NO a/c NO A/H

Topic: NO a/c NO A/H (Read 1943 times) previous topic - next topic

Re: NO a/c NO A/H

Reply #25 – January 15, 2022, 04:19:34 pm

Quote from: GleamB – January 15, 2022, 04:09:36 pm

Any ideas as to how to trace it?
This isn't my strong suit

I'd start by inspecting the plug and cleaning it up. Low hanging fruit. After that I suppose it's time pop that wood panel/run off the wall and see what's back there. Maybe a mouse chewed something up. I have no idea where it runs... that might be a Rudy question.

I'd probably let this thread percolate for half a day before I started tearing things up. Someone may be able to chime in and suggest some low hanging fruit to inspect

Re: NO a/c NO A/H

Reply #26 – January 15, 2022, 05:14:35 pm

Will do
I can wait

Re: NO a/c NO A/H

Reply #27 – January 15, 2022, 05:43:30 pm

It is like a 6 wire phone cable. Rear goes to the front. Then there is a coupler nd then it goes straight to the front end, left to the driver's side overhead cabinets then through the cabinet floor and down the column where the thermostat is. Any of the connections or plug in connectors might be suspect. Both AC units have a 12v wire and a ground. Power to the thermostat likely comes from the front AC.

"Like a six wire phone line" but maybe not exactly. Usually these data cables have the ends reversed from one end to the other. One side of the flat cable usually has a ridge and the other side is smooth.

Re: NO a/c NO A/H

Reply #28 – January 16, 2022, 09:47:27 am

Glenn,

If both the new and old thermostats occasionally come on with attempted use and then go blank, I would suspect the phone cable or the phone plugs are the problem because the 5 button thermostat and the micro-air usually are very reliable. Both of them use digital communication so the analog style thermostat will not work.

After you have checked for bad fuses, the red and black wires in the plugs supply the 12 VDC. Green and yellow for data.

Check to see if the plugs are clean and fully seated in their phone jacks at both the thermostat and at the air conditioners. Also, water leakage causing corrosion, mice eating the cable or vibration are common causes of this type of failure. I also have seen bad inline couplers (sometimes used to convert cable types) on these lines near the air conditioner jacks.
As an easy test for bad cables is to buy another data cable. Or with the proper crimping tool and plugs, convert a phone cable to a data cable. String it through the air to make the substitute connections. At Walmart these data cables are "straight "phone cables and Amazon calls them "reverse" phone cables. Home Depot and Lowes may have data cables too.

Just like looking for your car keys, you will find the problem in the last place you look.

Jim

Re: NO a/c NO A/H

Reply #29 – January 16, 2022, 12:17:05 pm

The original t-stat did not light up when I turned on the switch
The new unit did not light up when I plugged it in
It came with no instructions
I imagine that, if there was 12 v power, then BOTH would light up
I would have to strip the wire near the t-stat to get a probe on the black and red lines
Unless there is a better way

Re: NO a/c NO A/H

Reply #30 – January 16, 2022, 12:23:42 pm

Glenn, go to their website and download their installation/operation manual for the easy touch!

Re: NO a/c NO A/H

Reply #31 – January 16, 2022, 12:29:46 pm

Quote from: GleamB – January 16, 2022, 12:17:05 pm

The original t-stat did not light up when I turned on the switch
The new unit did not light up when I plugged it in
It came with no instructions
I imagine that, if there was 12 v power, then BOTH would light up
I would have to strip the wire near the t-stat to get a probe on the black and red lines
Unless there is a better way

Has anyone verified that the thermostat gets 12 volts directly and not through the phone cable? When I switched out my 13.5K for a 15k I thought the 12 volts were sent through the phone cable. If so you need to go to the source which is the circuit board on under the cover on the roof unit which might explain weather issue. There is also a red and black 12 volt supply under the air register cover that you could verify voltage.

Re: NO a/c NO A/H

Reply #32 – January 16, 2022, 12:32:49 pm

Do not strip the wires or cut off the plug to read the voltage. Big mistake.
Use small, straightened paper clips or straight pins held to the meter probes to read the DC voltage on the plug's contacts.
If you found 12 volts on the plug then with it plugged in, try looking for 12 volts on the back of the thermostat - with the switch In the on position.
Jim

Re: NO a/c NO A/H

Reply #33 – January 21, 2022, 02:10:30 pm

I have not tested the 12 volt yet. How do I determine which wire is black and red without striping the main wire?
ALSO....
I left the switch to my original t-stat "on" for about two days. Then, it MAGICALLY fired up my a/c unit, one night. The next day, I plugged in the new, high dollar t-stat that I was told to get.
It lit right up, also. I need to read the manual, to understand how to use it, but for now I am still using the old one.
Let me know if anyone wants the new one, when I get back to the States, as this clearly is NOT the problem.

Re: NO a/c NO A/H

Reply #34 – January 21, 2022, 03:36:07 pm

The only wiring connection to the thermostat is the phone-like flat cable.

If you are having intermittent power issues pull down the inside AC covers and verify the 12v plus connection and the ground connection.

Re: NO a/c NO A/H

Reply #35 – January 21, 2022, 03:48:15 pm

IHi Glenn,

I would be interested in your old thermostat. 3 zero 8 4 four zero 5 one 5 four JIm

Re: NO a/c NO A/H

Reply #36 – January 21, 2022, 11:06:12 pm

If you are having intermittent power issues pull down the inside AC covers and verify the 12v plus connection and the ground connection.

[/quote]

OK
Where do I look for it?
How do I recognize the connection?
Not the phone cable, but a separate wire?

Re: NO a/c NO A/H

Reply #37 – January 21, 2022, 11:22:45 pm

There 12v +wire will most likely be white and the ground wire, green. Grounds are connected to the frame opening towards the front near the 120v box. 12v + wire probably comes out just to the right of the box.

Pull down the screen/filter cover from the inside cover. AA I recall there are four screws to remove to drop the inside cover.

Re: NO a/c NO A/H

Reply #38 – January 22, 2022, 11:44:05 am

Once again, thanks, Roger!

Re: NO a/c NO A/H

Reply #39 – January 25, 2022, 09:19:42 pm

Glenn.

In the phone type plug for the Dometic 4 and 5 button thermostats, use opened safety pins held against the voltmeter probes to be able to reach the contacts between plastic dividers of the plug. Normally the red is positive and black is negative for 12 VDC, but who knows how different manufactures have wired it. The green- and yellow-colored wires normally observed in the plug are for data transfer to and from the A/C circuit boards. They may show some much lower DC voltages as well - unrelated to the power source. you are looking for. You may need to cross-check all color combinations.
If no 12VDC voltage is found, check the fuse on the A/C circuit boards or suspect bad plugs, jacks and phone cable.
Jim

Frerichs Electronics
2002 U320 42'

Re: NO a/c NO A/H

Reply #40 – January 26, 2022, 09:23:44 am

Thanks
Will do

Re: NO a/c NO A/H

Reply #41 – March 30, 2022, 06:37:58 pm

Update:

As I had previously noted, this is an intermediate problem. When I did have power to the Comfort Control, I plugged in the Micro- Air Model 357 that was recommended to me. It, also, lit up. I reinstalled the original t-stat.

Yesterday, when I tried to fire up our air conditioner, there was no power. I had our Mobil RV repairman in my coach, working on my Microphor problem. We believe that the problem is with the control circuit board on the front unit. When I did have power to the t-stat, everything worked fine. He informed me that these boards are hard to find. In a past post, about replacing air conditioners three years ago, David S told me he got one on E-bay. I will be going up on the roof to find the model number of the board and try to find one, when we get back to the states. Can my existing board be repaired??

ALSO....I may want to sell the Micro- Air, since I don't believe it is the T-stat. Anyone wanna buy it from me, unused, new

?
When I get back to the states in May.

Getting warm here.

Re: NO a/c NO A/H

Reply #42 – March 30, 2022, 06:39:13 pm

PIcture....

Re: NO a/c NO A/H

Reply #43 – March 30, 2022, 06:44:07 pm

Quote from: GleamB – March 30, 2022, 06:39:13 pm

PIcture....

I was coveting that thermostat before I bought the Furrion system.

Why isn't all of this stuff Bluetooth by now?

Re: NO a/c NO A/H

Reply #44 – March 31, 2022, 09:15:58 am

So I have a similar issues with my AC. I can turn on my 3 button thermostat and it lights up. BUT the view on the thermostat only shows zone 1. When I go to AC nothing happens. In investigation I disconnected the phone cable from the fron to rear AC and the front AC worked. Nothing of course from the rear. The 4 button duo therm of course still shows only zone 1. No zone 2. ALSO the front AC works but is continuous and the fan runs constantly. I did buy the duotherm 5 button thermostat and 2 control boards but have yet to install. Is there something simple that may be the cause before I go ahead and try the upgrade. Saw lots of talk about a fuse in the control board and phone wire going bad. Maybe the cause.
Help and knowledge would be appreciated!!

Re: NO a/c NO A/H

Reply #45 – March 31, 2022, 11:35:43 am

Hi Peter,

Your email mentioned 3 button and 4 button thermostats.

When the 4 button thermostat push buttons begin to fail, it temporarily scrambles the chip in the thermostat. Replacing the push buttons usually brings it back to normal, though occasionally resetting of the thermostat is needed afterwards.

Five button thermostats will not work with a 4 button A/C system. Hope you can return it or consider upgrading to a five button system - lots of work and greater expense.

Get hold of me for more help,

Jim Frerichs
308-440-5154

Re: NO a/c NO A/H

Reply #46 – March 31, 2022, 03:27:16 pm

Sorry finger issues. 4 button and 5 button

Re: NO a/c NO A/H

Reply #47 – March 31, 2022, 07:25:50 pm

I think that he said he had a 5 button tstat and new 5 button upper boards. Sometimes you can spray electrical contact cleaner on the cable ends and the couplers. The Dometic couplers are not the same as telephone couplers.

Re: NO a/c NO A/H

Reply #48 – March 31, 2022, 07:36:06 pm

I just got done spraying contact cleaner and gently swabbing with Q Tip.
STILL no power to t stat. Went up on roof and opened front a/c unit. 3 amp fuse good. NO apparent corrosion or loose wires. will go check behind white panel tomorrow. Then....

Re: NO a/c NO A/H

Reply #49 – March 31, 2022, 07:52:15 pm

Is there 12 volts at the 3 amp fuse? Thanks

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