Basement air delay starting

PORCHDOG · 02-05-2013, 02:51 PM

I have an '07 Adventurer with basement air. I have found that when in electric heat mode the thermostat calls for heat and the unit starts and runs for maybe 10 seconds then shuts off. In about 4 minutes it does the same thing. Then sometimes it continues to run. It keeps the coach warm but I wnder why it only runs for 10 seconds and shuts off. Any ideas what is happening?

Hikerdogs · 02-05-2013, 03:25 PM

If you have the thermometer set 4* or more below the ambient temperature the system will try to assist by running both the gas furnace and the heat pump until the differential between the set and the ambient temperatures is less than 4*. If the gas is not on or the furnace is inoperative the system will shut down.

If the outdoor temperature is less than about 37* (varies slightly from coach to coach) the heat pump will run for a few seconds then attempt to switch to gas heat only. If the gas is off or the gas furnace isn't working properly the system will shut down.

When the gas furnace attempts to start you should hear the sound of sheet metal rubbing as the fan opens the furnace air inlet. If you don't hear the noise either the door isn't opening properly or the sail switch is not detecting the open door. In either case the system will shut down to avoid overheating the heat exchanger or poisoning the occupants with carbon monoxide.

If the outside temperature is above 37* try setting the thermostat only 2* above the inside temperature. If the heat pump is working properly it should come on and stay on. The fan should come on and start blowing cool air immediatly. It should stay on and take a couple minutes before you feel warm air comming from ceiling the ducts.

PORCHDOG · 02-08-2013, 07:04 AM

OK, Hikerdog, sounds exactly what is happening. Now, how do I get to check the furnace air inlet and sail switch? Being here in Florida I have a small window when it is cold enugh to have the conditions you described. I really appreciate your reply and explanation.

DancinCampers · 02-08-2013, 07:34 AM

To check the gas furnace, turn t-stat to gas. Raise set temp above room temp. If it runs, raises temp, and turns off, then gas furnace should be ok.

When you say, in electric mode, unit runs for 10 sec, then shuts off, do you mean the basement compressors?

Hikerdogs · 02-08-2013, 09:20 AM

We have a Suburban 35,000 btu unit. I can't remember the model number off hand. The sail switch and inlet door for our furnace are part of the unit itself. To inspect and/or service it the furnace hs to be removed from the coach.

I was able to purchase the manual from our selling dealer when we bought the motorhome. If you know the serial number of your coach you can go online to the Winnebago parts catalog and see an exploded diagram of the furnace.

Parts Catalog

When you click on the link click on the "Service Parts List". It'll open another window where you can select the model year and provide the serial number. It should open a window with the build sheet for your coach. Information about the furnace is in the "Heating and AC Group"

Hikerdogs · 02-08-2013, 02:30 PM

Quote:

Originally Posted by Hikerdogs

We have a Suburban 35,000 btu unit. I can't remember the model number off hand. The sail switch and inlet door for our furnace are part of the unit itself. To inspect and/or service it the furnace hs to be removed from the coach.

I was able to purchase the manual from our selling dealer when we bought the motorhome. If you know the serial number of your coach you can go online to the Winnebago parts catalog and see an exploded diagram of the furnace.

Parts Catalog

When you click on the link click on the "Service Parts List". It'll open another window where you can select the model year and provide the serial number. It should open a window with the build sheet for your coach. Information about the furnace is in the "Heating and AC Group"

They've changed a couple things since I last used the online build sheet. When you enter the last 5 digits of your serial # you'll get to your build sheet. The sheet lists all the components in alphabetical order. When you get to the line "Furnace" look across the page for the part #. Copy it down and go to Google. Enter the phrase "Winnebago part number XXXXX" . It should come up with a pdf manual for your year and model coach. You will find the exploded diagram of your furnace in the "Heating and AC Group"

Jbmsr · 02-08-2013, 02:41 PM

Check to see if the roof vent is blowing at the thermostate. This will cause a very quick cycle in electric heat mode.

Quote:

Originally Posted by PORCHDOG

I have an '07 Adventurer with basement air. I have found that when in electric heat mode the thermostat calls for heat and the unit starts and runs for maybe 10 seconds then shuts off. In about 4 minutes it does the same thing. Then sometimes it continues to run. It keeps the coach warm but I wnder why it only runs for 10 seconds and shuts off. Any ideas what is happening?

PORCHDOG · 02-08-2013, 06:14 PM

The gas heater works normally and the roof air outlet is not aimed at the thermostat. When the thermostat is in electric heat mode, you can hear the AC unit switch on and runs but shuts off in about 10 seconds. I am not sure if it is only the fan or if the compressor is running too. Runs just long enough to circulate cold air and quits before getting warm. It does this several times every 4 minutes then it continues to run on one of the cycles. To pull the heater seems to be quite a job. It is out the rear wall in the end cap with no access from the interior.

Hikerdogs · 02-08-2013, 07:13 PM

Quote:

Originally Posted by PORCHDOG

The gas heater works normally and the roof air outlet is not aimed at the thermostat. When the thermostat is in electric heat mode, you can hear the AC unit switch on and runs but shuts off in about 10 seconds. I am not sure if it is only the fan or if the compressor is running too. Runs just long enough to circulate cold air and quits before getting warm. It does this several times every 4 minutes then it continues to run on one of the cycles. To pull the heater seems to be quite a job. It is out the rear wall in the end cap with no access from the interior.

If the gas furnace works fine on its own there's no need to remove it. The problem lies either in the thermostat, or the basement AC system. You can check to see if the compressor is running by either opening the outside panel then the control box and checking the LED's , or just stand by the panel and listen to hear if it kicks in.

Be sure to check that the circuit breakers in the main panel aren't tripped before you go outside. I made a similar mistake when the unit wouldn't cool properly. I had inverdently tripped a breaker when dusting them off. I called a tech and the first thing he asked was "Did you check the breakers". When I opened the panel I was embarassed to say the least.

If you don't hear it start you may have a problem with the starting capacitor, a bad switching valve, or worst case a siezed compressor. It's most likely a bad capacitor, but I would contact someone who services residential AC units to diagnosis it. It's very similar to a unit used in residential construction.

DancinCampers · 02-08-2013, 07:19 PM

I would further trouble shoot tstat and basement unit before pulling lp furnace.

What is the outside temp when this short cycling happens? Does unit work ok in cooling mode?

I would remove fuse from tstat for a few minutes to cycle memory. Also clean switch contacts.

If you are comfortable with wireing, I would remove oneplace panel or Tstat, disconnect the 9 pin connector from tstat, and jumper pins 2 and 8 going to basement unit. (Double check your model tstat). This should put +12vdc (pin 2, red wire) on the wire that controls pc board (pin 8, white wire). (I am using the pub from my unit on my previous 2003 Adventurer).

If electric heat works ok, both compressors and fans turning on, then I would rule out basement unit pc board and suspect tstat.

Once the pc board receives control voltage on pin 8 it controls all operations of basement unit in heat mode. I do not believe the lp furnace would be involved in the very short cycling you mention.

10 second run time is very short. I suspect either tsat is dropping the 12vdc control voltage, or the basement pc board has an intermittent problem in the heat mode.

.