Another Heatpump Question

mikf · 05-17-2016, 11:01 AM

I have a 2002 adventure 35u with a model 6535a871 heat pump with 6535-3209 pc board. and Coleman-MachTrue air thermostat. With the thermostat position to electric the heat pump comes on and with the 1st compressor I read 12 amps and when the 2nd. one kicks in it settles back to 17. Which seems to low from what I read when I search this forum. There is about a 4 degree rise in temp. when I measure at the in-take and the first exhaust in the ceiling. I am not sure if that is enough. No matter how high I set the thermostat it never turns on the gas heat unless I select gas heat. The manual says once you select electric heat the PC board takes over and controls the heat pump, BUT does the thermostat control when it turns on the gas heat and shuts down the heat pump, or is it still the PC board? I am thinking I should replace the thermostat, but am looking for a second opinion. Thanks

DancinCampers · 05-18-2016, 07:20 AM

The start up of both compressors and fan motors are controlled by the pc board, once the tstat sends the signal to the board. Both compressors are used in electric heat mode.

Tstat controls stopping unit operation, activating gas furnace if heat pump can't keep up to set temp, and locking out unit, and shutting off unit due to freezing coils.

You seem to have 2 separate issues, first the operation of 2nd compressor, second the initiating of gas furnace if temp is set several degrees above room temp.

If both compressors operate in cooling mode, then it may be an issue with the pc board.

It would appear to be a tstat issue regarding the gas furnace operation.

pasdad1 · 05-18-2016, 07:39 AM

Quote:

Originally Posted by mikf

?....There is about a 4 degree rise in temp. when I measure at the in-take and the first exhaust in the ceiling. I am not sure if that is enough.

If outside air temperature is above 45F then 4 degree difference is not enough. Should be able to produce at least 15 degree difference between air intake and exhaust.

mikf · 05-18-2016, 08:23 AM

Quote:

Originally Posted by pasdad1

If outside air temperature is above 45F then 4 degree difference is not enough. Should be able to produce at least 15 degree difference between air intake and exhaust.

I did not think that was enough. And I suspect it has something to do with it not drawing enough amperage. Since it is 14 years old I am thinking it may not be worth putting to much money in it. I wonder if the new ones are better.

pasdad1 · 05-18-2016, 08:47 AM

Quote:

Originally Posted by mikf

I did not think that was enough. And I suspect it has something to do with it not drawing enough amperage. Since it is 14 years old I am thinking it may not be worth putting to much money in it. I wonder if the new ones are better.

How does it work in cooling mode?

DancinCampers · 05-18-2016, 11:09 AM

Also, check you outside vertical ductwork for leaks.

If you turn off the circuit breaker for the #2 compressor, you can heat with the #1.

mikf · 05-18-2016, 03:54 PM

Quote:

Originally Posted by pasdad1

How does it work in cooling mode?

I noticed the heat pump not heating last fall and thought the AC was OK. it kept us cool last month in FL. with the temp in the low 80's, but the amps always stayed low around 18. Today the temp out side was about 60. I turned the thermostat down to 40 and after 1/2 hour had a 12 degree drop from intake to exhaust. Then I turned number 2 compreser circuit breaker off, the amps dropped from 18 to 13, after 1/2 hour had a 10 degree drop from intake to exhaust. Another thing I noticed was I do not hear that pause before the second compreser kicks in. I would go ahead and replace the PC board, but I do not understand why the low amp draw.

DancinCampers · 05-18-2016, 04:11 PM

One check in the heat mode, early in the morning, spray water on the outside coil and see if both upper and lower half frost up.

mikf · 05-18-2016, 04:50 PM

Quote:

Originally Posted by DancinCampers

One check in the heat mode, early in the morning, spray water on the outside coil and see if both upper and lower half frost up.

will try that and let you know, but it will have to wait until fri. have to get an MRI tomorrow morning.:

Duner · 05-18-2016, 06:07 PM

I had a problem of compressor #1 rubbing a copper line in the #2 circuit and lost all freon. I'm pretty sure it was pulling about 17 amps, so my suspicion is low or no freon in the #2 system.

In 2008 I documented the process of pulling the a/c out and repairing a couple of things inside. I've had this document available to forum members to download HERE I suggest you take a look at the steps to get it open and the recommendations that I and other members have made. I've gotten great feedback on the success that many members had repairing it themselves and saving big $$$.

In regards to repairing it or throwing it out. Mine is 12.5 yrs old and running strong, including 6 yrs fulltiming. Unless you have lots of rust or something big, all the major components are still available.

You may very well have an additional problem with the Coleman Mach thermostat. That multi-function slide switch is very problematic. It is two slide switches ganged together and as they wear out they don't settle into the precise connection and so it puts the control board into invalid states. Sometimes you can fiddle with the switch to get it to work correctly. I think some folks have found the t-stat on Amazon or Ebay for a very good price.

Good luck,
Bill

mikf · 05-18-2016, 07:27 PM

Bill, I have read that link before and I just read it again before I read this message. Are you saying if I am low on freon that the compressor would pull less amps? Is there ports to test pressure and fill or would the tech have to add them? Good to hear from on the site, haven't seen any post from you lately.

Duner · 05-18-2016, 08:02 PM

Quote:

Originally Posted by mikf

Bill, I have read that link before and I just read it again before I read this message. Are you saying if I am low on freon that the compressor would pull less amps? Is there ports to test pressure and fill or would the tech have to add them? Good to hear from on the site, haven't seen any post from you lately.

Yes, when the freon is low or empty, the compressor runs but is more or less just idling and doesn't nearly have to work as hard. So the current for #2 compressor is maybe 3 amp instead of 8-10 amps. In my case when it leaked out, it left a lot of oily residue on the outside coils, so it was pretty obvious. There are no schrader valves and it needs to be added for service.

I located a mobile A/C repair shop that does repairs on refrigerated semi-trailers. I had my unit pulled out with the lid off when he arrived. He soldered the hole in the leaky tube, added the schrader valve, and added the freon. He was in and out in 45 minutes and it cost me $113 as I recall. I took the time to clean the inside of the unit, especially the coils.

mikf · 05-20-2016, 07:12 PM

Quote:

Originally Posted by DancinCampers

One check in the heat mode, early in the morning, spray water on the outside coil and see if both upper and lower half frost up.

Did that this morning. after 45 minutes no frost upper or lower. I think I will follow Bills procedure and get the top off and see what is going on inside.

bluepill · 05-20-2016, 07:33 PM

I had good A/C performance, but poor heat performance on my C/M basement unit. Found that the electric wire spade connector to one of the reversing valve solenoid coils was loose. Re-crimping solved the problem. Suggest you inspect those connections when you have the top off.

Bug512 · 05-21-2016, 06:06 AM

Hello, you might want to read through one of my old posts.

Link here

Sounds like you have a circuit that is out of gas.

mikf · 05-22-2016, 08:39 PM

Quote:

Originally Posted by DancinCampers

One check in the heat mode, early in the morning, spray water on the outside coil and see if both upper and lower half frost up.

I took the unit out today, when running in the heat mode the top half is cold to touch and the bottom is warm to touch. I see what I think is an oil residue in the bottom around one of the lines, so now I have to figure my next move.

Bug512 · 05-23-2016, 03:01 AM

Download all the manuals at the manufactures website and call a residential / commercial HVAC company. Depending on where the leak is they might bad able to blaze it and recharge.
Can you post a picture of where the leak is ?

DancinCampers · 05-23-2016, 09:19 AM

If the number 2 compressor is running but not drawing comparable amps it is more than likely low/out of freon in the #2 circuit. The freon also cools the compressor, so outside coil is warm.

If the #2 reversing valve is not operating the #2 circuit in the indoor coil would be cold.

Hikerdogs · 05-23-2016, 02:33 PM

Quote:

Originally Posted by pasdad1

How does it work in cooling mode?

The system has 2 sets of coils normally referred to as a condenser and an evaporator. When in the cooling mode the set of coils facing the outdoor louvered vent on the rear passengers side is the condenser. Here the hot high pressure gas coming from the compressors is cooled to a high pressure liquid.

The high pressure liquid moves through the tubing to an expansion valve where the flow is restricted. The restricted flow allows the liquid to expand and turn back into a low pressure gas. As the liquid expands to a gas it cools. The cool gas is then run through the second set of coils known as the evaporator. The gas cools the coils and surrounding fins. Air is blown across the cold coils. The now cooled air is then transported through the ceiling ducts to the ceiling outlets.

The system also has a switching valve. When the heat mode is selected the switching valve reroutes the Freon in the opposite direction through the system. The set of coils that was the condenser when in the cooling mode now becomes the evaporator. The coils that were the evaporator now become the condenser.

The heat generated by compressing the low pressure gas to a high pressure gas goes through the indoor coil first. It heats the coils and surrounding fins. Air is blown across the hot coils. The now warmed air is transported through the ducts to the ceiling outlets.

To be assured of proper heat transfer the coils must be clean. Winnebago recommends cleaning the outdoor coils a couple times per season. This can be accomplished by removing 2 screws in tabs under the louvered vent at the rear passengers side of the coach. The door will swing up so you can use either a soft brush or water hose to clean the coils. Be sure the system is not running when you clean the coils.

mikf · 06-06-2016, 08:10 PM

thanks for all the replies and here is the end result. after some long thought I decided on a new unit. $2648 free delivery. yea I know I could have had it fixed cheaper, but was worried that something else would go wrong on the road and I would be at some repairmans mercy. I did the work myself thanks to Dunners instructions and pictures, plus while waiting for delivery I took care of any rust in that area. now I have to get rid of the old one.