AC Thermostat Bypass - Short Cycle |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Topic: AC Thermostat Bypass - Short Cycle Posted: 15 Jul 2021 at 7:51pm |
Can't seem to find any good answer on this...
I am trying to trouble shoot another AC short cycling issue. I had the problem, replaced thermostat and it went away. Yesterday, ran AC all day no issue. Today AC just short cycles - usual fan comes on, compressor kicks in, cool air blow for a few seconds, compressor shuts down, fan shuts down, unit rests for a minute or two and cycle repeats. Weird problem cuz it has happened before, but only intermittently. I thought replacing thermostat might fix it. Loose wire in control box? Replace control box? I do have EasyStart but the problem happened before and after EasyStart. It is not cold air blowing on thermostat. It is not a source voltage problem. So I am thinking maybe another thermostat gone bad? Can I bypass it and force fan/compressor on? Not sure what wires to jump. |
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 16 Jul 2021 at 6:09am |
If you let the interior get warm and then set the thermostat as cold as possible does it still short cycle? If so the you might suspect the compressor or Easystart. If not then it's probably the stat.
If it's the stat then you might want to get one with an adjustable temp differential aka hysteresis. Not sure how to wire it in your specific case but the lite W1209 thermostat boards are very versatile and operate on 12v. So all they need are 4 wires, two for 12v power and 2 that provide a contact closure to run the a/c. Fully configurable for heating, cooling, hysteresis, setpoint, and time delay. You can load the the temp sensor remotely and very inexpensive too. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 6:28am |
Got me thinking there OG. Yesterday, it was 97 interior. Skin temp was prolly 120+. Short cycled from get go.
I just turned it on this AM w/74 interior and thermostat set @ 55. Meat locker time. After 5 minutes I'm measuring 43.5 @ AC duct. The day before when it worked great, It wasn't quite as hot as yesterday. I'm seeing a pattern here. Seems like maybe @ certain high temp it's not working. That's not good. I had noticed a similar behavior prior to EasyStart ( I think ) so what's going on? f
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 6:41am |
I'll just keep it on auto today w/stat set to 74.
Should be 90 or so here by noon, so we will see. f
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 7:48am |
Got a good tip from Micro-Air. Has built in diagnostics:
Will check this afternoon when it warms up. f |
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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TheBum
Senior Member Joined: 26 Feb 2016 Location: Texas Online Status: Offline Posts: 1407 |
Posted: 16 Jul 2021 at 10:34am |
MA makes an EasyStart with Bluetooth now so you can check it with your phone. I plan to get that one to add to my 196 whenever it arrives.
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Alan
2022 R-Pod 196 "RaptoRPod" 2022 Ram 1500 Lone Star 4x4 Three cats |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 2:54pm |
My email to Micro-Air. I know this is not their problem, but it sure is damn frustrating!
====================================== @ 8:00 AM I set the stat to 72 and auto fan. The ambient temp was 74 as well as trailer inside. For four hours the unit worked flawlessly, maintaining 72+- inside. @ 12 noon ambient was 92, roof temp => 128, AC shroud temp => 155 Inside was a comfortable 72+- I shut down the system for 2 hours. @ 2:00PM ambient was 95, roof temp => 128, AC shroud temp => 160 Inside temp was a hot 100 Started system, stat set to 72 and auto fan. The unit shortly begin cooling and seemed to be working normally. After ten minutes or so and inside temp @ 85 I pushed the thermostat up as far is it would go - 90. After a minute or so the unit shut down. I did not wait 3 minutes. After maybe a minute, I lowered the thermostat to 72. The fan kicked in, the compressor did not. The EasyStart showed lights D22 D23 glowing ( Power Interruption ). I guess that is normal? I shut the system down for 5 minutes or so and the started up again with stat set to 72 and auto fan. It has been cooling since. So, all in all, it seems everything is working exactly as it should? So why did it short cycle and not work yesterday? I did let it rest between attempts. What other tests can I do? If it is a loose wire, where to look? I guess I have to wait until it happens again and see if the EasyStart shows any other error? The only other observation is that I removed the inside air distribution cover just to check for obstructions. Sure seems to blow a lot more air than when it is on. Anyway, if you have any suggestions I would greatly appreciate them. Intermittent problems are a bitch!! |
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
|
fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 4:01pm |
OMG. 10 minutes after I posted that, it started short cycling again!!
Total cycle 4:39 seconds. After it shuts itself down, fan comes on @ 1:30. Compressor comes on @ 3:00. Compressor shuts off @ 4:00. Fan shuts off @ 4:39. Man, this is driving me nuts!! I'm thinking it must be control box. What else could it be? |
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 16 Jul 2021 at 6:41pm |
Hmmm. Don't know specifically what to suggest as I haven't seen a similar problem.
I'm assuming you're in mains power. Is your line voltage good? It could be a compressor thermal overload brought on by hot conditions and/or low line voltage. What did the Easystart indicate when you got the short cycle. Have you run the advanced Easystart troubleshooting procedure? |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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fwunder
Senior Member Joined: 04 Oct 2013 Location: New Jersey Online Status: Offline Posts: 1676 |
Posted: 16 Jul 2021 at 7:18pm |
'Bout time to talk with the HVAC guys up the road.
Yeah, OG, the EasyStart does just what it is supposed to. When it does short cycle, it keeps compressor from starting up for three minutes after startup. Then, compressor just shuts down after 30 seconds or a minute. No error. Cycle repeats. It's like a total freeze up, I think, although I see no ice with shroud off. Haven't dismantled condenser coil cover. Voltage while running ( line ) measured 126v. Same symptom with line or generator. It's been 4 hours shutdown and I just tried it again. Short cycling. If it starts up normal in the morning...should I try to adjust it with a 12 gauge slug? Damn
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2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6 Yes, those are wild ponies dining on grass while dumping tanks! |
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