Need Help With Dash A/C Problem .....

Topic: Need Help With Dash A/C Problem ..... (Read 3478 times) previous topic - next topic

Re: Need Help With Dash A/C Problem .....

Reply #25 – September 01, 2014, 10:31:35 pm

Update on my dash A/C. I had it working, but I still felt it wasn't working as well as it should. The pressures were a little off and it would still cycle even on high (the thermostat switch that sensors air right after the evaporator was controlling the cycling).

A few weeks ago I blew the high pressure A/C line going from the compressor to the condenser. The hose failed right near the turbo. An 8 inch section of hose was very stiff and brittle from the turbo heat! I replaced the hose, put a heat sleeve over both of them, and made a redneck homemade turbo blanket from a turbo blanket kit. I'm going to wrap the exhaust manifold and the downpipe, but it was just too dang hot out. Keeping the radiant heat from the turbo away from everything in the engine compartment will be good enough for now.

I pulled the busted hose and took it to a hose expert--that's all he does is make any type of pipe/hose you can imagine. $55 for the new hose (most of the cost was the 12 feet of hose). A/C hose is unique, but it just uses barb fittings on the end.

Anyway, since I had the system open and exposed to air so long, I figured I may as well replace the reciever/drier and while I'm in there, replace the TXV (what's another $40?) and replace the thermostat (just in case it's faulty). Also, I wanted to pull the TXV out to ensure it wasn't clogged, as this will cause lower temperatures and some of the pressure indications I was seeing.

Somebody on my coach modified the wiring and put a combination high/low pressure switch on the receiver drier and disconnected the lower pressure switch on the low side. I will eventually hook the low pressure switch back up, but it's not as important as the high pressure switch for protection.

Anyway, attached are the pictures. It took me a while to find the thermostat switch--I ended up following the wire from the switch on the dash. It was in a spot that I just couldn't see it when I was looking around. I was able to reach everything without removing the doghouse, but I also used to stand on my head and work on boats. Lots of it was done by feel. All new orings were used.

When I pulled the TXV apart, my suspicions were confirmed: a blockage of desicant balls (about 6-10). I blew out the line backwards with dry air, but I wanted to make sure none were stuck in oil. My dad caught about 5 when I did my first air blow. I then flushed the line with Acetone (A/C flushing fluid will draw debates from all over the internet...acetone evaporates fast and leave little residue). To fully flush all the liquid out required me holding my finger over the discharge of the line and allow air pressure to build up and then releasing it.

Blew all the other lines out. Purged with nitrogen, hooked everything up and hooked up the filter/drier last (leave caps on it until ready to install), sucked in ~8oz of oil, and then purged system with nitrogen again, pulled a vacuum for a few hours, purged with gas, pulled vacuum, purged, pulled vacuum for 6 hours and filled up system with 5.5lbs (it seemed to be what made the pressures work the best).

Results?!!? On a super hot humid day, using outside air, the discharge temp at the vent was 60deg and the A/C didn't cycle. When I went to inside air and the sun went down, it would cycle on low fan, and as the inside cooled off, cycle very slowly on high fan (45-60seconds on, 1-2 min off). Discharge temp on high was in mid 50's +/- (I think). The thermostat is probably set around 47F.

So, that's that. The problem with A/C systems is not that they are complicated, it's just that the details matter. All this work took me quite a few hours to do correctly. Hopefully I don't have a leak and it doesn't work when I go to take my trip this week! haha

NOTE: TXV is on right side of air handler below two duct lines. Thermostat is on front of air handler forward/below the 8 ducts going toward the front of the RV.

Parts ordered from places above in thread.

Re: Need Help With Dash A/C Problem .....

Reply #26 – September 01, 2014, 10:38:32 pm

Heat sleeve: I used this because I had the system open and could take both lines off the compressor

Amazon.com: Thermo-Tec 14025 3', 2 1/2" I.D. Thermo-Sleeve: Automotive

However, this one has velcro that splits down the middle:

Amazon.com: Thermo-Tec 14035 3', 1"- 1 1/2" I.D. Express Sleeve: Automotive

The turbo now has this on it:
Amazon.com: Thermotec 15002 Turbo Wrap Turbo Accessories: Automotive

And this is going to go around the manifold eventually: Amazon.com: Thermo-Tec 14004 Header Manifold Blanket for 4 Cylinder and Straight

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Need Help With Dash A/C Problem .....

Reply #27 – September 02, 2014, 09:07:40 am

You have done well-- after $3000 spent at Foretravel, my dash air still doesn't work properly. I'm about to tear into removing the evaporator to change out the fan. That is the issue now, not moving enough air. Due to having to dismantle the dash to access it, they quoted 10 hours labor, so I pulled the plug-- have to do it myself. I had the same issue, dissacant bag in the dryer failed stopped up everything. Expansion valve replaced, condenser fan replaced, compressor replaced, receiver / dryer changed, system flushed 3 times and vacuumed, then charged. The evaporator temp is still to high, so back to the drawing board. No fault of Foretravel, just a lot wrong with the system!

Re: Need Help With Dash A/C Problem .....

Reply #28 – September 02, 2014, 11:19:58 am

I replaced evaporator, evaporator blower, expansion valve, compressor, dryer, and even the hoses before I was able to get my 1996 to blow as cold as I wanted it. Determining subcooling and superheat and adjusting the freon accordingly, I was finally able to freeze my knees. When Foretravel services freon, as soon as the evaporator outlet reaches anywhere close to 20 degrees below ambient, they stop adding freon. Consequently, they never achieve maximum cooling.

Re: Need Help With Dash A/C Problem .....

Reply #29 – September 02, 2014, 11:52:13 am

The amount of charge is not that critical in this system because it has a TXV. If the TXV (thermal expansion valve) is working correctly, it will maintain a pre-designed superheat. Sub-cool would be the only way to really determine a proper charge.

The conceptual goal is to have enough refrigerant to have a solid flow of liquid to the TXV and also have enough charge to return some cool gas back to the compressor for cooling (refrigerant cools the compressor).

Newer vehicles have variable displacement compressors--and this requires pretty much charging just by weight.

Fixed orfice are pretty easy: charge till the return line to the compressor is cool (monitor pressures). Just take note of conditions to prevent over/undercharge.

In the end, it's part science, part art/gut.

Re: Need Help With Dash A/C Problem .....

Reply #30 – September 02, 2014, 02:19:56 pm

I agree you don't need to worry about superheat with a good TXV, but when we couldn't get the air cool enough we started measuring line temperatures. We found that at idle everything was fie, but at 1500 there was a greater than 10 degree difference between front and back. We changed the lines and corrected the temperature drop and found our TXV was not operating perfectly. Installed new TXV and now we can get outlet temps in the 40's at highway speeds. I love it. The boss covers up with a blanket.

Re: Need Help With Dash A/C Problem .....

Reply #31 – September 02, 2014, 04:23:07 pm

This is really good info, I have exactly the same issue, blows pretty cold at idle, but warms as rpm increases. I have changed the heater valve as well, it was through leaking hot coolant and bucking the AC. Still not as it should be.

Re: Need Help With Dash A/C Problem .....

Reply #32 – September 02, 2014, 08:58:02 pm

Check to make sure you don't have massive air leaks in the front of the coach.

Re: Need Help With Dash A/C Problem .....

Reply #33 – September 02, 2014, 11:43:37 pm

What are your high and low pressures?

Re: Need Help With Dash A/C Problem .....

Reply #34 – September 03, 2014, 09:39:53 am

We have found no air leaks, and we have looked. I'm going to check the pressures today. I haven't done that since Foretravel charged the system. I suspect that you are correct and that the system is under charged. I'll post what I find later this morning. I really appreciate the advice here--- my "from Canada" wife won't go far in the coach with no dash AC. Right now it won't keep you knee cap cool. Really disappointing after spending so much to get it going.

Re: Need Help With Dash A/C Problem .....

Reply #35 – September 03, 2014, 10:58:28 am

That's what the generator is for, to be used if dash air is not doing the job. Many do it every day.

Run gen, run both roof air to cool coach and load generator, use table fan on floor to blow on pilot and co-pilot. Generator is happy it is being used and humans are happy to have cool kneecaps.

Re: Need Help With Dash A/C Problem .....

Reply #36 – September 03, 2014, 11:02:44 am

Agree with everything Krush said. I've had to replace everything that he did (except for the broken line) to get my AC up and running again, including having the drier pellets in the line.

On mine, the plastic fan cover that sits right up against the interior front of the RV was broken in a couple of spots. I was able to mostly fix it with some sheet metal and aluminized HVAC tape. The plastic shards from the broken cover were stopping the louvers from fulling opening and had also clogged up the fan a bit, resulting in low air flow. Once the broken plastic was removed my blower fan was able to move a lot of air. This will require removal of the doghouse to access all of this which isn't too bad once you realize where the screws are.

Re: Need Help With Dash A/C Problem .....

Reply #37 – September 03, 2014, 12:12:41 pm

Well, I just got done checking the pressures--- ambient temp 86 degrees. Foretravel had charged the system and the pressures I read at idle (700 rpm) are 20 psi suction side and 110 psi high side. With my limited AC knowledge, this seems low for 86 degree ambient. I Increased the charge to 45 psi low side and 130 psi high side ( at this ambient I believe the low side should be between 45 and 55 psi, advise if I'm wrong). Evaporator air temp was not improved much, running 78 degrees.
With inside coach temp of 83.

I believe that my fan has the same issue, it doesn't sound right and is not moving much air--- the sound would make me think of an open blower blade.
Did you have to remove AC lines to remove the evaporator?

Re: Need Help With Dash A/C Problem .....

Reply #38 – September 03, 2014, 01:01:41 pm

Quote from: Kemahjohn – September 03, 2014, 12:12:41 pm

Well, I just got done checking the pressures--- ambient temp 86 degrees. Foretravel had charged the system and the pressures I read at idle (700 rpm) are 20 psi suction side and 110 psi high side. With my limited AC knowledge, this seems low for 86 degree ambient. I Increased the charge to 45 psi low side and 130 psi high side ( at this ambient I believe the low side should be between 45 and 55 psi, advise if I'm wrong). Evaporator air temp was not improved much, running 78 degrees.
With inside coach temp of 83.

I believe that my fan has the same issue, it doesn't sound right and is not moving much air--- the sound would make me think of an open blower blade.
Did you have to remove AC lines to remove the evaporator?

Your pressures aren't in the right range according to the R134 charge that came with my set of gauges.

I did not remove the evaporator. With the center dash doghouse removed, I was able to reach back and remove the broken plastic from the fan area. A couple of flashlights strategically placed allowed me to see that all of the damage was on the passenger side with no damage on drivers side. I didn't have to remove any hoses and was able to cut some sheet metal that I tek screwed and taped to MOSTLY seal the cover up. It isn't perfect at this point but I had no intention of taking everything out of there (now thats a big job). When the fan is working correctly, it moves quite a bit of air.

You might also look at replacing the Bosch relay that is right behind the accelerator pedal in the dash. You can get a 5 pack of relays pretty cheap off Amazon. I know mine had quite a lot of corrosion in the engine compartment.

Amazon.com: AGT (5 Pack) 30/40 AMP Relay Harness Spdt 12V Bosch Style

Are you sure that everything else is working properly? Your condenser fan is blowing?

Here is a pretty good price on R134a also-

Amazon.com: Johnsen's (6312-12PK) R-134a A/C Refrigerant - 12 oz., (Pack of

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Need Help With Dash A/C Problem .....

Reply #39 – September 03, 2014, 01:05:19 pm

Push the cruise control switch to RES twice. That should take the engine to high idle. Recheck pressures. Where is your coach? I would come by, but I am on the way to doctor. I would like to read the temperatures of the lines coming out of the condensor and the evaporator.

Re: Need Help With Dash A/C Problem .....

Reply #40 – September 03, 2014, 01:09:16 pm

I had the problem of the broken fan cover. I had a new one mad out of fiberglass. If broken bad enough the valve can't close off outside air.

Re: Need Help With Dash A/C Problem .....

Reply #41 – September 03, 2014, 01:27:28 pm

The coach is in Kemah. I can measure the line temps and report. I did check the temps at the compressor-- by putting my hand on them. The suction line is cool to the touch, and the liquid line is warm, approaching hot. I am suspecting that the low air flow might be the biggest issue, but not sure yet. Foretravel says the doghouse must be removed, all the wiring disconnected and the refrigerant lines removed th change the evaporator fan, thus the 10 hour estimate from them.

Re: Need Help With Dash A/C Problem .....

Reply #42 – September 03, 2014, 02:49:22 pm

If the evaporator outlet isn't cold, increasing thr air flow will not help much. Your pressures are similar to what mine were when mine wasn't cooling. I ended up going through 3 TXV's till I found one that operated properly. My evaporator outlet line temps were running about 58. When everything was working it dropped to 29.

Re: Need Help With Dash A/C Problem .....

Reply #43 – September 03, 2014, 03:57:37 pm

This may be an adjustable expansion valve, not sure. About what should my pressures be when working, 45-55 low side and 225-250 high side?

Re: Need Help With Dash A/C Problem .....

Reply #44 – September 03, 2014, 05:19:41 pm

Yours shouldn't be adjustable. Yours is the same year as my older coach. It is both temperature and pressure compensated. The low side is controlled by the TXV and the high side is a function of the amount of freon. I am thinking your low side is a little high, but that is a guess. I was going to offer to come by and help (I am in Pearland), but I was just scheduled for knee replacement surgery.

Do you know the evaporator and condensor outlet temps at these pressures? At those pressures your liquid line coming out of condensor should be about 125 degrees.

Re: Need Help With Dash A/C Problem .....

Reply #45 – September 03, 2014, 07:47:37 pm

29 is too cold on evap outlet temp...it's going to freeze up. Expect to see around 175-225psi on the high side and around 20-50 on the low side. Obviously give or take a bit, dependent on many variables...haha

You're aiming for about a 20degree AIR temp drop across the evap.

Line coming back to the compressor AT the compressor should be cool and sweating (if humid out). Hi side line will be hot leaving.

Low air flow over the evaporator will cause COLDER temperatures, cycling of the thermostat (if system has one) and reduced flow/lower pressures as TXV closes. Also, make sure the sensing bulb of the TXV is getting good contact and wrapped with insulation around the discharge line.

Re: Need Help With Dash A/C Problem .....

Reply #46 – September 03, 2014, 08:25:12 pm

I agree 29 is a little low but that was with a cabin temp of about 70 and it was much better than I was getting with the other two valves which were closer to 55. Even with 29 the freeze detecting switch with the sensor between the evaporator and heater coil never shut off the compressor.

Re: Need Help With Dash A/C Problem .....

Reply #47 – September 03, 2014, 08:42:55 pm

I went back over to the coach and tried again--- more confusion. With the engine at high idle, suction pressure is now at 15psi and high side is 150psi. Evaporator air temp s 74 degrees, cabin temp 84 degrees. I forgot to take my infrared thermometer with me, so I'll get the line temps in a day or so
I'm going to have to give up on it for a few days, taking the coach up to Midland Odessa to visit my daughter.
Best wishes on the knee replacement, they can be tough. On the other Hand, a few years ago my Mom's 92 year old husband had both knees replaced at the same time, and went deer hunting 4 weeks later! I'll keep you posted as I fumble through this thing.

Re: Need Help With Dash A/C Problem .....

Reply #48 – September 06, 2014, 02:50:28 am

Today, I was looking at the alternator installation and happened to look at the A/C compressor. My dash air had not been working, but I finally discovered why. Please see attached photo. I do not know when the fan belt disappeared, but small parts of it are splattered along its flight path on the insulation pad on top and both sides. It looks like it must have disintegrated. I cannot find any evidence of further damage from the flying belt.

Trent

Re: Need Help With Dash A/C Problem .....

Reply #49 – September 06, 2014, 02:15:28 pm

Hi Trent,
If it is just the belt, you got off easy. Now if the compressor is the cause of the missing belt, it gets a little harder.
Raymond

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