Skip to main content ↑ ↓
Topic: NO a/c NO A/H (Read 2223 times) previous topic - next topic

Re: NO a/c NO A/H

Reply #21 –
As I mentioned above, this has been an intermittent problem....the WORST kind of problem.
I did order the VERY EXPENSIVE T-stat, as recommended.
I did NOT install it, as my original t-stat decided to light up and operate.......
Until today.
This problem seems to occur after the t-stat hasn't been used for a while, as in when it is in storage, or recently, not used for either the A/C nor heat. I don't know if that has any relevance.
So......I decided to install the plug and play Micro Air
No instructions came with this thing.
I plugged....
NO PLAY
It doesn't light up !!!!!!??????
What is my next step? I wanted to test to see if the phone jack was getting power, but I only have standard tester.
Any help would be greatly appreciated

Re: NO a/c NO A/H

Reply #22 –
If I recall correctly, it's require no set up to use at the screen. You should be able to plug that telephone cable in and start controlling things immediately. It makes me suspect your power source or a ground going to it. A loose ground may explain the symptoms you were seeing with the old T stat.

Re: NO a/c NO A/H

Reply #23 –
Any ideas as to how to trace it?
This isn't my strong suit

Re: NO a/c NO A/H

Reply #24 –
I agree with Elliot, it should be "plug and play". If you you want remote controlling, that's another story, ie, Bluetooth, Wi-Fi.

Re: NO a/c NO A/H

Reply #25 –
Quote from: GleamB –
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 –
Will do
I can wait

Re: NO a/c NO A/H

Reply #27 –
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 –
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 –
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 –
Glenn, go to their website and download their installation/operation manual for the easy touch!

Re: NO a/c NO A/H

Reply #31 –
Quote from: GleamB –
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 –
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 –
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 –
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 –
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 –


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 –
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 –
Once again, thanks, Roger!

Re: NO a/c NO A/H

Reply #39 –
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'