2006 Monaco Dynasty Dash air conditioning problem

[monacoman06]

I have a 2006 Monaco Dynasty with a dash air conditioning problem.  The system quit cooling and I added Freon and it worked for about a day then quit cooling again.  I took it into a very knowledgeable technician and he recharged the system and found the AC condenser was leaking.   The condenser is mounted in front of the side mounted radiator in the rear.  While recharging the system he noted the high pressure side was reaching 500 PSI and shutting off.  He said that there needs to be some type of switch or something to make the hydraulic fans turn at a higher RPM to bring the condenser temperature down instead of an emergency type high pressure shut down of the compressor.  He felt that the high pressure in the system most likely caused the condenser leak and that if a new condenser was installed it would most likely start leaking because of the extreme pressure in the system.  He tried calling The RAV Group that apparently now owns the Monaco lines.  They were of no help in trying to diagnose why the pressure was getting so high.  If anyone has any ideas about what triggers the cooling of the side mounted AC condenser I would appreciate their comments.  I do not want to replace the condenser until I can get the extreme pressures reduced which will require that the cooling fans are cooling the condenser to reduce the temperatures and thus the pressure in the system.

Thanks, Jim

[sstgermain]

Is that on a Spartan Chassis . . . Maybe a call to them could help.

[richard5933]

Something doesn't sound right here. The tech is looking for a design problem, but presumably the system has been functioning for 12 years with the current design. Lots of things can cause the high side pressure to rise - a faulty fan clutch, a faulty fan, a blockage in the system, etc, etc. Is the tech certain that the existing fan is working properly?

I know that you say the tech is very knowledgeable, but if he recharged the system before establishing whether or not there was a leak I'd question that. When my system had problems, the tech first tried to evacuate the system and establish a vacuum. Only after the vacuum held overnight did he attempt to charge the system - first he did this with an inert gas to test if the system would hold pressure. Once it was confirmed that the system was sealed and able to hold pressure did he recharge it with refrigerant. In most areas of the country it is not permissible to recharge an a/c system without confirming that there are no leaks.

I agree with the above - call the company that manufactured your chassis and get a recommendation from them for a shop in your area qualified to diagnosis and fix this.

[manholt]

Richard.  Unless I'm way off base, the chassis on his coach is a Roadmaster!  REV Tech is the only link.  I agree with all the rest.

[richard5933]

1 hour ago, manholt said:

Richard.  Unless I'm way off base, the chassis on his coach is a Roadmaster!  REV Tech is the only link.  I agree with all the rest.

From the brochure, looks like you're correct. However, if this was my vehicle I'd find a commercial truck repair center with an a/c tech. Even better if they also work on buses. In Milwaukee we have a company called Lakeside International. They've done work on my a/c unit with great success. Odds are they'd be able to diagnose the problem and come up with a real solution.

Our coach has three separate a/c units - two house and the over-the-road system. None of them are magic and all operate on similar principles. Same for the a/c in a Roadmaster chassis. A qualified a/c tech should be able to diagnose and repair this problem.

[f442485]

Yes, it is a Roadmaster chassis. Your system is using R134a refrigerant and requires a higher pressure to work well. R134a at its best does not work as well as R12, but it is what it is. I don't think your tech did a complete diagnosis to confirm what the problem is. It is most likely the expansion valve. If it not been serviced since 06, it needs to be replaced. Normal operating pressures are about, Low side around 50psi and around 350 to 450psi. If the compressor is making 500psi or more, the compressor is working just fine.  

[hermanmullins]

Chassis manufacturers don't make air conditioners neither do engine manufacturers. Your problem needs an automotive a/c tech that knows his stuff.

I had an issue with mine. I checked all fittings. All were tight except one. I was able to tighten it less then 1/4 turn. I charged the unit, no more leak and it cools like a dream.

Herman 

[richard5933]

Not sure about the systems in the newer coaches, but ours takes 25 lbs of refrigerant. That's a lot of refrigerant and $$$. Because of that, if it ever develops a leak it's going to be leak tested before a recharge. We have a tell-tale lamp on the dash that lights up if there is a problem keeping the compressor from kicking in when turned on - the most common reason is low refrigerant due to a leak.

No shop is going to attempt to recharge any a/c system without a thorough leak test, often using a leak detector or dye. In Wisconsin it's illegal to recharge a system with an unknown leak status to prevent accidental discharge of refrigerant to atmosphere. I'm sure that this is the case in most states.

As a side note, be careful with the cans of refrigerant that can be purchased in box stores. They may say r134 on the label, but if one reads the small print it will be found that it is "r134 compatible" and actually contains something other than just r134. Often other gases are used, sometimes flammable, and often there are other things like leak sealants which may or may not be compatible with the rubber seals in the vehicle.

Not to be a stick in the mud, but there are certain systems on a vehicle where I consider a professional tech necessary, and a/c is one of them. I've gone down the DIY with a/c too many times, and every time it was money thrown away as the real problem still had to be solved down the road by a professional. At best the DIY was a stop-gap measure.

[manholt]

As Joe L. has said on numerous occasions, very hard to find a "professional Tech" today!  

[kaypsmith]

Most likely with a side mount radiator, the fan is probably hydraulic, the faster the motor turns the faster the fan turns as a result. Dirty condenser core can cause high pressure in the system just like the dirty condenser in your home AC. The dash air in every motorhome is totally different than the bus air on our bus conversions, most are rotary compressors like on most cars, while the bus air are piston type compressors, mine is a 5 ton unit designed to cool the entire bus, while dash air is actually designed to cool only the front seats of a MH. I agree that steps must be taken to lower the pressure, my starting place would be to clean the condenser core and of course the radiator, and I agree that a new expansion valve and drier if the compressor is making that pressure. A typical MH only uses 3 to 5 # of refrigerant in the dash air. Many side mount radiator systems also have an electric fan as a backup, look for that as well.

[dickandlois]

13 hours ago, Monacoman06 said:

I have a 2006 Monaco Dynasty with a dash air conditioning problem.  The system quit cooling and I added Freon and it worked for about a day then quit cooling again.  I took it into a very knowledgeable technician and he recharged the system and found the AC condenser was leaking.   The condenser is mounted in front of the side mounted radiator in the rear.  While recharging the system he noted the high pressure side was reaching 500 PSI and shutting off.  He said that there needs to be some type of switch or something to make the hydraulic fans turn at a higher RPM to bring the condenser temperature down instead of an emergency type high pressure shut down of the compressor.  He felt that the high pressure in the system most likely caused the condenser leak and that if a new condenser was installed it would most likely start leaking because of the extreme pressure in the system.  He tried calling The RAV Group that apparently now owns the Monaco lines.  They were of no help in trying to diagnose why the pressure was getting so high.  If anyone has any ideas about what triggers the cooling of the side mounted AC condenser I would appreciate their comments.  I do not want to replace the condenser until I can get the extreme pressures reduced which will require that the cooling fans are cooling the condenser to reduce the temperatures and thus the pressure in the system.

Thanks, Jim

Jim, Welcome to the Forum !

Could you list / Do you know who's AC system was used on your coach ?  

Denso is a large supplier for RV dash AC systems.  If you can get to the Engine area - The Compressor is visible in most cases.

Rich.

[monacoman06]

Thanks to all of you that submitted suggestions.  After more looking in to the problem, I think the issue is in the needle valve assembly that controls the hydraulic fans.  Monaco uses a valve assembly manufactured by Sauer Danfoss and patented by Monaco.  As the temperature rises, the valve opens to allow more hydraulic fluid to flow and thus increases the speed of the fans and more cooling.  I feel this is the valve/switch that the truck A/C  technician was looking for.  The RAV Group had no interest in trying to help diagnose the problem and has been very very unhelpful.  They are the group that bought out the Monaco brand.  A new hydraulic valve/switch from Monaco is approximately $1650.00.  Based on the cost of the new valve and a new condenser, I have concluded it will be much less expensive to pay for the extra diesel to run the generator and roof air conditioners rather than try to repair the dash air.  Thanks again to all of you that responded to my post.

Jim

[jleamont]

Jim, here is a link for a redesign for the hydraulic fan set up on the later Monaco coaches. I believe the redesign that caused all of the heartburn came along in 2003

http://sourcerv.com/conversion