When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Before we get to that tho, your question about testing conditions is important, and yes I have done those Mfgr recommended configurations before. They are useful but a bit of a PITA in my opinion so I do it as stated below.
Methdology:
I did the test while driving with all windows, doors, & sunroof closed, and recirculate on. Digital Thermometer (that I have tested for accuracy) was placed in the drivers side center vent. It also records Hi/Lo temps.
I drove around "the block" which is really a general neighborhood area. 6mile trip total. This happened at night and speeds were between 35-45mph. 1500-2500 RPM
After the test I inspected and took pics of the lines, there was not much condensation noticeable on the low side lines. (even at the unusually high humidity we have now) We probably shouldn't pay too much attn to the condensation on the lines because that is dependent on many other variables.
AC Settings: (I'll put a pic below)
MAX AC Cold (60f on the dial) AUTO
Fan was on High speed
Recirculate ON
Zone was set to MONO
AC Rest light was illuminated
Conditions:
Outside Temp: 89F
Car Dash Temp Indication: 85F
Outside Humidity: 38%
Length of trip: 6miles (~ 8-9 minutes)
Car had been sitting in garage and temp had normalized before the test. This made the Auto setting ramp up the fan to High.
Results:
When I looked at the thermometer, it was usually between 41-44F but it did record the lowest achieved temp as 38.8F.
The time it took the car to get into the low 40's was under 2 miles and less than 3min at those low speeds.
Interesting side note, after the first two miles I had to turn the vent away bc the cold air was making my face hurt.
Vehicle Info:
2008 GL450
Rear AC option
159k Miles
AC system = Original (I have nearly full records so I believe that is correct)
Last edited by justin3219; Jul 29, 2021 at 12:50 AM.
A good vacuum pump for a/c systems will pull almost complete vacuum, 29.9in/hg or lower. With this, 30-40min is sufficient, I often set the machine for an hour just to be safe. It will fully boil off any moisture at that pressure at ambient temp, so the system will be fully dry, which is what you are hoping to accomplish.
This has been my experience as well. ~40minutes even with a fairly cheap, single stage vacuum pump has pulled down my vehicle AC systems enough to give good performance.
Before we get to that tho, your question about testing conditions is important, and yes I have done those Mfgr recommended configurations before. They are useful but a bit of a PITA in my opinion so I do it as stated below.
Methdology:
I did the test while driving with all windows, doors, & sunroof closed, and recirculate on. Digital Thermometer (that I have tested for accuracy) was placed in the drivers side center vent. It also records Hi/Lo temps.
I drove around "the block" which is really a general neighborhood area. 6mile trip total. This happened at night and speeds were between 35-45mph. 1500-2500 RPM
After the test I inspected and took pics of the lines, there was not much condensation noticeable on the low side lines. (even at the unusually high humidity we have now) We probably shouldn't pay too much attn to the condensation on the lines because that is dependent on many other variables.
AC Settings: (I'll put a pic below)
MAX AC Cold (60f on the dial) AUTO
Fan was on High speed
Recirculate ON
Zone was set to MONO
AC Rest light was illuminated
Conditions:
Outside Temp: 89F
Car Dash Temp Indication: 85F
Outside Humidity: 38%
Length of trip: 6miles (~ 8-9 minutes)
Car had been sitting in garage and temp had normalized before the test. This made the Auto setting ramp up the fan to High.
Results:
When I looked at the thermometer, it was usually between 41-44F but it did record the lowest achieved temp as 38.8F.
The time it took the car to get into the low 40's was under 2 miles and less than 3min at those low speeds.
Interesting side note, after the first two miles I had to turn the vent away bc the cold air was making my face hurt.
Vehicle Info:
2008 GL450
Rear AC option
159k Miles
AC system = Original (I have nearly full records so I believe that is correct)
Great Info man!! Thanks so much for taking the time to do that for me. I ordered a good thermometer, will be in tomorrow. I will run the same test you did and post results as well.
My wife drove the car around town for a while yesterday running errands, and she said the AC was working great. She had no complaints.
When I got home yesterday from work, I started the car and ran the AC full out. This time the Low pressure line got cold and a little sweaty. So that is a good sign.
My pleasure!
Cheap digital thermometers do work great. I think I got mine on Amazon during a sale for a buck or two each. (Regularly $5-6)
Just test them in a glass of ice water and then a cup of boiling water. Mine reads +/- 1 deg F in each so that's close enough for me.
My pleasure!
Cheap digital thermometers do work great. I think I got mine on Amazon during a sale for a buck or two each. (Regularly $5-6)
Just test them in a glass of ice water and then a cup of boiling water. Mine reads +/- 1 deg F in each so that's close enough for me.
Quick update, I did a quick test with the Car just sitting in the garage, with AC running full blast. Center vent was reading 42 degrees. I will get more readings on it when I have time to take it out on the road.
Congratulations on a successful repair!
What are you doing with your old compressor?
Might be able to take out that RCV, test it with 12v like I've seen people do on YouTube, and if it seems like that was the actual problem, then maybe you could keep the compressor as a backup w/a note to replace the valve. IDK
Congratulations on a successful repair!
What are you doing with your old compressor?
Might be able to take out that RCV, test it with 12v like I've seen people do on YouTube, and if it seems like that was the actual problem, then maybe you could keep the compressor as a backup w/a note to replace the valve. IDK
It's the RCV, it always is, unless the compressor is locked up. IF you keep it, make sure it's sealed up well, they normally ship full of oil and vacuumed down, if it sits with moisture inside it at all, even from ambient humidity, it will likely be trash in a few months if you try to use it.
It's the RCV, it always is, unless the compressor is locked up. IF you keep it, make sure it's sealed up well, they normally ship full of oil and vacuumed down, if it sits with moisture inside it at all, even from ambient humidity, it will likely be trash in a few months if you try to use it.
These seem like good recommendations from ItalianJoe1. My experience has been a little more forgiving. I have personally used old compressors that were not sucked down, still had some seemingly old oil left in them, and were merely wrapped up in food grade plastic wrap, and -for me- they performed well for years!
It does make sense to seal them up as well as possible for storage if you have the ability, but if you don't, might not necessarily be the end...
Anyway, its always great to have a nice usable (perhaps OEM) part on hand that can be made ready to reuse with a simple RCV swap! Maybe you'll be able to help a GL buddy out one day!
Your low is not low enough, high is not high enough, meaning very little compressor activity. Considering there is no change between ac on/off, I'd wager your RCV is stuck in an almost closed position. With the gauges on, give it a couple sharp revs, see if it suddenly starts pumping (low drops to 35ish, high goes to 180ish), this is 100% indicative of a sticking valve. The pressures should be equal when "off", and yours aren't, looks like 70/120, which is a little pumping action but nowhere near enough to cool down the system.
This is exactly the readings my gauges are showing (70/110) after car has been running with warm air blowing. My AC will work 100% one day and the next may only blow warm air. I can sometimes get it to unseat by slightly venting the High side with my gauges connected and the car off. Once I restart the vehicle it will kick back open and pressure readings will go to ~30/150 or so.
My compressor was replaced 6 years ago and 40k miles. I am wanting to try the compressor control valve. My question is, when I get the system evacuated and replace the valve, should I also replace the dryer and how much oil will need to be added?
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
