Dash A/C repair front to back

[RichKimball]

Wow....what started what I thought would be simple turned into quite an ordeal. But...I did it. Bad a/c compressor for dash air. Fittings had to be cut off old compressor. New fittings had to be crimped on...try finding someone that will do that for you?! LOL....but I did....for $40 labor. (that's after I had to special order the fittings as Freightliner suction hose is oversize). Oh...and the compressor fuse was blown...took 3 days to find that!!! Under the dash, behind 2 fuse blocks...taped up in the blower wire harness in a cartridge fuse holder... smh
New condenser too and a/c system flush tools and solvents. New fitting for condenser as one destroyed thread on removal.
New filter/dryer...check valve on output clogged....weird...ended up not using. All together and vacuum down....holds well overnight 29.9inches.
Add in 8oz of PAG oil per Freightliner service manual using oil injector tool...nice to have.
Add gas....just this afternoon and now have a working dash a/c system once again. Can only get 55deg air at outlets but I'LL TAKE IT!!. This project started almost 2 months ago....and little by little getting parts...service etc etc that I needed to do it.
I heard that from all that I had to do it would have cost me about $4 grand parts/labor. I don't have an exact price list of what I have...but about $600 including compressor...vacuum pump...gauges....fittings...r134a....PAG oil etc etc.
At one point I almost gave up...but I'm happy in the end.
(for those that read this already on FB...sorry)

[MikeGee]

Nice job mevman! And you can feel good knowing you saved some $$$ and the job was done right. I need to tackle the same thing on my coach in the future.

[Vectraguy]

Do you travel and carry tools, you could really have a good side gig fixing those. :-)

[RichKimball]

Originally Posted by Vectraguy

Do you travel and carry tools, you could really have a good side gig fixing those. :-)

Thanks Vectra'....but I do it 'cause I HAVE to...not that I WANT to.

[lonfu]

First, seal up your vent door on your evap cover to the front of the coach. It does nothing but make both the heater core and AC evap coil inefficient. 2nd, check you heat core hoses, one should be cold the other warm. If both are warm replace the valve or install a 3/4" pex ball valve from home cheapo on the engine side.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

This is what I used at a fraction of the cost. Make sure where your hoses go into hour evap cover that they are sealed. Use aluminum tape and duct caulking.

You are not going to like this but you should be getting about 35 degrees at your center vent MAX AC, 100 degrees ambient, 1000rpm.

Your getting close but keep going... would you believe the surface of your AC coil should be at 10 degrees???

For next year.....R134 coolant is on the way out, not legal for new cars after 2020, there are others that work better....

[Mosco]

So you got someone to put the fittings on while the AC lines were still in the coach? I just had one of my fittings break last night and not looking forward to pulling out 39' of AC lines.

[RichKimball]

Originally Posted by Mosco

So you got someone to put the fittings on while the AC lines were still in the coach? I just had one of my fittings break last night and not looking forward to pulling out 39' of AC lines.

I did Mosco. I kept calling around to shops that advertised auto a/c repair. One of the caveats is that they have to have an area large enough to handle the parking of the RV. I had to order the fittings from Coldhose.com as the shop said they couldn't get what I needed. Coldhose had it ready to ship. They used a hand style crimp tool where we just crawled under the back of the coach. I held the new fitting in place for the correct angle and the tech crimped the line.

[RichKimball]

Originally Posted by lonfu

You are not going to like this but you should be getting about 35 degrees at your center vent MAX AC, 100 degrees ambient, 1000rpm.

Your getting close but keep going... would you believe the surface of your AC coil should be at 10 degrees???

For next year.....R134 coolant is on the way out, not legal for new cars after 2020, there are others that work better....

You are correct regarding the outlet temp. A month later it was found that the initial output would be cold but as time went by the temp would increase to warm. Apparently the balance of adding gas and PAG oil was out of wack...and the systems was overcharge. I made adjustments and now have 42deg air. I have never seen or heard of outlet temp air in the 35deg range..but won't argue.

[lonfu]

Ok, so when we got to Oregon I found that I had to turn down the blower because the air was too cold and my knees would go numb, but it would kept the front of the coach cold back to the bathroom door.

I also found that air coming out was starting to smell moldy????

So I enlarged the drain hole but couldn't get the condensation to come out of the drain hole. I had to reach inside the bottom of evaporator by taking off the passenger side beauty panel.... I didn't know it came off???....

I found that there was a piece of foam rubber glued to the inside bottom of the evaporator. This was covering the holes I was drilling as well as the original drain hole at the top of the "pitched" evaporator cover bottom. Duh.... another great Evans engineering design....

On the way home it drained perfectly and all was well with no moldy smell.... I believe it is fixed...

One more little note, If you are running your roof air and smell wet fiberglass, then replace your roof AC gasket before you get roof damage....

[Old Scout]

Good DIY write-up and lots of follow-up comments....I have done a fair amount of auto AC work over the years--mostly successful, but not always.....no formal training along the way so the "school of hard knocks" was my guide. Vintage Air Company located only a few miles away so lot of access to parts and advice! So just a few thoughts to offer:
1-never understood the differences in "claimed" air temp output at the vents?
2-ambient outside air temps impacts gas pressure but not output temps directly
3-new compressors usually come with oil so never sure how much more to add
4-proper disposing/reuse of old gas, if system is still charged, is a DIY challenge
5-proper air flow across condenser and evap. coils affect system performance
6-proper gas and oil levels affect system performance
7-know fridges and freezers get very cold but claim of 35 and 10 degree temps in an auto or RV application is hard to believe
8-Bottom-line: not sure how the 20-25 degree differential "rule" applies to all this?


Always willing to learn something new?????

[Pandion]

I bought my coach with a known broken dash air system. Just didn't know how broken. Turned out the compressor had locked up, judging by the belt rubber adhered to the pulleys. I disconnected everything and flushed every hose, the evaporator and the condenser individually. Pushed a quart of mineral spirits at a time through each part with compressed air until the output was clean for three flushes. Then followed up with acetone for three flushes to rinse out the mineral spirits. I used fresh acetone for the final flush and lots of air to evaporate the acetone. The plastic mounting flange on the heater core/evaporator housing was cracked and mounting screws had pulled through. Instead of the absurd amount of money for a plastic shell, I glued thin aluminum flashing strips to both sides of the plastic with 3M 5200 and drilled new mounting holes. New compressor, receiver/drier, and expansion valve, and new o-rings for every joint. End result was 48F air. Figured I'd saved at least $2k after parts and materials.

This past July, I was working under the front cover and happened to notice the condenser fan kick off, and when it stopped, the direction wasn't consistent with the shape of the blade. (Engineer in fluid dynamics) Crawling underneath, I found that the front-mounted fan was pulling air forward through the condenser, against the airflow when driving down the road! I didn't do a before and after temperature measurement, but getting the airflow right sure can't hurt.

Next step is to insulate the duct hoses. That should help keep air temperatures in the duct down when driving across the southwest, as well as prevent condensation in the southeast.

[lonfu]

Originally Posted by Pandion

I bought my coach with a known broken dash air system. Just didn't know how broken. Turned out the compressor had locked up, judging by the belt rubber adhered to the pulleys. I disconnected everything and flushed every hose, the evaporator and the condenser individually. Pushed a quart of mineral spirits at a time through each part with compressed air until the output was clean for three flushes. Then followed up with acetone for three flushes to rinse out the mineral spirits. I used fresh acetone for the final flush and lots of air to evaporate the acetone. The plastic mounting flange on the heater core/evaporator housing was cracked and mounting screws had pulled through. Instead of the absurd amount of money for a plastic shell, I glued thin aluminum flashing strips to both sides of the plastic with 3M 5200 and drilled new mounting holes. New compressor, receiver/drier, and expansion valve, and new o-rings for every joint. End result was 48F air. Figured I'd saved at least $2k after parts and materials.

This past July, I was working under the front cover and happened to notice the condenser fan kick off, and when it stopped, the direction wasn't consistent with the shape of the blade. (Engineer in fluid dynamics) Crawling underneath, I found that the front-mounted fan was pulling air forward through the condenser, against the airflow when driving down the road! I didn't do a before and after temperature measurement, but getting the airflow right sure can't hurt.

Next step is to insulate the duct hoses. That should help keep air temperatures in the duct down when driving across the southwest, as well as prevent condensation in the southeast.

Here is a funny.... P30 chassis with fan clutch and an factory fan in front of the AC condenser. I had to put a switch on the fan to turn it off.....

In hot weather when I would run the AC the engine temp would increase and the AC would cool only to 60. Turns out that the AC electric fan, when running, the AC was switched on, would blow air against the fan clutch and disengage the clutch, thus reducing the air flow across both the AC condensor and radiator...... Causing the engine to over heat and the AC to have higher temps. Shutting off the electric fan partially solved my cooling problem.

2nd thing was the vent door located on the fire wall about 10 inches from the radiator. The vent door would be open in all positions except MaxAC, and then would open and close to balance the temp with hot air from the front of the coach. It was introducing hot radiator air into the evaporator box. I sealed off the vent door.

ON my DP I found the exact same vent door issue.

[lonfu]

Originally Posted by Old Scout

Good DIY write-up and lots of follow-up comments....I have done a fair amount of auto AC work over the years--mostly successful, but not always.....no formal training along the way so the "school of hard knocks" was my guide. Vintage Air Company located only a few miles away so lot of access to parts and advice! So just a few thoughts to offer:
1-never understood the differences in "claimed" air temp output at the vents?
2-ambient outside air temps impacts gas pressure but not output temps directly
3-new compressors usually come with oil so never sure how much more to add
4-proper disposing/reuse of old gas, if system is still charged, is a DIY challenge
5-proper air flow across condenser and evap. coils affect system performance
6-proper gas and oil levels affect system performance
7-know fridges and freezers get very cold but claim of 35 and 10 degree temps in an auto or RV application is hard to believe
8-Bottom-line: not sure how the 20-25 degree differential "rule" applies to all this?


Always willing to learn something new?????

The 20-25 temp diff is bunk.... some AC techs need an out.... RV AC systems are poorly designed and need a lot of structural "field engineering" changes before they will work correctly after they are charged properly.

Most compressors come with the correct amount of oil in them for the system to operate correctly, the only exception is the DP where the lines are long. Then the AC "art" steps in.... Too much oil in a system is the most common mistake that causes plugged condensers.

ambient air temp VS. gas pressure is important only when trying to charge by pressure. This is guessing game/art "short cut" that shop AC techs try to use to prevent having to discharge and vac a system to save time and materials. Only accurate way to recharge is by weight of coolant.

Have to have huge amounts of air flow across the condenser, huge amounts.... The control valve or coolant jet controls the amount of coolant atomized into the evaporator coil inside the coach. IN a clean system if there is not enough air flow across the evap coil then the jet can freeze and your high pressure switch will kick the AC compressor off until it unfreezes. Engineers try to find a way to balance the input air temp to the evap to prevent this from happening by introducing hot air from vent doors. Thermal expansion valves are now used on most modern systems, they are a "variable coolant jet" with a temp sensor located on the evaporator that reduces the coolant to the evaporator if it starts to freeze up. They rarely fail.

As you have found out, too much coolant and the system won't atomize the gas into the evaporator, too little coolant and not enough gas for the compressor to make liquid. Hence the balancing.... most systems have a good starting point as to how many lbs of coolant to install. Most are accurate, some are not...... The older Evans systems are the worst.....

[lonfu]

Originally Posted by Mosco

So you got someone to put the fittings on while the AC lines were still in the coach? I just had one of my fittings break last night and not looking forward to pulling out 39' of AC lines.

you can order an AC hose crimper on amazon for about $150.