AC question
Thread Starter
|
Retired guy fixn stuff
Joined: Mar 2009
Posts: 3,221
Likes: 1,233
From: East TN
AC question
On sons 99. Cleaned the evaporator, very grubby. Replaced the resistor abd cleaned the squirrel cage. Pushing allot more air.
85* outside
57* at center vent @ idle
60* at center vent @ anything above 1000.
Low side 33 @ idle
High side 165 @ idle
Went out on 3 mile drive
Low side 33 @ idle
High side 195 @ idle
Above 1000 compressor cycling
Low pressure drops to 20.
Any ideas what could be going on ??
Thanks
Keith
85* outside
57* at center vent @ idle
60* at center vent @ anything above 1000.
Low side 33 @ idle
High side 165 @ idle
Went out on 3 mile drive
Low side 33 @ idle
High side 195 @ idle
Above 1000 compressor cycling
Low pressure drops to 20.
Any ideas what could be going on ??
Thanks
Keith
Tuned
Joined: Oct 2006
Posts: 286
Likes: 0
From: Northern Virginia
have a question about the chart posted. Do you know if it was intended for diagnosis while sitting still in a service bay or while moving down the road with air flowing over the condenser coil? If the later it may be a good idea to use a good sized fan to simulate air flow as closely as possible.
I do agree that the charge in the OP vehicle seem a bit low.
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
There's another variable to take into consideration - other than airflow: RPMs. We all know how the A/C gets colder when we step on the throttle, but seems anemic when we need it most - idling in traffic on a hot day. If one were to cry fowl and call attention to air flow while driving - remember that big fan doesn't exactly suck. Well... it does... but you know what I mean.
I just copied the chart from a refrigeration website, but I didn't dig deep into all the variables. Once I saw the pressures above 1000 RPM, I figured I had enough information to call it.
I just copied the chart from a refrigeration website, but I didn't dig deep into all the variables. Once I saw the pressures above 1000 RPM, I figured I had enough information to call it.
Thread Starter
|
Retired guy fixn stuff
Joined: Mar 2009
Posts: 3,221
Likes: 1,233
From: East TN
That's the same chart I was using.
I was thinking a little low as well but figured I had a day or two to research.
I will give it a "shot" pun intended.
I will also put the a large fan in front.
Thanks to all.
Keith
Lead Driver
Joined: Jun 2003
Posts: 8,298
Likes: 25
From: Damon (South East Texas)
Another good indicator of system charge is evaporator temperature at the inlet and outlet lines. "Feel" can be a good indicator. The two lines should be fairly close to the same temperature when fully charged. If the lower (inlet) is colder than the upper (outlet), it is low on charge. I was told by a mobile a/c tech, years ago, that a blind man could charge a R134A system. 
He was referring to this situation and, of course, that the system is working properly. The pressures are also indication of a "weak" charge.
Condenser temperature also plays a big factor in system pressures. I have repaired many a/c systems on our company dump trucks and heavy equipment simply by cleaning the condenser. In that case, the high side pressure was too high. The problem with using a shop fan is that you can reduce the condenser temperature while charging the system and end up with on overcharge in "real world" situations. The a/c system relies on its own fan and air flow. It has to be able to do that. The fan would aid in diagnosis, if you had the correct charge, but were seeing high pressures.
A good understanding of "theory of operation", and how components interact, carries a long ways in the diagnose of anything.
He was referring to this situation and, of course, that the system is working properly. The pressures are also indication of a "weak" charge.Condenser temperature also plays a big factor in system pressures. I have repaired many a/c systems on our company dump trucks and heavy equipment simply by cleaning the condenser. In that case, the high side pressure was too high. The problem with using a shop fan is that you can reduce the condenser temperature while charging the system and end up with on overcharge in "real world" situations. The a/c system relies on its own fan and air flow. It has to be able to do that. The fan would aid in diagnosis, if you had the correct charge, but were seeing high pressures.
A good understanding of "theory of operation", and how components interact, carries a long ways in the diagnose of anything.
Thread Starter
|
Retired guy fixn stuff
Joined: Mar 2009
Posts: 3,221
Likes: 1,233
From: East TN
Another good indicator of system charge is evaporator temperature at the inlet and outlet lines. "Feel" can be a good indicator. The two lines should be fairly close to the same temperature when fully charged. If the lower (inlet) is colder than the upper (outlet), it is low on charge. I was told by a mobile a/c tech, years ago, that a blind man could charge a R134A system. He was referring to this situation and, of course, that the system is working properly. The pressures are also indication of a "weak" charge.
Condenser temperature also plays a big factor in system pressures. I have repaired many a/c systems on our company dump trucks and heavy equipment simply by cleaning the condenser. In that case, the high side pressure was too high. The problem with using a shop fan is that you can reduce the condenser temperature while charging the system and end up with on overcharge in "real world" situations. The a/c system relies on its own fan and air flow. It has to be able to do that. The fan would aid in diagnosis, if you had the correct charge, but were seeing high pressures.
A good understanding of "theory of operation", and how components interact, carries a long ways in the diagnose of anything.
He was referring to this situation and, of course, that the system is working properly. The pressures are also indication of a "weak" charge.Condenser temperature also plays a big factor in system pressures. I have repaired many a/c systems on our company dump trucks and heavy equipment simply by cleaning the condenser. In that case, the high side pressure was too high. The problem with using a shop fan is that you can reduce the condenser temperature while charging the system and end up with on overcharge in "real world" situations. The a/c system relies on its own fan and air flow. It has to be able to do that. The fan would aid in diagnosis, if you had the correct charge, but were seeing high pressures.
A good understanding of "theory of operation", and how components interact, carries a long ways in the diagnose of anything.
Tugly,
Yep she was low. Put in an 18oz. Pressures came up and held.
85* outside
49* at center vent @ idle
42* at center vent @ anything above 1000.
Low side 36 @ idle
High side 175 @ idle
Above 1000 NO compressor cycling
Low pressure drops to 28
Keith
Trending Topics
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Ah... that'll keep the Florida heat at bay, but I wonder about the Arizona heat. 42 degrees is a great result nonetheless.
I think I'm due for some refrigerant as well, I drove way too long with the air conditioning on the other day. In years past, icicles would have formed in the cab if I ran it that long.
I think I'm due for some refrigerant as well, I drove way too long with the air conditioning on the other day. In years past, icicles would have formed in the cab if I ran it that long.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
Thread
Thread Starter
Forum
Replies
Last Post