Tune Up Your AC System -- On a Winnebago (Freightliner) Itasca Horizon 40AD

[imnprsd]

My coach is a 2004 Itasca (Freightliner) Horizon 40AD and my AC was never working right for the last 3 years I have owned it. So I decided to do something about that and what I found was that I had a very clogged A/C Receiver-Dryer.

Since A/C systems are commonly a Freightliner supplied item I will post my A/C notes here.

NOTE: My 2004 Winnebago Diesel Pusher (350HP Cummins ISC 8.3) uses 1970-1990's A/C components from Mercedes, Ford, and GM. I guess the RV manufactures buy surplus parts and build their own systems. Hence, you also have to get parts from Winnebago at times as Freightliner will not supply you with some items.

Hopefully the attached .pdf will help you solve your AC problems in any RV you drive. MY PROBLEM WAS A CLOGGED RECEIVER-DRYER, and I replaced my TXV for good measure.

SEE .PDF ATTACHMENT.

Note: I still do not understand my gauge readings on my RV-A/C system. The High Pressure Side just does not want to climb above 140PSI and it's 80F outside, but my coach A/C system is blowing ice cold. Can anyone tell me if an RV with 40' of HP an LP lines will have different target pressures on the High Side vs. a regular truck?

And does anyone know the Spec's on my 2 High Side Switches? One is a Binary Switch and the other is a Condenser Fan Switch.

[FIRE UP]

imnprsd,
Good evening Sir. I surely want to thank you for taking all that time and effort to do an outstanding writeup and, with pics and all. That's great. It's especially great to us because, we have a basic sister ship to your. Ours is the Itasca Horizon 36GD with the CAT C-7 330HP.
We've owned our coach now for just over 7 years and, in the first couple of years of ownership, the dash A/C was fairly good. But, in the last year or two, it was completely dead. So, a friend here in Lake Havasu had some A/C work recently done on his coach and recommended a place. Well, not knowing anywhere else, I took his recommendation.

Since then, and around $600 later, that A/C is functioning flawlessly. I would have liked to save the $600 and do it myself as, I've done 98% of the repairs/alterations/modifications/maintenance and a whole lot more ever since we've first parked this thing at home. But, A/C work has never been my bag. It's pretty much Greek to me. I know just enough to REALLY get myself (and the coach) in trouble.

But, due to another thread on A/C temps, I checked ours at the ducting and, with outside ambient temps hovering at 90+ (at the time I was checking the A/C temp) I was getting 43-45 degrees at the dash ducts. I figured for this kind of system, with a pump and fan and condenser, 36' away from me, that 43-45 degrees is pretty good. What ya think?
Scott

[imnprsd]

You are very welcome and thank you for your compliments.

I think if your engine AC temperature gets any colder you're going to freeze the evaporator.

Therefore your mechanic tuned your AC perfectly. Do you know if they flushed out the oil in your system too?

I'm asking cuz I tend to think that you can't get 40+ temperature differences kinds unless you change the oil too. Which begs the question: What's the best way to verify you have the right amount of oil in a closed RV - A/C system? Hopefully someone with more experience can answer that for us.

Do they replace your Receiver- Dryer or TXV or both?

The good news is that I can run down the road with 90 degree temperature out side and not have to turn my dash A/C fan higher than the number 2 setting on the dial!!!

[gatorcq]

Except for the part, "The A/C is a Freightliner Supplied Part". The only item that FL supplies is the A/C compressor. If you would call FL, they would confirm this, Least ways on the series from 2002 to 2008 XC chassis

[Skip426]

The "who supplies what component " in the , motor home dash A/C system , is a moving target , as outlined in this document from Evans Tempcon.
Even with the document there are issues , as they say they don't supply the condenser electric fan , but it shows up in their parts department listings .
Just replaced the engine mounted A/C compressor ; from Freightliner ; and the dryer , crossed to an AC Delco part. Original dryer also shows on the Evans web site and the bracket for it has a Evans / Tempcon parts tag.

[imnprsd]

Who knows if there is a 20PSI/40PSI compressor switch in these systems?

Is it mounted back by the compressor in the engine compartment? Or does this part NOT exist as it normally would in a car AC system?

There is a binary switch on the HP line going into the TXV-Expansion Valve and it will keep the compressor on if you jumper it. But you can't force the compressor to work in this mode. Still, this maybe the controlling part. I just don't know?

Anyway, I'm looking for conformation that I do NOT have another electrical A/C switch hidden somewhere? Thanks for your help.

[ladagobago]

I had the same problem several years ago. Checked the pressure on the condenser fitting and everything was crazy. The fan switches were no good. the tension pulley bearing was "gone", and when I took off the Receiver/dryer, it was fully clogged.

I flushed the system, but in new oil, preplaced all the defective parts. Most all the parts were available on line as standard AC components. Finally found that the expansion valve was crap too so replaced that. After a bit I realize that Binary switch thermocouple was no good too. contacts were corroded and crap.

After all that I vacuumed the system to dry it and checked for leaks. once it held I put a primary charge on the lines and let it sit overnight. Vacuumed it again to be sure there was no air and put in a final charge

The pressure should relate to the ambient temp by a factor of 15 degrees. The Air out of the vent should be near 47 to 52 degrees. To cold and the evaporator might freeze up.

[imnprsd]

Here is a more descriptive approach on HOW TO OPTIMIZE YOUR DASH A/C SYSTEM.

See attached .pdf

[ladagobago]

Originally Posted by imnprsd

Here is a more descriptive approach on HOW TO OPTIMIZE YOUR DASH A/C SYSTEM.

See attached .pdf

That is close to what I did. Make sure the condenser fan is operational too. I found blown fuses and also bad connections to the electric fan found behind the front bumper. The binary switch with the thermocouple which goes into the evaporator also was defective and intermittent. If your MH is older check the tension pulley bearings near the compressor. Mine was shot.

when charging the system, it is advisable to release a little gas bleed out of the charge hose to evacuate any air that might be introduced in the system. Use the HF IR temperature gun to check you temperatures out of the condenser and the output of the vents to confirm a good charge. Typically the condenser will be about 15 degrees hotter than ambient. The vents should be around 41 to 50 degrees. Make sure that the hot water shuttle valve is working properly. mine was not so I added a ball valve to manually turn off the hot water entering the air stream.

[rrtribble]

Just had my '07 Itasca 34H in for 48K PM. The mechanic servicing it informed me my air intake was almost completely clogged. He cleaned it out and added some coolant. Not only the AC work flawlessly but when I switched over to heat a couple of days ago it ran me out and unit was warm all the way back to the fridge. Dash AC cools down part of the coach beyond what it ever did before. Will be checking air intake annually and will be considering possibility of adding an air intake filter in front of it similar to house AC.Furnace systems.

[ladagobago]

Originally Posted by rrtribble

Just had my '07 Itasca 34H in for 48K PM. The mechanic servicing it informed me my air intake was almost completely clogged. He cleaned it out and added some coolant. Not only the AC work flawlessly but when I switched over to heat a couple of days ago it ran me out and unit was warm all the way back to the fridge. Dash AC cools down part of the coach beyond what it ever did before. Will be checking air intake annually and will be considering possibility of adding an air intake filter in front of it similar to house AC.Furnace systems.

Where is the cabin air filter located and how do you replace it. Is there a part number.

[DJJ]

Imnprsd,
Thanks for taking the time to document your repair. Two specific things you covered has helped me. My high side pressure like yours is on the low side, 175, but the low pressure is normal. The only thing I could find from other sites is the cause of low high pressure is a weak compressor. The second thing you mentioned is the time it takes the high and low side to balance out after the AC is shut down. 45 min. And mine still had not equaled their pressure. So thanks to your research my not so cool dash ac may have hope yet.

Jeff

[rrtribble]

Just got back on site.
Couldn't find my air filter but the intake is on the dash at the floor in front of the co-pilot seat. Looked at mine again and no way to insert filter over intake without cutting into dash.

[ladagobago]

Originally Posted by rrtribble

Just got back on site.
Couldn't find my air filter but the intake is on the dash at the floor in front of the co-pilot seat. Looked at mine again and no way to insert filter over intake without cutting into dash.

Same location as mine so I wonder how it is changed????