Forum Discussion

SC_camper's avatar
SC_camper
Explorer
Aug 17, 2014

Colman roof ac unit replacement?

Let me explain my problem then Ill ask a question. Our last trip in June, the ac would get cold but would freeze up after a couple hours. We have had that problem before but always found the problem to be a dirty filter and once it was a clogged evaporator core. I thought about low freon but it was getting cold. I thought the problem might be a bad thermostat since the compressor wouldn't cycle on and off. I replaced the thermostat before our trip this weekend.

This weekend, the ac wouldn't get cold at all. The fan and compressor comes on as it always has but the evaporator core doesn't get cold. So now I believe the problem is low freon. None of my local rv shops will charge the system, they say replace it. I have finally accepted the thought of a replacement over a repair.

The ac unit is a Colman Mach system, laterally ducted and the controls are in the ceiling unit. If I replace the roof unit, is it best to replace the ceiling unit too? The new roof unit will require the same ceiling unit as I all ready have. Since the fans and compressor comes on, should there be a problem with the ceiling unit?

Thanks for any input.

10 Replies

  • j-d's avatar
    j-d
    Explorer II
    Aug 21, 2014
    Do you plan to have the new "upper" installed or do it yourself? I have not personally done one but from all I've read (and watched a professional do one) it isn't a bad job IF you have help to get the old down/new up, and protect the roof from snags and tears.

    I SO wish there was a way to cool things down for what sounds like a great weekend! Anybody got a room/window unit you can bring out there and temp install it? Maybe the escape window? You could still punch it out of there in event of a fire. I'm thinking Blanket, Cardboard, Duct Tape (of course!), Bungees or Rope.
  • SC_camper's avatar
    SC_camper
    Explorer
    Aug 21, 2014
    Thanks for the help j-d. I had all ready cross referenced my model number at the site you provided and have found a few sites to buy from and called several dealers throughout my area. I can pay the $120 freight charge and still pay $50 less than anywhere local.
    The trip this weekend was a group trip with 22 sites for our group. I went out after work Thursday and set up for the weekend. DW and DD were coming out Friday, until I let them know that the ac was broken. I put up with the heat until Saturday evening and packed it up.
  • j-d's avatar
    j-d
    Explorer II
    Aug 21, 2014
    Sounds like your A/C was well maintained. If it was clean, sensor in place, you ran on high fan, ducting was clear, and it still froze up, it may well have been leaking down. Any venture into the sealed system is going to price you toward a new unit. The website or a well-versed sales person should be able to point you toward a new unit, and let you know if a new upper is compatible with your existing lower.
    We're like your DW. We have temps in the upper 90's with feels-like over 100. I keep spare capacitors for the A/C on board. I've repaired the blower on site. If I couldn't keep A/C running, we'd be going HOME.
    Good Luck!
  • SC_camper's avatar
    SC_camper
    Explorer
    Aug 21, 2014
    j-d wrote:
    This is the Coleman WebSite. It should tell you which current model A/C replaces what you have now.
    Before you replace, do you know if the Compressor is actually running? If it is NOT, could be something simple keeping it from starting. If it IS running, is the small tube leaving the compressor HOT? Is the larger tube returning to the compressor COLD? Can you measure Current Draw? You'd need an AC (alternating current that is) clamp-on ammeter. If it's running, the AMPS should match the running rating on the compressor tag. If it's a lot HIGHER, compressor is dragging internally and probably running hot. "Could" be overcharged, but hardly possible since it has no service ports. If AMPS are LOW, it's likely undercharged or empty. OR, rare but happens, the motor portion inside the sealed shell has come separated from the compressor portion. Either of those and the A/C is junk unless you have access to free parts and/or free technician labor.
    Have you eliminated ducting problems and the position of the Defrost Sensor?


    I know the compressor is running and the fan is running. I didn't check the temps on the lines from the compressor. I don't have an AC amp clamp. I replaced the thermostat before this trip and the defrost temp probe is in the correct location. I removed the filter and placed my hand on the evap core. It doesn't get cool let alone cold.

    Since everything runs as it did when it was cooling(and freezing up), I don't think the problem is in the ceiling unit. A new roof unit will fix the problem. I hate to spend the money on a new roof unit if there is a cheaper fix, but also think any money spent to have it diagnosed further is money that could go towards a new unit. Camping season is picking up for us and DW said get it fixed. She doesn't want to have ac problems while we are out of town. Last weekends trip was to the local lake, DW and DD stayed at home after hearing the ac was broke.

    Thanks for every ones help.
  • j-d's avatar
    j-d
    Explorer II
    Aug 20, 2014
    This is the Coleman WebSite. It should tell you which current model A/C replaces what you have now.
    Before you replace, do you know if the Compressor is actually running? If it is NOT, could be something simple keeping it from starting. If it IS running, is the small tube leaving the compressor HOT? Is the larger tube returning to the compressor COLD? Can you measure Current Draw? You'd need an AC (alternating current that is) clamp-on ammeter. If it's running, the AMPS should match the running rating on the compressor tag. If it's a lot HIGHER, compressor is dragging internally and probably running hot. "Could" be overcharged, but hardly possible since it has no service ports. If AMPS are LOW, it's likely undercharged or empty. OR, rare but happens, the motor portion inside the sealed shell has come separated from the compressor portion. Either of those and the A/C is junk unless you have access to free parts and/or free technician labor.
    Have you eliminated ducting problems and the position of the Defrost Sensor?
  • ksg5000's avatar
    ksg5000
    Explorer II
    Aug 19, 2014
    I know many people only buy the upper unit when replacing - don't see any reason you can't do the same. Make sure you locate your model number before talking with seller.
  • SC_camper's avatar
    SC_camper
    Explorer
    Aug 19, 2014
    I've looked at the scratch and dents on Adventure rv. How will a "dented pan" affect the operation of the ac unit? Could it cause it to leak?
  • TXiceman's avatar
    TXiceman
    Explorer II
    Aug 17, 2014
    By the time you pay to have the Schrader valves soldered in, a vacuum pulled and new refrigerant added, you are well on the way to at least 1/2 of the cost of a new unit. Most A/C techs do not like to work on the small sealed units as the correct charge is critical to proper operation.

    Ken
  • SC_camper's avatar
    SC_camper
    Explorer
    Aug 17, 2014
    I've talked to a couple residential ac guys. Told them that I would put in the valves and put the system under vacuum, if they would just gas it with 14.7 ozs of 22. No takers.

    PPL has the best price on new units, I've looked at the scratch and dents on Adventure rv. How will a "dented pan" affect the operation of the ac unit? Could it cause it to leak?
  • newman_fulltime's avatar
    newman_fulltime
    Explorer II
    Aug 17, 2014
    call a regularac guy they can put the schredder valves on and recharge it and repair.
    or look up adventure rv look under scratch and dent get a new ac alot cheaper

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