Dash air temp

[melvonnar]

My car says that the air temp comming out of the vent should be between 38 and 44; shouldn't the temp comming out of the motorhome be the same temperature?

[Batman_777]

You're referencing the temp of the AC air? Gennerally, it should be around 20 degrees colder than the outside air or unconditioned air. This may vary widely due to humidity, AC unit efficiency, duct work, blowers, recirculate, fresh air, etc etc.

I had an Expedition that would freeze you out (32 degree air), my truck on the other hand... I keep a thermometer in the air vent to see if it is cooling at all. Ford says it is within specs. Who's specs I ask? Shore ain't mine. Don't foget the cooling efficiency changed when we could no longer use Freon and they went to other types of cooling.

[melvonnar]

The reason I'm asking is the air conditioner compressor went bad and I had it replaced, the new compressor put ot 38 degree air; only problem ;,it had a leak and it was replaced with another one. The new one only puts out 54 degree air; the tech is telling me that its ok, I don't think so, when the other compressor put out 38 degree air.
I'm not to happy with 54 degree air. And I'm $900 poorer.

[mick]

The normal accepted air temp from dash air in autos, or any vehicle, is
50 degrees when the air outside is 80.

Was the air temp outside the same on both compressors?

[Batman_777]

54 degree air coming out if the outside temp is 80 is within cooling specs. Maybe the 38 degree air is why the compressor went bad. The new compressor is not working as hard. Wait!! the cooling affect is a result of liquid to gas expansion. The compressor returns the gas back to liquid which generates heat. The liquid then goes through an expansion process again that causes cooling. Air is blown over coils to cool the air. The reverse process is what a heat-pump does.

The compressor takes the refrigerant (the liquid that turns to gas) and under pressure by the compressor is forced back to a liquid. That's its job.

So why would just changing the compressor alter the air cooling effect?

Different coolant? Efficiency? Power or duty of the compressor? Coolant fluid check? Air in the line? Clog, Water in the line? More to come.

[Midniteoyl]

different freon charge... just .5 oz can make a diff in a small system...

[melvonnar]

Quote:

Originally Posted by mick The normal accepted air temp from dash air in autos, or any vehicle, is 50 degrees when the air outside is 80. Was the air temp outside the same on both compressors?

Yes

[melvonnar]

Quote:

Originally Posted by Midniteoyl different freon charge... just .5 oz can make a diff in a small system...

You may have something there; I'm taking it back monday to see if they will check it.

[melvonnar]

Quote:

Originally Posted by Batman_777 54 degree air coming out if the outside temp is 80 is within cooling specs. Maybe the 38 degree air is why the compressor went bad. The new compressor is not working as hard. Wait!! the cooling affect is a result of liquid to gas expansion. The compressor returns the gas back to liquid which generates heat. The liquid then goes through an expansion process again that causes cooling. Air is blown over coils to cool the air. The reverse process is what a heat-pump does. The compressor takes the refrigerant (the liquid that turns to gas) and under pressure by the compressor is forced back to a liquid. That's its job. So why would just changing the compressor alter the air cooling effect? Different coolant? Efficiency? Power or duty of the compressor? Coolant fluid check? Air in the line? Clog, Water in the line? More to come.

So many questions; so few answers.

[RinkersRanch]

Quote:

Originally Posted by Batman_777 54 degree air coming out if the outside temp is 80 is within cooling specs. Maybe the 38 degree air is why the compressor went bad. The new compressor is not working as hard. Wait!! the cooling affect is a result of liquid to gas expansion. The compressor returns the gas back to liquid which generates heat. The liquid then goes through an expansion process again that causes cooling. Air is blown over coils to cool the air. The reverse process is what a heat-pump does. The compressor takes the refrigerant (the liquid that turns to gas) and under pressure by the compressor is forced back to a liquid. That's its job. So why would just changing the compressor alter the air cooling effect? Different coolant? Efficiency? Power or duty of the compressor? Coolant fluid check? Air in the line? Clog, Water in the line? More to come.

Sorry but I had to jump in a little here. I have no disagreement with everything else you said here, BUT, . . . The compressor only pumps gaseous refrigerant. Cold gas coming in hot gas going out. The condenser turns the gas to a liquid.

[She and I]

I just charged ours myself....40 degrees in driveway and 38 on the road.
54 degrees is not exceptable to me..........JMHO!
Richard

[melvonnar]

Quote:

Originally Posted by She and I I just charged ours myself....40 degrees in driveway and 38 on the road. 54 degrees is not exceptable to me..........JMHO! Richard

Agreed: 54 degrees is not exceptable to me either.

[TXiceman]

High fan, high idle (1300 to 1500 RPM), a properly charge dash A/C should have an air temp in the mid to low 40's deg F.

The poor performance of the compressor could be improper charge, bad TXV (thermal expansion valve), plugged filter drier (it should have been changed when they changed the compressor), moisture in the system freezing in the TXV (system not properly dehydrated when repaired), wrong compressor size, wrong compressor pulley (compressor speed too slow), check the damper door on the heat side and the water valve to the heater coil (putting a heat load on the A/C system and mixing in warm air).

The condenser takes the high pressure gas and condenses it into a high pressure liquid. This liquid is expanded in the TXV to a lower pressure and a colder temperature. It evaporates (turns into a vapor) in the evaporator absorbing the heat in the coil. The vapor or gas is picked up by the compressor and compressed to a higher pressure where it will condense at a higher temperature and the cycle starts over.

An graphic explanation can be seen here....Automotive Air Conditioning Systems

Here is how to recharge the unit.....How Does A/C Work - An Automotive Air Conditioning Description

Here is a video on how to charge the system....

Checking Automotive A/C Pressures (updated) - YouTube

I disagree with the 2000 rpm on a motorhome (1300 to 1500) and fan needs to be high speed and recirculated air.

A lot of the information you get from non A/C folks is not accurate and a lot is based on hear-say. I have spent since before 1970 working on refrigeration and A/C. This is why I will tell people to take to a shop if they are not up to speed on A/C work.

ken

[melvonnar]

Quote:

Originally Posted by TXiceman High fan, high idle (1300 to 1500 RPM), a properly charge dash A/C should have an air temp in the mid to low 40's deg F. The poor performance of the compressor could be improper charge, bad TXV (thermal expansion valve), plugged filter drier (it should have been changed when they changed the compressor), moisture in the system freezing in the TXV (system not properly dehydrated when repaired), wrong compressor size, wrong compressor pulley (compressor speed too slow), check the damper door on the heat side and the water valve to the heater coil (putting a heat load on the A/C system and mixing in warm air). The condenser takes the high pressure gas and condenses it into a high pressure liquid. This liquid is expanded in the TXV to a lower pressure and a colder temperature. It evaporates (turns into a vapor) in the evaporator absorbing the heat in the coil. The vapor or gas is picked up by the compressor and compressed to a higher pressure where it will condense at a higher temperature and the cycle starts over. An graphic explanation can be seen here....Automotive Air Conditioning Systems Here is how to recharge the unit.....How Does A/C Work - An Automotive Air Conditioning Description Here is a video on how to charge the system.... Checking Automotive A/C Pressures (updated) - YouTube I disagree with the 2000 rpm on a motorhome (1300 to 1500) and fan needs to be high speed and recirculated air. A lot of the information you get from non A/C folks is not accurate and a lot is based on hear-say. I have spent since before 1970 working on refrigeration and A/C. This is why I will tell people to take to a shop if they are not up to speed on A/C work. ken

I agree:
As with all information one may get from the internet; you must seperate the wheat from the chaff; (good, from the bad). I called a Toyota garage to get a ball park figure to work with; the AC tech told me that with engine RPM at 1200; rescirculate max air on AC; temp in center air outlet should be 45 degrees or less. driveing down the road, the temp should be even lower. I would have to believe he is correct.

The 54 degrees I have is quite a bit too high.
The shop that did the work for me is trying to convince me that 54 degrees is the best I should expect. They have a 90 day warrenty on the recept that I received when I paid the bill; now what do I do becides complain?