupgradestore.com/Coloe...yABEgKsCPD_BwE

But even if I install a heat strip, there is no connection between the tstat and the control unit, so the strip would never energize. Correct ?

[Grumpy]

Originally Posted by watchout

Only 1 a/c. It is definitely a 15k unit.

Originally Posted by watchout

But even if I install a heat strip, there is no connection between the tstat and the control unit, so the strip would never energize. Correct ?

Yes you need 5 wires. High fan, low fan, a/c, heat and 12v ground. Is the white wire still in the bundle, but cut short?

The control box would have a socket for the optional heat strip to plug into if it is a Heat Pump. Heat pumps are already designed for the Heat Strip option to be added, but many manufacturers don't include them. The control box is designed for the Heat Strip to kick in after the Heat Pump shuts off if the outside temp is below 40.

[watchout]

Originally Posted by Grumpy

Yes you need 5 wires. High fan, low fan, a/c, heat and 12v ground. Is the white wire still in the bundle, but cut short?

The control box would have a socket for the optional heat strip to plug into if it is a Heat Pump. Heat pumps are already designed for the Heat Strip option to be added, but many manufacturers don't include them. The control box is designed for the Heat Strip to kick in after the Heat Pump shuts off if the outside temp is below 40.

I haven't dug into the bundle yet, but that was the next step. Interestingly, the color code of the wires at the control box is not identical to what is at the tstat. In particular, the compressor wire is yellow at the tstat, but it is red at the control box. So, must be a splice to a different cable at some point. But that wouldn't explain why there is no W wire at the tstat end. Will be a pain to try to dig into the mass of wires behind the wall...

Yes, the control box has the socket for the heat strip, but its not used (because there is no heat strip installed ) I've got an email into Jayco to see what they say should really be there. Not counting on a lot of info from them.

[Grumpy]

Originally Posted by watchout

I haven't dug into the bundle yet, but that was the next step. Interestingly, the color code of the wires at the control box is not identical to what is at the tstat. In particular, the compressor wire is yellow at the tstat, but it is red at the control box. So, must be a splice to a different cable at some point. But that wouldn't explain why there is no W wire at the tstat end. Will be a pain to try to dig into the mass of wires behind the wall...

Yes, the control box has the socket for the heat strip, but its not used (because there is no heat strip installed ) I've got an email into Jayco to see what they say should really be there. Not counting on a lot of info from them.

If you pull the wires out of the wall behind the thermostat you probably will find that the colors going to the a/c match the control box. Normally the T-stat wires are connected to the 5 pair with wire nuts and pushed into the wall there may be a fuse in the wall bundle as well. As I said, JAYCO does not include the Heat Strip, but it is a simple add once you get the wiring figured out. I added it to our PINNACLE and even added them to our regular a/c units without Heat Pumps, only then I had to run an extra wire and change the control box too.

[watchout]

Originally Posted by Grumpy

If you pull the wires out of the wall behind the thermostat you probably will find that the colors going to the a/c match the control box. Normally the T-stat wires are connected to the 5 pair with wire nuts and pushed into the wall there may be a fuse in the wall bundle as well. As I said, JAYCO does not include the Heat Strip, but it is a simple add once you get the wiring figured out. I added it to our PINNACLE and even added them to our regular a/c units without Heat Pumps, only then I had to run an extra wire and change the control box too.

Grumpy, thanks for the input. I'll do some inspection later this week and see if I can sort the wiring out. Should be fun getting the rats nest of wires through that hole in the wall

If I can get the wiring solved, the the strip heater sounds like an easy upgrade.

[Grumpy]

Originally Posted by watchout

If I can get the wiring solved, the the strip heater sounds like an easy upgrade.

Yep, plug & play..