A/C Woes

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skizot722

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OK, so we're in the middle of a heatwave and I don't think my A/C is doing a good enough job. Today when I was driving home it was 99 outside, and my car was probably a good 120 when I got in. I have a good 15 minute drive, and it was still friggin' hot in it when I got home. I found an excerpt from the shop manual about measuring the output temperature, so this is what I did, and the temperatures I recorded.

Outdoor air temperature during test: 99.1 *F

1. Put the car in Park, and turned the heat on to 90 *F for both sides, on highest blower setting, with recirculate on. I let that run for 5 minutes.

2. After the 5 minutes, I measured the cabin dry bulb. It was 134.3 *F

3. I put the A/C on 60 *F for both sides, highest blower setting, with recirculate on. I let that run for 5 minutes.

4. After that 5 minutes, I measured 99.4 *F cabin temperature. The passenger-side vent was blowing 91.9 *F air, and the driver-side was blowing 77.4 *F air.

According to what I read, I should have been seeing about 45 *F air coming from the driver-side vents. I know there is a 14.5 *F difference between driver-side and passenger-side output temperatures, but 77.4 is still much higher than 45 *F. I would think that with the output temperature being that far off, the charge would be low enough to cause a CEL, or blow a fuse, right?

Any ideas/help is greatly appreciated - it's hot a sh!t out right now.
 
I just had a similar issue, I changed the DCCV and added 18oz of r134a and it's now cold. But I didn't buy enough refrigerant as the pressure was still not where it should have been.

I think another 6-10 oz woulda topped me off.

But it is now alot better than what it was... Which was basically all uncooled air and heat on the passenger.
 
That sucks! I have A/C woes as well. I found out that the expansion valve on the evaporator is clogged on my car somehow. It's a $23 dollar part but requires the dash to be pulled out to fix it! :slam
 
No code is triggered for low refrigerant level.
If you want to do it right, Harbor Freight has a gauge set for $50. You compare the high and low pressures versus the temperature add R134 if the readings are below the normal range.
 
Subzero makes a kit with a reusable gauge and hose for like $35 (@Autozone). It also comes with that 18oz of refrigerant I mentioned.

Not sure how much refrigerant is needed to get it to that listed 45F air, but it seems like I was getting close to the correct pressure and my air is definitely not 45.
 
Andrizzle said:
Subzero makes a kit with a reusable gauge and hose for like $35 (@Autozone). It also comes with that 18oz of refrigerant I mentioned.

Not sure how much refrigerant is needed to get it to that listed 45F air, but it seems like I was getting close to the correct pressure and my air is definitely not 45.
Click to expand...

The problem is that you can't really do it correctly with just a low side reading. You need the high pressure reading too. For example, you might have a bad expansion valve instead of low refrigerant. Without the high side reading, you won't know that and you will overfill it and cause more problems.
 
Agreed...it should be done by someone who has hvac experience.
 
joegr said:
The problem is that you can't really do it correctly with just a low side reading. You need the high pressure reading too. For example, you might have a bad expansion valve instead of low refrigerant. Without the high side reading, you won't know that and you will overfill it and cause more problems.
Click to expand...

+1

The high pressure side is actually more important then the low pressure side. Either spend the money on a guage set or take it to any number of places. It's summer, they will all be climbing over themselves to give you a free diagnosis and try to sell you stuff. Even the Ford/Lincoln dealer probably has a free/cheap special going on it.
 
I'm having issues as well I have to replace my ac clutch. Buy your situation seems to be both the dccv and possible low refrigerant try to get your system tested and recharge and if its full then have them troubleshoot if the ac components all check out good then its the dccv.
 
So none of the auto parts stores here rent the r134a manifold gauges. I ended up getting one of the recharge cans that hooks to the low side port. It was 95 *F outside, and the low side pressure was 30 psi. According to the shop manual and recharge can instructions, it should have been between 50 - 55 psi. So I started adding some. I added a little and waited, and continued this a few more times checking the gauge. The low side pressure would go up a little, but it eventually went back down to 30 psi. I had a friend go inside the car and hold it steady at 1500 RPM, and the low side dropped down to around 20 psi. In the process I ended up adding about 7 ounces of r134a.

I really wish they rented the r134a manifold gauges, because I needed to be able to see what the high side was doing as I was adding the refrigerant. They sold them there, but they were $90.

I did measure the output from the vents, and it was a *lot* colder. I measured around 37 *F driving around, with the fan on medium (3 marks, and the passenger side only differed by about 1 degree). However, it sounds like there's something still wrong with the system. Any MVAC experts out there care to chime in?

I really hate taking my car to any shop, and I always prefer to do the work myself, even if it costs me a little more in time and/or money than taking it to the shop.
 
skizot722 said:
I really hate taking my car to any shop, and I always prefer to do the work myself, even if it costs me a little more in time and/or money than taking it to the shop.
Click to expand...

Me too. However, one of the things I've learned in my 54 years is that sometimes it's best to let the professionals handle the situation. In this case, they have all the tools and expertise to fix this. Probably cheaper (in the long run) and definitely with less frustration. Life is too short......
 
It's quite possible that your system needs more than 11 oz of refrigerant. It takes about 28oz refrigerant + 7 oz of oil. However, you can't know for sure without the high pressure gauge.
Anyway, if it needs that much, you need to go to a dealer or a good AC shop and have the leak found, system purged, and the right amount of oil and refrigerant put back in.
 
LS4me said:
Me too. However, one of the things I've learned in my 54 years is that sometimes it's best to let the professionals handle the situation. In this case, they have all the tools and expertise to fix this. Probably cheaper (in the long run) and definitely with less frustration. Life is too short......
Click to expand...

Yeah, I've just been burnt in the past by "professionals". Speaking of the problems I've had, and A/C, it took 3 different companies to fix my residential A/C system. The TXV was bad on it, and finally the second tech from the third company that came out found the problem. That cost me both time and money when the first company should have been able to find the problem easily, if they knew what they were doing. Unfortunately, not all professionals are real professionals.

I'm also extremely particular about my car, and I just read a thread on here the other week about an LS owner that had their car damaged when they took it into the dealership (and the dealer finally agreeing to fix it, but using bondo). That type of crap makes me paranoid to ever take my car to a shop/dealership. The truth is, the majority of people just don't care about other people's property.

I guess my question now is, if it continues to blow low- and sub-40s, and the compressor is not shutting off due to the high pressure switch, should I even bother taking it into the shop? I understand being too low on freon can damage the compressor due to the lack of oil, but if it were that low, there's no way I'd be seeing the outlet temperatures I'm seeing.
 
It's all up to you. I think that the risk of doing more damage is low, but not zero. Of course, the risk of a shop doing more damage is not zero either.

Feel the underside of the compressor. If it is dry, then I think you can feel pretty good. If it is wet with oil, then you probably have lost most of your compressor oil.
 
skizot722 said:
According to the shop manual and recharge can instructions, it should have been between 50 - 55 psi. So I started adding some. .
Click to expand...

A P/T chart for 134A gives 50-55 PSIG as saturation vapor pressures for 54-58 degrees. 30-35 PSIG are vapor pressures for 35 to 40 degrees.

Angel eyes can interpret this for you.
 
azeo410 said:
A P/T chart for 134A gives 50-55 PSIG as saturation vapor pressures for 54-58 degrees. 30-35 PSIG are vapor pressures for 35 to 40 degrees.

Angel eyes can interpret this for you.
Click to expand...

Here's the chart for the LS, which has a variable displacement compressor and the thermostatic expansion valve.

http://deneau.info/ls/s6x~us~en~file=s6xc0006.htm~gen~ref.htm

Note that 45 to 80 PSI is the expected low side pressure for an exterior temperature of 100 F (30 to 60% humidity).
 
joegr said:
Here's the chart for the LS, which has a variable displacement compressor and the thermostatic expansion valve.

http://deneau.info/ls/s6x~us~en~file=s6xc0006.htm~gen~ref.htm

Note that 45 to 80 PSI is the expected low side pressure for an exterior temperature of 100 F (30 to 60% humidity).
Click to expand...

You definitely want to be on the low side of that band as much as possible...80PSI is getting pretty high for the suction side.
 
I looked at those charts again, and the one for 100 *F - 120 *F says 30 psi to 50 psi is acceptable for 100 *F. I think the first chart may be a little misleading, because it's trying to compensate for such a large humidity range. At 100 *F the difference between 30% humidity and 60% humidity is huge.

I understand that you want the suction line pressure to be as close to 30 psi as possible without being under it. I just need to know what the high side looks like to make sure I'm not overcharging it. I've got a friend with some r22 gauges and car adapters, so I'm going to take a look at both high and low side pressures this weekend.
 
Can you fill the system and check the high side intermittently? The low side pressure gauge should work for the high side also? Correct?

I am thinking of adding a bit more refrigerant to mine, but only have one gauge/hose.
 
Andrizzle said:
Can you fill the system and check the high side intermittently? The low side pressure gauge should work for the high side also? Correct?
Click to expand...
Nope. The high side schrader valve is smaller in diameter. The fitting that comes with the recharge bottle is the larger diameter for the low side, and the gauge also only goes up to 80 psi, iirc.
 
Andrizzle said:
The low side pressure gauge should work for the high side also? Correct?
Click to expand...

No, the fittings are different sizes. Also the gauge needs to have the right scale on it...a low pressure gauge will not read the high pressures, and a high pressure gauge will not have the needed resolution for low pressures.
 
Ah. Damn. I guess they did that to prevent people filling the high side?

Thanke for the info.
 
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