[Buford_T_Justice]

OK! just removed blower motor and used an inspection mirror...

Most of the evap is clear... but there are a few COMPLETELY clogged sections...problem found! (Thnx RT). now.. can I thoroughly clean it any other way than reaching through that little hole? It looks like I can remove a large plastic section below and to the right of where the MAP sensor would be on a diesel.... It's black and has a heat shield on it due to its close proximity to the engine.. It looks like the other side of the evap. Is it possible to take that off?

 

[RT]

You might be able to get the back cover off - then you could use compressed air to blow the crap out - maybe while running a shop vac at the blower hole to catch any flying debris.

Don't forget to verify the blend door is moving. You can pull your glove box liner and watch the lever move while you move the controls.

Here's a picture of the evaporator cover screws and what you will see when its removed:

View attachment evaporator.pdf

 

[Buford_T_Justice]

OK..
After about 5 hrs, I removed the evap cover, cleaned the evaporator for about an hour, running the the compressed air up and down each row. I used alcohol to help clean it. I visibly removed a bunch of junk. I put it back together, TRIPLE checking the seal ALL the way around.

Ambient temp = 95, Im now getting 69F (was 60-65) out of the vents after letting the vehicle run for 40 mins. My low pressure line is still cold and sweating. Compressor is still running well. The blend door is also switching when needed.

Included is a picture of the evaporator cover after reassembly, and a pic of my r134can gauge (I dont have manifold gauges) on the low side.

 

[RT]

Whoa, whoa - is that your low side pressure? You are WAY overcharged. Any refrigerant has a pressure temperature curve. For fixed orifice systems, especially with short piping (unlike the huge runs in some houses) you can assume your low side pressure and its corresponding temperature equivalent are roughly equal. R134a has a pressure temperature equivalent of 65.71° at 65 psi. That means that if your low side is showing 65 psi - the best you could ever hope for out of the evaporator is 65.71° - check here for a chart: R134a Refrigerant Pressure Temperature Calculator

If you get your low side pressure down to around 32-34 psi, you will have an evaporator temperature of about 36-38° - much more enjoyable temperatures.

Have you had the system open? Was it completely vacuumed down before being recharged? I sure wish you were close enough for me to run over and put a full set of gauges on it for you.

 

[Buford_T_Justice]

System has not been opened that I know of.

Here's what the "Professionals" have told my mother:
-You need a new compressor please give us $1400
-with high ambient temps such as above 90F, a charge of 40-50 is fine........

sounded high to me too, thats why I put that pic up. Thnx so much

Im in woodlands area/north Houston btw.

 

[RT]

That's just down the road - I'm in the Lake Conroe area. Dump the pressure down to 35psi or so. If that doesn't fix it, we can make a time to meet somewhere on I45 and I'll bring my gauges.

 

[Buford_T_Justice]

Awesome, Will do

 

[Buford_T_Justice]

I hope Im doing something wrong....

Just dropped the pressure and as I did, my friend with me watched the digital thermometer in the vent go from 71F to 80F. I got the pressure down to 40psi and if I tried to do it any more it seemed like it would go right back up to over 40. Now, the line into the accumulator was cold, but the one coming out was hot, which of course was the input into the evap. (And it was definitely the input into the evap, the one that was cold and sweating before.)

 

[RT]

There may be a restriction. I'll PM you in a second.

 

[NAVYFLYER]

reading this I do have my manifold readings and I am in the 60 psi realm on the low side and the high side is registering zero, the ac is blowing luke cold air. Any ideas?

 

[RT]

I can see no way the high side would really be zero. Sounds like a fitting issue or gauge issue. Just for kicks, put your low side gauge on the high side with the engine off. You should show the same pressure on high and low side that way.

Can you check your suction line in the front and the one in the back (behind the right side kick panel in the cargo area) and compare the temps. With the other vehicle, I was suspecting the orifice tube was clogged and all the freon was being directed to the expansion valve in the back.

 

[NAVYFLYER]

I can see no way the high side would really be zero. Sounds like a fitting issue or gauge issue. Just for kicks, put your low side gauge on the high side with the engine off. You should show the same pressure on high and low side that way.

Can you check your suction line in the front and the one in the back (behind the right side kick panel in the cargo area) and compare the temps. With the other vehicle, I was suspecting the orifice tube was clogged and all the freon was being directed to the expansion valve in the back.

I will get on it soonest and report the results, I thought that was wierd myself on the high side but I have never messed with AC before.

Update, it was the connection on the high side. Connecting both high and low with engine off and the pressures were about the same, after letting the engine run for about three minutes and the pressure on the low side was in the 50-60 realm and the high side was about 160-180... ambient outside temp is about 85-90 at 0730.... It is blowing cold as it has in the am and the truck is cool but it takes forever to cool the truck down and it does not seem cold in the mid afternoon. I also have a F150 that it is blowing a lot cooler air in that same scenario. I recognize we have had 19 days or so of 100+ temps but it takes 10 to 15 minutes to get the temp down inside the truck so you are not sweating your butt off. I have not done the thermometer test yet but that is forthcoming. The EX is wedgewood blue I believe they call it so it is a dark color.

 

[Daves Garage]

I realize this is an old post but I wanted to see if anyone found a solution. I am having a similar issue with my 2000 Excursion 7.3, entire system is new except for the front evaporator. I do a lot of ac work but this one has me baffled. Low side pressure will not go below 50-55 psi. Ive even tried going to smaller orifice tubes and it wont drop ( I understand the system isnt designed for this, just thought I would try). I bought the truck in 2010 and its never had good ac. The only thing I can think of is maybe that the system has too much oil? I pull 29+" vacuum for 90 minutes before I charge and it holds the vacuum for an hour so I dont believe Im getting air in the system. Thank you for any help!

 

[marcusallen]

I hope Im doing something wrong....

Just dropped the pressure and as I did, my friend with me watched the digital thermometer in the vent go from 71F to 80F. I got the pressure down to 40psi and if I tried to do it any more it seemed like it would go right back up to over 40. Now, the line into the accumulator was cold, but the one coming out was hot, which of course was the input into the evap. (And it was definitely the input into the evap, the one that was cold and sweating before.)

Did you ever figure out why your ac wasn't blowing cold? My 01 Excursion 7.3 has the EXACT symptoms to a T that you describe in your thread with RT. I'm hoping you can point me in the right direction. Thanks in advance![/QUOTE]

 

[RT]

I missed the last few posts. Re-reading them along with yours shows a trend of high low side pressures without a true overcharge condition. This would point to weak reed valves in the compressor. It is harder to evaluate MVAC with respect to this because measuring subcooling and superheat is harder and less meaningful. On HVAC, you can watch those four parameters trend and diagnose just about anything.


Sent from my iPhone using Tapatalk

 

[marcusallen]

I had my system evacuated and recharge last week. At the time of charging the mechanic mentioned that both the low and high side measures appropriate psi but were flickering which he said in his experience indicates a weak valve/s in the compressor. Currently my sys is fully charged with no leaks and still only blows slightly cooler than ambient. Oddly enough I believe it blows cooler when I have the windows rolled down on a hot day. I have removed the fan blower and used compressed air and water to rinse out the evap coil. In addition, I thoroughly rinsed out the condenser which looked externally to be in good shape. While being charged with freon the lines where cold and sweating. As it is now, all lines just warm from the heat off the engine. Just past the orifice however, the line going into the evap coil is almost ice cold after only running a very short time. Last thing to note is that I changed the temp actuator only to realize the one I had was still good, regardless I installed the new one with no change in cabin temperature. Next things on my list to check after watching youtubes are the air gap on the compressor and the blend door itself.