AC too high pressure?


Granger

New member
Joined
Jan 22, 2013
Messages
20
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
this is probably posted somewhere but i can't find it.. if it is, feel free to give me the link and delete this post.

my ac is not working. durr. ac compressor engages just fine but then it gives the engine too much stress and dies. I check the pressure with a pressure gauge on the low pressure port (by the air dryer). and it is reading way to high.

Does this mean i have a bad pressure switch? and does a bad pressure switch mean i have to drain all of the freon and get it re vacuum pumped in order to get it working again?
 


Rock Auto 5% Discount Code: 248EE46702D889 Expires: October 1, 2019

adsm08

Well-known member
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
31,624
Reaction score
1,010
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
Sorry, really not trying to be a dick here, just trying to save you some aggravation and possibly some bodily harm.

It takes a certain amount of skill, knowledge, and equipment to work on A/C. From some of the things in your post I really doubt you have any of the above in the needed quantity and recommend you have a trained professional look at your air conditioning. You can, and despite being a trained professional have almost been several times, severely hurt working on air conditioning if you don't know what you are doing and don't proceed with caution.

That said, I will answer your questions.

High pressure on the low side means one of two things.

1) Your orifice tube (the piece that causes a restriction in the line and makes the low side the low side) has come apart and is no longer posing a restriction to the flow of refrigerant.

2) Something else has happened to cause a larger restriction farther down the line. It is possible that the drier has started coming apart inside and pieces are blocking the lines.


The first thing I would do is recover (you don't "drain" A/C refrigerant) the system, pull the orifice tube out and look to see if anything is wrong with it, damage, contamination, etc.


Also, as the compressor engaged did the low side pressure drop off at all? If the low side didn't drop (and this is where it would be really nice to have a high side reading to compare to) it would mean the compressor is shot.

Also, to swap out the pressure switches you do not have to have the system recovered. The switches have valves on them, just like tire valves, that keep the system sealed when the sensor is removed from the line.
 
Last edited:

Granger

New member
Joined
Jan 22, 2013
Messages
20
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
Okay, I'll just change the switch tomorrow then as a cheap test to see if that fixes it.

Thank you for your concern with my safety, I am not as knowledgable with the AC system as I have removed it on my other car and would want to take precaution when "recovering" the ac system.

You're sure that I can just remove the low pressure switch from the dryer and it wont relieve the pressure?

As for checking the pressures with the compressor engaged, I drained some of the pressure down to the appropriate level, turned on the ac for a few seconds and checked it again and it is at around 110-130psi..
 

UrbanRedneckKid

Active member
Solid Axle Swap
Joined
Aug 30, 2007
Messages
2,453
Reaction score
16
Points
38
Age
32
Location
Cass Co, Missouri
Vehicle Year
1994
Make / Model
Ford
Engine Size
4.0L
Transmission
Manual
As for checking the pressures with the compressor engaged, I drained some of the pressure down to the appropriate level, turned on the ac for a few seconds and checked it again and it is at around 110-130psi..
On the low side!!??
Go get a set of gauges, harbor freight has cheap ones. Needs high and low readings, and a service port.
Take a video of the guages, static reading then turn the A/C on, then post it here.
 

adsm08

Well-known member
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
31,624
Reaction score
1,010
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
Yes, I am sure that there is a little schreader valve under the switch that will not allow the refrigerant to come out when the switch is removed. I'd still wear gloves and glasses taking it off.

110 to 130 PSI sounds like a good static pressure if the outside temp is in the 80s or 90s.

Static pressure is what you have with the compressor off. Kinda makes me think your compressor is shot.

The thing with compressors is that they work a lot like engines. They have that same capacity for the cylinders to wear out and have no compression, and then you never get too far away from static pressures.
 

UrbanRedneckKid

Active member
Solid Axle Swap
Joined
Aug 30, 2007
Messages
2,453
Reaction score
16
Points
38
Age
32
Location
Cass Co, Missouri
Vehicle Year
1994
Make / Model
Ford
Engine Size
4.0L
Transmission
Manual
110 to 130 PSI sounds like a good static pressure if the outside temp is in the 80s or 90s.

Static pressure is what you have with the compressor off. Kinda makes me think your compressor is shot.
Exactly what I was leaning on, bit wanted the proof of the gauge readings before I said anything.

Also as adsm has been saying, the switches will come off without Freon loss, if the schrader is good.
 

Granger

New member
Joined
Jan 22, 2013
Messages
20
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
Okay, im going to change the switch since it's only $20.. And if that doesnt fix it, i'll get those gauges to show you all here..

On a side note, how much do ac repairs cost to fix at a shop? I've never taken my car or truck to a shop in 6 years. But i've also never had ac for 6 years..
 

kryptonitecb

New member
U.S. Military - Veteran
Joined
Dec 5, 2011
Messages
1,314
Reaction score
17
Points
0
Location
Fort Worth, TX
Vehicle Year
1994
Make / Model
Ford
Engine Size
4.0
Transmission
Manual
Compressor replacement is big $$$$, do it yourself it's real easy. Replace the dryer, orfice tube, and O-rings for all the above while you're at it, again it's real easy should take 2-3 hours by yourself. Then just have a shop pull a vacuum and fill with refrigerant, that should run under $200. So your looking at $500 to $600 total compared to over $1000 for a shop to do it for you.

Sent from the road while ignoring traffic
 

Granger

New member
Joined
Jan 22, 2013
Messages
20
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
Compressor's are like $200 at advance? I can do mechnical work just fine, it's things like pulling the vacuum and filling the refrigerant that i cant do... And i cant diagnose an ac problem because im never used ac before in my life. Decided i would try to fix it on this ranger for the sake of my girlfriend. Usually when i buy a car i just rip the ac system out to save room in the engine bay. It always gets in the way, but i figured since everything was still in tact when i bought the truck that i would do this one little thing for my girlfriend.. But im not gonna do it for $600, id rather rip it out and retrofit a supercharger for that price! :p
 

kryptonitecb

New member
U.S. Military - Veteran
Joined
Dec 5, 2011
Messages
1,314
Reaction score
17
Points
0
Location
Fort Worth, TX
Vehicle Year
1994
Make / Model
Ford
Engine Size
4.0
Transmission
Manual
Compressors are ~$300, superchargers run more and take more work and tools than an ac system.

Sent from the road while ignoring traffic
 

Granger

New member
Joined
Jan 22, 2013
Messages
20
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9
Transmission
Manual
I was joking. Id rather put a supercharger in cause im more familiar with that stuff, that was my point. But anyway, i bough a low pressure sensor because it was $20, ill throw that on. When nothing happens, ill go to harbor freight and get those gauges to show the difference in the high and low. That's what you guys were asking for right?
 

OLD WRENCH

New member
Joined
Jul 22, 2013
Messages
3
Reaction score
0
Points
0
Vehicle Year
1989
Make / Model
FORD
Engine Size
2.9
Transmission
Manual
Don't do your diagnosis by replacing parts!!!! If you don't know how to diagnose then take it to someone that does. You will actually save money by letting a pro check it out for you!! Old Wrench
 


Top