Repair or replace A/C?

Alas not enough info in the first post.. The "Fix" could be anyting from a 10 buck part to complete replacement of the rooftop unit to a loos wire (no parts at all).

Now, In my case. it required a new rooftop module.. The new one is 11% more cool for the same amount of electricity. Good deal.

Thanks for your quick responses!!! I will check the capacitors/relay prior to replacing the whole unit.

psa0298 wrote:
I will add a bit more detail...maybe shed a little light. The A/C unit is a Coleman Super Mach. It has settings for fan only and low/med/high a/c. The fan blows in all positions. When I turn the A/C on I hear the compressor kick on but no cold air. The compressor gets hot (I have the same A/C unit on the back which works and it does not get hot while running)

Yeah- it does sounds dead. I take it this is a standard air distribution box, with knobs for temp and fan speed/cool? If you hear the compressor come on, let it run for a bit, then turn it off, then right back on- if it has lost the charge, it will come right back on, if there is still something in there, it will bog down.

j-d wrote:
Their model designations are confusing, but it sounds like our Mach 15, except you have three fan speeds and we have only two.
Yes the compressor will get HOT. Blower motor too, actually.
When you hear it "kick on" can you tell if it's actually spinning up, or if it's sitting in a "locked rotor" state? The trick is that it'll look like Locked if the Start Device and/or Running Capacitor has failed. It could also be spinning up but not providing cooling because
1. Refrigerant Leaked Out
2. Internal Compressor Failure
Either would mean Problem in Sealed System which = Replace A/C
But! Still a very good chance of things like defective capacitor(s). Our Coleman has a Fan Run Capacitor, and yours is clearly Good. Then it has a Compressor Run Capacitor (suspect in this case), AND some kind of Start Device. On ours, Start consists of a Capacitor AND a cut-out device. Ours is a Relay. Others could have a PTCR device.
I wish we were camped together. With my Meter, Clamp-On Ammeter, and the spare capacitors I carry along, could tell you real quick whether you should replace or not.
WHOA! WAIT! You can test your bad unit by Substitution! Swap the suspect parts with same from your working A/C! With POWER OFF, take a photo of the wiring (aid in reassembly), short the Capacitors across the terminals (might be holding a charge) then disconnect, remove, and switch the Compressor Start and Run devices to the non-working unit. Power it up and see if it starts. If it does, you can get fancy and try to tell if it's Start or Run that's bad, but you can buy both for around $30 from Amazon, eBay, etc. Capacitor will be marked with its microfarad rating, probably 40mfd at 370VAC, and a SUPCO SPP6E Start Device will replace both the Start Capacitor AND its Relay or PTCR device.

Good post and advice. Also the clamp on amp meter is a good investment. Make sure it is one of the new ones that reads both AC and DC.

Their model designations are confusing, but it sounds like our Mach 15, except you have three fan speeds and we have only two.
Yes the compressor will get HOT. Blower motor too, actually.
When you hear it "kick on" can you tell if it's actually spinning up, or if it's sitting in a "locked rotor" state? The trick is that it'll look like Locked if the Start Device and/or Running Capacitor has failed. It could also be spinning up but not providing cooling because
1. Refrigerant Leaked Out
2. Internal Compressor Failure
Either would mean Problem in Sealed System which = Replace A/C
But! Still a very good chance of things like defective capacitor(s). Our Coleman has a Fan Run Capacitor, and yours is clearly Good. Then it has a Compressor Run Capacitor (suspect in this case), AND some kind of Start Device. On ours, Start consists of a Capacitor AND a cut-out device. Ours is a Relay. Others could have a PTCR device.
I wish we were camped together. With my Meter, Clamp-On Ammeter, and the spare capacitors I carry along, could tell you real quick whether you should replace or not.
WHOA! WAIT! You can test your bad unit by Substitution! Swap the suspect parts with same from your working A/C! With POWER OFF, take a photo of the wiring (aid in reassembly), short the Capacitors across the terminals (might be holding a charge) then disconnect, remove, and switch the Compressor Start and Run devices to the non-working unit. Power it up and see if it starts. If it does, you can get fancy and try to tell if it's Start or Run that's bad, but you can buy both for around $30 from Amazon, eBay, etc. Capacitor will be marked with its microfarad rating, probably 40mfd at 370VAC, and a SUPCO SPP6E Start Device will replace both the Start Capacitor AND its Relay or PTCR device.

I will add a bit more detail...maybe shed a little light. The A/C unit is a Coleman Super Mach. It has settings for fan only and low/med/high a/c. The fan blows in all positions. When I turn the A/C on I hear the compressor kick on but no cold air. The compressor gets hot (I have the same A/C unit on the back which works and it does not get hot while running)

my ac did that too. It was a 12 year old unit. Terminal end broken on start capacitor was found and capacitor replaced. Cold air again and not very much $.

x2 what Chris said. If it was cold and simply stopped, it could be as simple and inexpensive as a connector/connection, capacitor, switch etc. We had a Coleman that age that was blowing cool not cold and cleaned it per instructions Chris has on the RV.net Blog. It cooled very well again after that.
Your problem sounds like the Fan runs but the Compressor does not. Blowing but not Blowing COLD, correct? From my experience, I would not condemn a rooftop A/C on age only. Now, if diagnosis indicates leaks or a bad compressor, YES I would not fool with it. Would replace.

I just had a problem with the AC on my 10 yr. old trailer. I could hear the compressor running, but there wasn't any air movement. From searching online, I learned that it could be a blown capacitor, or possibly the fan motor. Took it in for diagnosis, and it was the capacitor. It was around $200 to fix, but better than replacing the AC on a unit that I plan on selling within 6 months.

A wee bit of diagnoses seems to be in order- "not blowing cold" could mean replacing a $.07 terminal. I am puzzled that you are capable of R&Ring the unit, but not diagnose?