Continuing saga rear AC Dutch Star..need help

[Magredvet]

About a month ago, the rear AC stopped cooling and I got a mobile service out to diagnose the problem. Turns out the wires to the compressor were burned out so he ordered a new unit.
The new unit was installed, and after trying the heatpump, a strange issue occurred. The inside temp sensor for the new AC would give inaccurate readings ie 50 deg, when it was obviously much warmer (95 deg outside)
Talked to the tech and he had me reset the thermostat, twice, this seemed to fix it for a while, until this weekend. Now it has started jumping around again, press it one minute 66, a minute later 55, and always much lower than the actual inside temp, and therefore the AC will not run.
So....last night I put the thermostat into diagnostic mode, and it tells me the inside temp is 55 ...............it's over 80 in the bedroom, but also that the ambient temp sensor (for the heatpump) is reading 40 deg, when it is 80 deg outside .
For some reason the people who installed the unit will not come out and troubleshoot the issue, as they say it's nothing they did wrong ????
Any suggestions on what it might be ?...........could I have got a bad AC board from the factory, or is it something they did whilst installing the unit, which is why they won't come back ?
Either way I will never use this company again, but I need to get this fixed, certainly before summer comes around in TX again.
Any input would be appreciated
Thanks in advance

[JC2]

Originally Posted by Magredvet

About a month ago, the rear AC stopped cooling and I got a mobile service out to diagnose the problem. Turns out the wires to the compressor were burned out so he ordered a new unit.
The new unit was installed, and after trying the heatpump, a strange issue occurred. The inside temp sensor for the new AC would give inaccurate readings ie 50 deg, when it was obviously much warmer (95 deg outside)
Talked to the tech and he had me reset the thermostat, twice, this seemed to fix it for a while, until this weekend. Now it has started jumping around again, press it one minute 66, a minute later 55, and always much lower than the actual inside temp, and therefore the AC will not run.
So....last night I put the thermostat into diagnostic mode, and it tells me the inside temp is 55 ...............it's over 80 in the bedroom, but also that the ambient temp sensor (for the heatpump) is reading 40 deg, when it is 80 deg outside .
For some reason the people who installed the unit will not come out and troubleshoot the issue, as they say it's nothing they did wrong ????
Any suggestions on what it might be ?...........could I have got a bad AC board from the factory, or is it something they did whilst installing the unit, which is why they won't come back ?
Either way I will never use this company again, but I need to get this fixed, certainly before summer comes around in TX again.
Any input would be appreciated
Thanks in advance

Another example of so-called rv repair person/company which everyone needs to know about. After someone comes along with the correct info to help you get it fixed, I would make it a point post your unfortunate/unnecessary experience about this company here. It's free and only takes a few minutes of your time.

RV Service Reviews

[bruceisla]

Originally Posted by Magredvet

So....last night I put the thermostat into diagnostic mode, and it tells me the inside temp is 55 ...............it's over 80 in the bedroom, but also that the ambient temp sensor (for the heatpump) is reading 40 deg, when it is 80 deg outside .

Thanks in advance

Does this occur on each unit or just the rear? How many topside A/C units do you have?

[Magredvet]

Only on the rear, which was the unit that was replaced.
I have 3, and the other two sensors are working fine, Repair company tells me the thermistor for the rear unit has gone bad, but I don't believe in coincidences, especially as they had to unplug it from the old, and into the new.
I immediately thought that they had messed up the connection, but after resetting the CCC2, it worked ok for a month, but now the inside temp sensor is back to erratic readings. What surprised me was that the Ambient temp sensor is also reading (very low)

[bruceisla]

Originally Posted by Magredvet

Only on the rear, which was the unit that was replaced.
I have 3, and the other two sensors are working fine, Repair company tells me the thermistor for the rear unit has gone bad, but I don't believe in coincidences, especially as they had to unplug it from the old, and into the new.
I immediately thought that they had messed up the connection, but after resetting the CCC2, it worked ok for a month, but now the inside temp sensor is back to erratic readings. What surprised me was that the Ambient temp sensor is also reading (very low)

This is a shot in the dark but Dometic requires a separate/discrete 12vdc feed for 3 units. I.E. 2 units normally have 12vdc feed to unit 1 and unit 2 can be powered by the telco cable from unit 2. Unit 3 must be powered by it's own 12vdc feed and not from the telco between unit 2 and 3. It's possible your rear unit doesn't have it's own feed (either disconnected or missing). If the discrete feed is missing, the 12vdc from the telco is insufficient to correctly power the board in unit 3.

[Magredvet]

Thanks for the info, I'll try and check it out.
The unit was fine until they changed it out, so maybe they didn't reconnect it or is there a fuse that controls it ?
maybe they blew the fuse when connecting it up ?
Funny how it worked for a while tho ?............strange issue ?

["007"]

There are dip switch's involved on control board of AC but the CCC is seeing the 3D AC could be just a loose wire connection effected by temp changes.
AC & control wiring diagrams are in QT's 1 & 2.

[Magredvet]

Ok thanks for the info.
Update, I can't find any separate fused supply for the 3rd AC, only a 7.5 amp 12v fuse that controls the CCC2.
Latest issue when sitting last night .............unit set at 72deg, on COOL, Auto fan..............inside temp shows 32 deg F ...........the fan just suddenly starts up on the unit, high speed , and definitely no compressor.
Only way to get it to stop, was to turn the unit to OFF.
Surely this is a sign of a fault in the Ac board ?
Gonna tell the service guy about this latest incident, and see if it will convince him there's something wrong, other than the thermistor......
Why should things be so hard to get done ?...........at one time people used to take pride in what they did ............oh well !

["007"]

If your in Texas I would give BrooksW a call I'm sure he can help you, read thread his service number is there.
He travels all over the mid-west.

[Magredvet]

Thanks man, I will contact him.............he's just up the road in Cypress

[Magredvet]

So after all this time, all is still not well. Got the guy to come back out, this time he changed the board and the thermistor harness. Worked for 15 minutes , them back to erratic temp display. Guy comes out again, and changes thermistor, by splicing a new one to existing wire. Still no change.
At this point I'm thinking damaged thermistor wire, so I fed a new thermistor from the unit down through the return air vent. The unit ran fine for 25 minutes, then the indicated inside temp starts to drop, and the unit blows warm air. Does this sound like the evaporator is freezing up ?
I'm at my wits end with this, and have been paying for all these "fixes", as the company insists it's not their fault. I even mentioned about the discreet 12v to the rear unit, and the tech says, there was no supply that he didn't hook up .
So to recap, new unit, then new board and harness, finally new thermistor.
Surely all of the controls have been replaced (apart from the CCC2)...what on earth could be causing this ?
Should I post this in the RV systems and appliances section ?
I'm open to any and all suggestions

[lostinfla]

Originally Posted by JC2

Another example of so-called rv repair person/company which everyone needs to know about. After someone comes along with the correct info to help you get it fixed, I would make it a point post your unfortunate/unnecessary experience about this company here. It's free and only takes a few minutes of your time.

RV Service Reviews

Thanks for that. I just left a review for a mobile repair in GA. I wouldn't let the guy they sent work on my lawnmower much less our coach. Ended up doing the work myself with the parts he brought. For the bargain price of $810.00 for a 6" piece of hose and 11 gal of coolant, we were ready to go...

[bruceisla]

Originally Posted by Magredvet

So after all this time, all is still not well. Got the guy to come back out, this time he changed the board and the thermistor harness. Worked for 15 minutes , them back to erratic temp display. Guy comes out again, and changes thermistor, by splicing a new one to existing wire. Still no change.
At this point I'm thinking damaged thermistor wire, so I fed a new thermistor from the unit down through the return air vent. The unit ran fine for 25 minutes, then the indicated inside temp starts to drop, and the unit blows warm air. Does this sound like the evaporator is freezing up ?
I'm at my wits end with this, and have been paying for all these "fixes", as the company insists it's not their fault. I even mentioned about the discreet 12v to the rear unit, and the tech says, there was no supply that he didn't hook up .
So to recap, new unit, then new board and harness, finally new thermistor.
Surely all of the controls have been replaced (apart from the CCC2)...what on earth could be causing this ?
Should I post this in the RV systems and appliances section ?
I'm open to any and all suggestions

Well ... here's some more troubleshooting ideas (assuming you don't mind going on the roof):

1) Get this:
http://bryantrv.com/docs2/docs/ccc2diagnostics.pdf

2) In diagnostic mode, the CCC2 can read the sensors and the switches. Run the diagnostic and monitor the sensors for erratic readings. What happens ??

3) Get this:
http://tnt.rvia.org/unipop.cfm?v=3&oid=1559
Make up a short (3 feet is fine) communication cable see page 33 of manual for color code. Connectors and a roll of telco wire is available at Lowes. Make sure you observe the Dometic color code ... it is NOT the same as an off-the-shelf telco cable .... the connectors are wired differently.

4) Take the CCC2 off it's mount (depress retainer on bottom). Take it up on the roof to unit 3. Unplug the communication cable (from unit 2 to 3). Plug the short cable in and attach the CCC2. Power up the CCC2 and run unit 3 (you are eliminating a communication cable problem). What happens??

[Magredvet]

Ok, thanks for the info, I'll give it a try !.............