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Old 05-12-2022, 12:22 PM   #1
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Dash AC Woes

Well, I've got something strange going on with my (Denso)dash A/C unit and admittedly, it is my weak point as far as knowledge is concerned.

Leaving Savannah, GA this morning my dash AC was working fine as we packed up and departed and about 10 miles into the trip south to head home, it stopped blowing cold air and was blowing the ambient air temp from outside.

Waited about 30 minutes and switched it back on again and it started blowing cold again. The co-pilot stuck a thermometer in the dash vent and it hoovered between 45 and 55 degrees underway.

It remained at those temps for another 30 miles and like before, began blowing ambient air from outside?

We continued to our current overnight stop here in Jacksonville, Florida and when we arrived, I turned on the dash AC again and it was blowing cold air as expected. The condensor fan was running as we sat idle and I could here and see that the compressor apperared to be functioning as normal with the clutch engaging?

So, for you gentleman that have a broader knowlege base of RV AC systems than I, what do you feel the issue might that is generating the symptoms I'm experiencing.

Thank you for your input. I have the Denso RV AC Manual with me on pdf to refer to.
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Old 05-12-2022, 12:40 PM   #2
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So your Denso dash section of the A/C unit was installed by your coach manufacturer .
Freightliner installed some sections while building your chassis ; compressor ,condenser, and pressure hoses from the engine to the front of the frame rail where the hose to the dash unit attach.
As per the diagram from Evans /Tempcon.

From your description of the issue ,two possibilities;
1; the refrigerant pressure in the system is right on the border line of being low and a slight top up is required .
2; the evaporator is freezing up , and has to thaw before proper operation can continue.

I have the Denso pdf and will read through and post anything else that comes to mind.
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Old 05-12-2022, 01:58 PM   #3
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If you have not worked on a/c systems.. if you are in Florida.. they should understand a/c better than anyone.. so hit a shop in Florida and get system checked out..
Or.. you can go into a/p store and get a book on basic automotive a/c repair.. it will save you a lot of money.. even if you let shop repair.. you can read up and understand if shop is just ripping you off.
Get a can of Freon and with low side gauge and try to top off.. for less than 30.00
A/c is not too hard to understand... if you got a book.. the book will give the correct pressure for air temp.. and get you close..
I would think that the state of Florida should have best a/c techs in the world... because they do it down there every day..
Good luck and keep us posted
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Old 05-13-2022, 01:32 PM   #4
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Thank you both for your responses.

I am waiting to arrive back home on Sunday before looking into the problem further, but I'm beginning to THINK I may have a relay going bad.

Today we drove from Jacksonville, FL to Ft. Pierce and the dash A/C worked fine the whole trip..........puzzling?

I intend to put a guage on the low pressure port to see if it is in fact low on R134A and if so, have a reputable AC tech come out and service it in lieu of filling it from a store bought DIY product.

It is my understanding and experience that RV dash AC systems are a bit more complex
and I certainly don't want to compromise the compressor, surpentine belt and possibly other components should the compressor fail (ie. sieze) from overfilling it...........especially underway.

Although you would think South Florida would be home to a number of AC Technicians, very few shops will touch an RV because it usually involves dismantling the dashboard to troubleshoot and/or fix a problem. They have plenty of work with vehicles.

Anyway, I'll jump off that bridge when I get to it.

Thanks again.......will keep you posted.
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Old 05-13-2022, 04:54 PM   #5
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So glad it all worked out for you.. have safe trip.. all the a/c I have seen.. if you ever need to get into dash.. is just 2 wood screws.. access is through area by pass side feet.. there is a kick plate.. 2 screws you find with magnet.. then pull kick plate out.. many times there are cigarette lighter or 110v outlet.. just unplug them and you are there.. you can get access to everything.. maybe takes 30mins.. you can check you door motors.. lube cabes.. and HVAC actuator rods.. and check relays.. bet you need to clean blower resistors pack..
Good luck and keep us posted
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Old 05-14-2022, 09:28 AM   #6
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Torbik;

If you look at the diagram posted by Skip 426 you will see the control system is vacuum operated. You will see a vacuum pump and vacuum ball & the control. Rubber hoses are attached to these controls The hoses have been known to crack where they are attached as they age.

Over the years I have had that happen to me a couple of times. If your problem persists I encourage you to check the connections for vacuum leaks. If you find a crack and you have ample hose a quick fix is cut off the hose by the crack and reattach the hose.

Good luck;
Don
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Old 05-15-2022, 07:35 PM   #7
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I would suspect vacuum control or your hot water valve
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Old 05-24-2022, 06:38 AM   #8
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Put indoor blower on High
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Old 05-24-2022, 10:59 AM   #9
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There was no information listed about your MH but if it is one included in the rear PDM recall that could be the problem as it was for us. The rear PDM distributes the power to both the compressor clutch and the condenser fan on ours and we had the same issues that you describe until it was replaced. Make sure you are not part of the recall before spending money on the AC system itself by calling Freightliner.
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Old 05-25-2022, 06:11 AM   #10
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Mine is a 2012, so not included in the Freightliner PDM recall campaign.

Having been under the weather since returning home after three months on the road and catching up on my home chores, I havn't had the time to look into it any further.

I will day that running from Ft.Pierce, FL back to my storage facility in Miami, the dash AC ran fine. So, it still remains a mystery at the moment.

When I do get to it, my first course of fire is to check the refrigerant level first and see if it boarders on the low side.

Will post my findings later at some point.

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Old 05-25-2022, 07:04 PM   #11
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Quote:
Originally Posted by Skip426 View Post
So your Denso dash section of the A/C unit was installed by your coach manufacturer .
Freightliner installed some sections while building your chassis ; compressor ,condenser, and pressure hoses from the engine to the front of the frame rail where the hose to the dash unit attach.
As per the diagram from Evans /Tempcon.

From your description of the issue ,two possibilities;
1; the refrigerant pressure in the system is right on the border line of being low and a slight top up is required .
2; the evaporator is freezing up , and has to thaw before proper operation can continue.

I have the Denso pdf and will read through and post anything else that comes to mind.
Hey Skip, would happen to have a guess at how many pounds of freon should be in the dash A/C on a 37 ft, Coachmen DP?
Compressor is on engine in rear (obviously) and connections are up front.
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Old 05-25-2022, 07:08 PM   #12
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There is a tag from Evans, up front on the box containing heater core. The spot on the tag where it says how much freon should be in the system, is blank.
Go figure.
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Old 05-26-2022, 11:04 AM   #13
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This is from the Evans Service Manual. Good luck.
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Old 06-28-2022, 10:47 AM   #14
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Just to close out this thread, I had the refrigerant checked by a mobile truck/RV AC technician and after setting up his gauges, he showed me the 134A was very low.

He said it is not that uncommon in a 10 year old rear diesel pusher

He slowly charged the system back to the appropriate level considering the ambient temperature while monitoring both the high and low pressures.

The AC is now blowing between 43-45 degrees out of each vent and I'm hoping that is the solution to what I was experiencing.....we'll see on the next trip.
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