Troubleshooting Mach 8 Ultra low profile A/C

NJKris · 04-13-2019, 03:04 PM

Brand new trailer, picked up in November, it was too cold to test AC at the time. Went to do some work out there today, plugged into 20 amp circuit, no other loads on circuit, AC is blowing same temp air as is inside trailer 82 deg, even after 15 minutes. I cycled off then back on, same thing. I can hear and feel vibration of compressor running. Yes, temperature dial on unit is turned all the way to cold (I can hear compressor come on as I turn it to cold). There is no external thermostat.

I was so excited to go on our maiden voyage on 4/25, and now this. Yes, I know I don't NEED A/C, but it was one of the draws of buying an RV, to camp in comfort.

Any tips from any of you HVAC guys would be appreciated. I don't have any tools to measure coolant pressures or anything like that, but I am ok with a multi-meter.

MR.M · 04-13-2019, 03:10 PM

Quote:

Originally Posted by NJKris

Brand new trailer, picked up in November, it was too cold to test AC at the time. Went to do some work out there today, plugged into 20 amp circuit, no other loads on circuit, AC is blowing same temp air as is inside trailer 82 deg, even after 15 minutes. I cycled off then back on, same thing. I can hear and feel vibration of compressor running. Yes, temperature dial on unit is turned all the way to cold (I can hear compressor come on as I turn it to cold). There is no external thermostat.

I was so excited to go on our maiden voyage on 4/25, and now this. Yes, I know I don't NEED A/C, but it was one of the draws of buying an RV, to camp in comfort.

Any tips from any of you HVAC guys would be appreciated. I don't have any tools to measure coolant pressured s or anything like that, but I am ok with a multi-meter.

Go up pull the cover off and make sure the condenser fan is still in one peice . They have had a problem with them falling apart even while just sitting

cavie · 04-13-2019, 03:15 PM

Quote:

Originally Posted by NJKris

Brand new trailer, picked up in November, it was too cold to test AC at the time. Went to do some work out there today, plugged into 20 amp circuit, no other loads on circuit, AC is blowing same temp air as is inside trailer 82 deg, even after 15 minutes. I cycled off then back on, same thing. I can hear and feel vibration of compressor running. Yes, temperature dial on unit is turned all the way to cold (I can hear compressor come on as I turn it to cold). There is no external thermostat.

I was so excited to go on our maiden voyage on 4/25, and now this. Yes, I know I don't NEED A/C, but it was one of the draws of buying an RV, to camp in comfort.

Any tips from any of you HVAC guys would be appreciated. I don't have any tools to measure coolant pressures or anything like that, but I am ok with a multi-meter.

You can't measure coolant pressures as you can on a home unit. RV compressors are sealed units and have no service valves installed.

You can put an amprobe in the AC line and check for 12/13 amps to be sure the compressor is running.

NJKris · 04-13-2019, 03:41 PM

thanks guys, will pull cover up top and look. My EMS is showing 118v, 8 amps being drawn when i turn unit on. It is a 13.5k BTU unit.

NJKris · 04-13-2019, 04:33 PM

Pulled outside cover, fan is working great. Compressor is very warm, almost hot to touch, feels like it's running. The tubing going into top of condenser coil felt like ambient temp. The tubing (very skinny, almost like a capillary tube) going into bottom of condenser coil was very cold. The 8 amp draw was on low cool, up to 9 amps on high cool.

dward51 · 04-13-2019, 04:44 PM

Quote:

Originally Posted by NJKris

thanks guys, will pull cover up top and look. My EMS is showing 118v, 8 amps being drawn when i turn unit on. It is a 13.5k BTU unit.

Get someone to watch the EMS closely. When you turn on the AC, it should spike a lot higher than that for startup. It will only be high for a second or so though. Also there should be a delay between when the AC starts up and the compressor actually kicks on. That delay device may be bad and it's not actually kicking the compressor, just the fans.

Or the thermostat could be wired wrong. Do you have a remote thermostat or is it the one on the Mach 8 housing? Finding a trailer with something wired wrong is not exactly a rare thing.

Also the Mach 8 has a high pressure safety switch. Once it trips, you have to totally remove AC power from the Mach 8 for it to reset. Try turning the Mach 8 totally off, and then flip the breaker for the AC to "off" for about 30 seconds. Then I would put the unit on high cool with the temp set to the warmest possible temp (compressor will likely not come on at this point). Then slowly turn the temp setting knob towards a colder setting, you should feel and hear the compressor kick in when you hit a setting below the temp inside the trailer (if it's working).

fonzie · 04-13-2019, 04:48 PM

Find the nameplate data and see how much full load current it should draw when running.

cavie · 04-13-2019, 05:01 PM

Quote:

Originally Posted by NJKris

thanks guys, will pull cover up top and look. My EMS is showing 118v, 8 amps being drawn when i turn unit on. It is a 13.5k BTU unit.

Coleman I found draws 12.1 amps running load.. Me thinks you have a bad compressor. It's under warrantee yes?

NJKris · 04-13-2019, 05:11 PM

Having wife standing out by EMS to tell me amps when i turned unit on was no help at all. The readout keeps cycling and wife was clueless about what I wanted her to watch for, even after explaining it. I have one of those multimeters with induction clamp, I don't know if that will work. I can't wait to drive 3 hours to dealer, just to have them tell me they have to order a new relay or something and have to bring it back.

NJKris · 04-13-2019, 05:13 PM

Yes, it's brand new. So they will probably have to replace entire unit? I don't see any easy way to replace the compressor, unless they solder one in and have a way to evacuate and recharge without fittings.

cavie · 04-13-2019, 05:18 PM

Quote:

Originally Posted by NJKris

Having wife standing out by EMS to tell me amps when i turned unit on was no help at all. The readout keeps cycling and wife was clueless about what I wanted her to watch for, even after explaining it. I have one of those multimeters with induction clamp, I don't know if that will work. I can't wait to drive 3 hours to dealer, just to have them tell me they have to order a new relay or something and have to bring it back.

A clamp it on meter is exactly what you need. Put it on the compressor lead only. just the hot wire. Should be a tag telling you the Full Load Running amps.

NJKris · 04-13-2019, 05:56 PM

Used the clamp on multimeter to check current on black lead to compressor. Upon start up, showed 5.XX, close to 6, then settled down to low 5's. Scale was set to 2/20 amps. Cavie, on this scale how many amps is this? The label under the AC cover shows the compressor amps should be 11.4, BCSC amps or something like that, don't know that acronym.

NJKris · 04-13-2019, 06:22 PM

Quote:

Also the Mach 8 has a high pressure safety switch. Once it trips, you have to totally remove AC power from the Mach 8 for it to reset. Try turning the Mach 8 totally off, and then flip the breaker for the AC to "off" for about 30 seconds. Then I would put the unit on high cool with the temp set to the warmest possible temp (compressor will likely not come on at this point). Then slowly turn the temp setting knob towards a colder setting, you should feel and hear the compressor kick in when you hit a setting below the temp inside the trailer (if it's working).

Did that, no joy. I can feel and hear compressor start, no differential in return/supply temperature.

cavie · 04-13-2019, 06:55 PM

Quote:

Originally Posted by NJKris

Used the clamp on multimeter to check current on black lead to compressor. Upon start up, showed 5.XX, close to 6, then settled down to low 5's. Scale was set to 2/20 amps. Cavie, on this scale how many amps is this? The label under the AC cover shows the compressor amps should be 11.4, BCSC amps or something like that, don't know that acronym.

I was looking for full load running amps. Don't know what the BCSC stands for but I guessing it is fla as it's very close to what I copied in one of my previous posts at 12.1. I think your compressor is shot. You are 6 amps short of what it draws when running.

Actual start up would be upwards of 15/18 amps I'm guessing. It is only for a short time.

NJKris · 04-13-2019, 07:05 PM

I am calling manager of Camping World in morning. You know, God forbid you troubleshoot everything and tell them over the phone all the details, and they say, 'we'll have a new AC unit ready for you when you come by and will swap out units'. I guess that would be too easy. I'm expecting it go like this, "well we can't make a determination until a tech looks at it". Then, I'll drive the 6 hours round trip to the dealer, for them to say, "yeah, you need a new unit". Then if I'm lucky, they'll call me in a month, and I have to drive another 6 hour round trip for them to swap it out. But the next available service appointment will be in 3 months. Yeah, I'm aggravated.

cavie · 04-13-2019, 07:32 PM

Quote:

Originally Posted by NJKris

I am calling manager of Camping World in morning. You know, God forbid you troubleshoot everything and tell them over the phone all the details, and they say, 'we'll have a new AC unit ready for you when you come by and will swap out units'. I guess that would be too easy. I'm expecting it go like this, "well we can't make a determination until a tech looks at it". Then, I'll drive the 6 hours round trip to the dealer, for them to say, "yeah, you need a new unit". Then if I'm lucky, they'll call me in a month, and I have to drive another 6 hour round trip for them to swap it out. But the next available service appointment will be in 3 months. Yeah, I'm aggravated.

This issue is more common than you think. They just might have a unit in stock.

NJKris · 04-13-2019, 07:33 PM

Thanks for the glimmer of hope man!

dward51 · 04-13-2019, 11:24 PM

If the compressor is coming on and there is no temp differential in the lines and the compressor is running on lower amperage than expected, that sounds like the coolant has leaked out and the compressor is not having to build any pressure. Ie, it's a warranty issue and internal problem to the AC unit.

And I would expect them to swap the entire unit out and not try to fix it. Especially on a new trailer.

NJKris · 04-14-2019, 06:54 AM

I am hoping when I try to call the manager in the morning, he will see it that way.

Walholler · 04-14-2019, 03:27 PM

You do not have to drive three hours to the dealer. Contact the manufacturer of your AC unit and they can give you the name of a local authorized repair facility for their product. Make sure that the manufacturer will cover the cost of repairs through the repair facility. I had the exact same problem with our Crusader Lite, it had a Dometic air conditioner. Dometic authorized the repair and unit was replaced with new like item within two work days. Your dealer, nor the manufacturer of your RV warrants the AC unit and most other items installed, including the tires.

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