2007 American Coach tradition 40J dash air repair

[Genevatexan]

Our coach is in a local shop with the dash air not cooling, the compressor clutch not engaging, and blown fuses on the compressor clutch fuse under the entry step. The AC shop is fumbling with the compressor install and freon charge, cannot find the appropriate Freon charge, and does not seem to know what the pressures should read on the high side and low side to figure it by the gauges. Spartan is closed, and closed early on Friday and refused support saying their system had crashed. We need help understanding how to guide this low end shop to get this done right.

The shop says replace compressor, which is a Comfort Air Compressor. The installed unit was aftermarket, a Seltec, which the shop is replacing with OEM. They got the compressor from Spartan and then asked us what the freon charge should be.

Our '07 Tradition 40J is built on a Spartan Mountain Master chassis, has a 400 Cummins engine, side radiator and the AC charge port is on the drivers side in the front basement door. The repair shop says the condenser is on the right rear.

The chart attached seems to indicate that the AC should take 3 lbs because it is a Rear side mounted condenser, under 2011 model, under 500 hp engine. They put 3 lbs in and the AC does not cool. They overcharged it at one point and had 400 lbs of pressure on the high side and it was cooling to 43 degrees but the head pressure sounds too high so they backed it off and matched our recommendation for 3 lbs based on this chart, which won't cool. Any ideas on what we need them to do? We have canceled our trip starting this weekend and are dead in the water... help appreciated.

[Skip426]

Spartan didn't do the charge on the system , because it wasn't complete until the dash was installed and the coach manufacturer charged the system , so I'd be very surprised if Spartan has an exact amount , because they don't know what dash system the coach builder installed .

[Rob_M]

I wouldn’t cancel a trip because dash air isn’t working. Run the generator and roof ac(‘s) and use a fan to push the cold air to the front if necessary. Fix the dash ac when you return.

[Ray,IN]

This might be useful: Heavy duty truck air conditioning service manual.
It also addresses MH's.

[Genevatexan]

Our Genset is old faithful and so far has never uttered a peep, so using a fan to push the front cabin AC toward the cab is a good plan. thanks.
I'll also review the heavy duty truck AC manual now. Thanks, Ray.
No progress over the weekend since they closed up on Saturday afternoon. I'll reach out to Spartan first thing monday to understand the cooling design. What I hope is that the Hydraulic clutch that controls cooling for the engine radiator is fine, and a lessor clutch is installed on the Condenser radiator. But a quick summary from Spartan on a similar Newmar 40ft coach from 2007 says the MountainMaster GT Chassis uses a "1,326 sq. in AKG parallel air flow system with low profile radiator, Charge Air cooler, hydraulic oil cooler, and integrated AC condenser with Modulated Hydraulically driven cooling fan. " With the coach 30 miles away in a shop I can't get under it and look at that setup and see what the shop says is wrong. My Spartan Manual is also in the coach. The shop lead told us Friday that he can "stop the cooling fan with his hand", but is that the engine cooling fan that doubles as the condenser fan, or is there another cooling fan? The engine has never run over about 185F and that's under heavy load. It will cool to 149F pretty quick when coasting or at idle after a tough run, so I don't think the hydraulically operated engine cooling fan is an issue. I will get up there tomorrow at the end of the work day and get under it and see what we are talking about.

[Rob_M]

Originally Posted by Genevatexan

Our Genset is old faithful and so far has never uttered a peep, so using a fan to push the front cabin AC toward the cab is a good plan. thanks.

We have this one which moves a bunch of air. Really handy to have on the coach.

Lasko U12104 High Velocity Pro Pivoting Utility Fan for Cooling, Ventilating, Exhausting and Drying at Home, Job Site and Work Shop, Black 12104 12.2 x 9.6 x 12.3 inches https://a.co/d/7fAcDjg

[Genevatexan]

Thanks Rob, we are still peeling the onion with this shop. For those who are interested, our 2007 American Coach is on a Spartan MountainMaster chassis. This version uses the hydraulic engine cooling fan to cool the engine radiator, AND the AC Condenser. With a new compressor and charge, we are now seeing that the cooling fan is not triggering when pressure (heat) starts rising on the high side of the freon system. This trigger will send a command either to the ECM or direct to the Electric Solenoid Valve (Spartan Part #1709-FF1-803001 - $360.56) which in turn will raise the pressure to the hydraulic cooling fan, even though the engine itself has not demanded it. The demand comes from a pressure switch that we can't find. there is a low pressure switch (low on freon) and a high pressure switch (shut off compressor, pressure is too high -around 350F), but the switch we need is the trigger to set that fan working to cool down the condenser. It likely triggers above the low pressure switch and before the high pressure shutoff. Anyone know this part # and location? the only schematic on Spartan MountainMaster on line is to fuzzy to use.

[vito.a]

On legacy Monaco and Country coaches the hydraulic cooling fan is controlled by the Cummins engine ECU sending a signal to the Sauer Danfoss electronic over hydraulic fan controller. Unfortunately, the Sauer Danfoss controllers have a high tendency to fail.

Some of us have replaced it with a mechanical wax valve that then controls the hydraulic fan mechanically based on coolant temperature. Caterpillar and Detroit diesel engines came factory equipped with Sauer Danfoss mechanical wax valves but most Cummins engines use the electronic controllers.

This is a link to a thread on replacing the electronic controller with mechanical wax valve.
https://www.irv2.com/forums/f115/fan...376611-10.html

Attached is a picture of the Sauer Danfoss electronic fan control module.

For what it's worth most of our large diesel coaches use 4# of R134a and we use a large electric cooling fan on the condenser when charging.
Hope this helps.

[timjet]

On my '07 Tradition 40Z the AC condenser is part of the radiator stack. Specifically it is the bottom radiator of the stack. My Cummins ISL, 400 HP coolant typically runs at 180 F but never below 175 after warmed up. You may have an issue if as you mentioned your coolant temp drops to 145 after the engine has warmed up. I however can't speak to coolant temps if you are operating in a very cold environment.

The speed of the hydraulically operated fan is governed by the ECM and by the rotation speed of the engine. You should never be able to stop the fan with your hand, even at idle. I believe at idle my fan turns at about 400 rpm, fast enough to do major damage to your hand.

I have put about 6-7 lbs of R134 into my dash air. I am only able to get 135 psi on the high side after charging with refrigerant but that seems to be enough to get roughly 55 deg air out of the air outlets. I should be getting lower temps though the outlets but 55 seems to cool enough.
Seltec is the same compressor Spartan will sell you but it may be branded with a different name. You will pay much more for the same compressor from Spartan.

The compressor has a clutch on it that engages when pressure is low. It will not engage if you have 0 pressure and or no refrigerant in the system to protect the compressor. I believe it kicks on at about 30 psi but am not sure. So you may need to charge with a pound or two before the clutch engages.

If you have opened the system by replacing the compressor you need to vacuum the system before you charge. Some say you need to flush as well.

I would suggest you go to a AC shop that does motorhomes but any good AC shop should be able to fix your system.

However you should learn how to vacuum and charge your dash air yourself. Dash air on motorhomes need constant attention and you will over time pay a bundle to a shop unless you do it yourself.

[timjet]

Another thought, you can force your radiator fan to operate at it's highest speed by disconnecting the electrical connection to the fan motor. This is a fail safe measure to prevent overheating. The fan is still dependent on engine speed, thus at idle it will not be running at it's highest speed because the engine hyd pump is not putting out its max pressure.

[Genevatexan]

Vito and timjet, thanks.
This rings true for everything I have learned. I can confirm now that the condenser is part of the cooling stack and was built by Spartan. Rev Group's diagram only goes to the expansion valve. The instruction from the ECM also sounds correct, and the only deviation is that there is an Electric Solenoid valve but the 3 x 3 fan controller box was not built on this model, Just the electric solenoid valve on the hydraulic feed. And yes there is a low pressure switch to protect the compressor and a high pressure switch to cut it off to protect the overall system. I think there are two issues from your input: 1) lack of signal coming to the solenoid valve and the fact that the fan can be stopped. The ECM has to get the information from somewhere to tell the fan to speed up, and the source of that command is my next question. I think I saw a drawing somewhere online that says that switch is at the evaporator, or somewhere on the hydraulic circuit to read the increasing pressure on the line before it hits the high limit switch. thoughts?

[vito.a]

With the dash A/C off, the engine ECU uses coolant temp as the primary input to control fan speed. When you switch the dash A/C on, there is an additional input signal that controls minimum fan speed. This input usually runs the fan at a minimum speed to cool the condenser. It can be overridden by high coolant temp.

If you decide the electronic controls are not working correctly, you can investigate the manual conversion kit from Source engineering.
Source Engineering Inc | Custom RV Chassis | Eugene, OR

[Rob_M]

I didn’t read the thread again but I think you were looking for a high-pressure switch? I found one driver side front compartment I believe. Of course mine is a completely different year model.

[bpu699]

You don’t need to know an exact refrigerant amount. You load it up until it reaches the desired pressures. Start low, and add until you get the correct readings.