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Over the Road AC Not Working in the Cab

Yahoo Message Number: 23854
Hello

Our front dash AC is not blowing cool air. The system is called "over the road" AC and provides cooling air to both the dash and the bedroom while the engine is running.

The bedroom AC part is cooling at 41 degrees in the vent, so the compressor is working well. I find a fitting at the dash unit that is cold to the touch but the attached piping is warm.

The piping from the compressor in the engine compartment gives no clue as it seems to be well insulated. That piping splits forward and up to the bedroom wall. Both runs of pipe are neutral in temperature.

All the sliders and buttons on the dash controls seem to be doing their job via movement and sound observation of the AC/heater unit.

Has anyone successfully dealt with this problem or have any helpful hints to regain that cool air?

Thanks

Dean

95 CC Magna #5280

Re: Over the Road AC Not Working in the Cab

Reply #1 –
Yahoo Message Number: 23859
Dean

It sounds like you might have a plugged or inoperative expansion valve at the front evaporator coil.
The input line will be the smallest one and it will terminate at a relativly square block. This line carries the liquid refridgerant and the expansion valve controls the rate at which it may flow into the coil. If there is sufficant flow the outflow line (bigger) will be cool to the touch, if there is no flow then it will be warm. The only repair for this is to have a qualitied service tech pump down the system and replace the expansion valve and the filter/dryer assy, draw a vaccuum and refill the system. This is not a bad idea considering the age of the unit. The filter/dryer has a finite life. I replaced the one on my '93 SOB twice by 2004.

Dave (aka billy byte, my trusty hound) 2000 Allure 30443

Re: Over the Road AC Not Working in the Cab

Reply #2 –
Yahoo Message Number: 23864
It could be one of your "HCV" (Heater Control Valve). These (One for driver's side, one for passenger side) modulate the mix of hot/cold as called for by the hot/cold (red/blue)control knobs. I had same problem and replacing the HCVs did the trick.

Joe on-the-road at San Juan Is., WA '04 Allure 36 #31031

Re: Over the Road AC Not Working in the Cab

Reply #3 –
Yahoo Message Number: 23915
Is your fan working? If not, I would suspect the resistor pack in the fan control circuit. Or, a bad electrical connection due to corrosion on the resistor pack terminals.

Jim Hughes

2000 Allure #30511

Quote from: Dean
Hello

Our front dash AC is not blowing cool air. The system is

called "over the road" AC and provides cooling air to both the

dash

Quote
and the bedroom while the engine is running.

The bedroom AC part is cooling at 41 degrees in the vent, so the
compressor is working well. I find a fitting at the dash unit

that

Quote
is cold to the touch but the attached piping is warm.

The piping from the compressor in the engine compartment gives no > clue as it seems to be well insulated. That piping splits forward > and up to the bedroom wall. Both runs of pipe are neutral in > temperature.

All the sliders and buttons on the dash controls seem to be doing > their job via movement and sound observation of the AC/heater unit.

Has anyone successfully dealt with this problem or have any

helpful
 

Re: Over the Road AC Not Working in the Cab

Reply #4 –
Yahoo Message Number: 23918
Thanks to all for your responses. The Fan and all buttons worked, but no cool air at the dash on the outbound trip this weekend. On the return trip, nice cool air until we hit the 112 degrees area.
Must be a ghost electrical problem. Perhaps it will not fail again?

Dean

95 CC Magna 5280

Quote from: Jim Hughes
Is your fan working? If not, I would suspect the resistor pack in > the fan control circuit. Or, a bad electrical connection due to > corrosion on the resistor pack terminals.

Jim Hughes

2000 Allure #30511

[quote author=Dean"

>

> Hello
>

> Our front dash AC is not blowing cool air. The system is > > called "over the road" AC and provides cooling air to both the > dash

> and the bedroom while the engine is running.
>

> The bedroom AC part is cooling at 41 degrees in the vent, so the > > compressor is working well. I find a fitting at the dash unit > that

> is cold to the touch but the attached piping is warm.
>

> The piping from the compressor in the engine compartment gives

no

Quote
clue as it seems to be well insulated. That piping splits

forward

Quote
and up to the bedroom wall. Both runs of pipe are neutral in > > temperature.
>

> All the sliders and buttons on the dash controls seem to be

doing

Quote
their job via movement and sound observation of the AC/heater

unit.