A/c problems

Topic: A/c problems (Read 1716 times) previous topic - next topic

A/c problems

July 17, 2013, 09:18:09 PM

What's up guys! I'm having problems with the A/C on my bird. The last couple of times I drove it, at 1st it would work great and blow cold. Then suddenly it would stop and blow hot. It's been low on freon in the past so I went and bought a can.

When I went to charge it up I noticed that the compressor never kicks on. I put a gauge on it and it reads extremely high (like 100 psi). I'm no expert in this area so any help would be appreciated. Could it be some sort of switch??

I will also say that for the last couple of years I've noticed that with the A/c on the motor surges somewhat and seems sluggish. I just figured this might be because the poor thing has almost 200k on it...

Anyway, any suggestions would be appreciated.

A/c problems

Reply #1 – July 17, 2013, 10:29:38 PM

The low and high pressures will equalize to about whatever the ambient air temp is when the car is cooled off. So if you check the pressure when the car is completely cool and engine off, if it has anywhere near the correct charge it should be close to the ambient air temp. If this is the case, when you turn on the a/c there should be power at both sides of the low pressure switch and the high pressure switch. Check the low pressure switch first, if both sides do not have power your switch is suspect. If there is power at both sides move on to the high pressure switch and do the same.

If the charge appears to be low or high, I would have the system serviced by someone with a a/c machine.

A/c problems

Reply #2 – July 17, 2013, 10:38:46 PM

http://www.pacificseabreeze.com/tech-library/heat-and-insulation/R134a-PT-Chart.htm

USE THIS CHART FOR PRESSURE TEMP RELATIONSHIP IF YOU HAVE 134a FREON IN YOUR SYSTEM. YOU DID NOT SAY WHAT FREON YOU ARE USING.

So if you are reading 100 PSIG it is app 86* Outside when you checked it.

With that your AC should come on and the clutch should engage if the wiring and switches along with the clutch coil are good

So first thing is to apply 12 volts to the compressor and see if it RUNS or engages. If it does the clutch is OK. Then go to the CCOT cycling switch on the side or top of the dryer accumulator. Apply battery to one side and the other. If the clutch engages that part is OK. If it only works on one side the switch is shot. if test is ok > Then make sure then ac is on and controls set properly and check for battery at the CCOT switch. Most likely there will be no battery if the previous tests panned out. Then it is off to the dash to find out why the clutch is not getting power. The WOT relay has to be checked as well as the controls on the dash. Good luck

A/c problems

Reply #3 – July 18, 2013, 07:42:48 AM

The best way to proceed with diag is to have the car running with the ac on. locate the clutch cycling switch and disconnect it. While disconnected, there should be power on one of the terminals but not on the other, connect a jumper wire between the 2 and watch for the clutch to engage. if it does, get a cycling switch (assuming the terminals are in good shape) if it doesn't engage, leave the jumper wire in and check for power at the high side switch, jumper that switch does the clutch spin up? If yes, replace
the high side switch (same assumption), if no, see a pro. With the heat we've been seeing, 100 psi when the system is static, is potentially normal, but not a great indicator of charge state.

A/c problems

Reply #4 – July 18, 2013, 10:02:40 AM

you may wanna reword,,,

The best way to proceed with diag is to have the car running with the ac on. locate the clutch cycling switch and disconnect it. While disconnected, there should be power on one of the terminals but not on the other, plug the clutch switch back in and then connect a jumper wire between the 2 terminals and watch for the clutch to engage.

A/c problems

Reply #5 – July 18, 2013, 10:20:53 AM

I was offering my diag routine as an alternative, wherein the clutch would not have been disconnected in the first place.

A/c problems

Reply #6 – July 18, 2013, 11:58:24 AM

I played with my car last night after reading this thread. I have low pressure (never looked into it before). if I jump the high pressure switch, my ac is nice and cool. gonna pick up a couple cans and see if I can find a leak this weekend and see how well it works. any way to test the switch on the accumulator without filling with coolant?

A/c problems

Reply #7 – July 18, 2013, 09:37:33 PM

just curious if any of you actually pulled the print for the clutch circuit wiring on a 1988 T bird 5.0. I am assuming this is the car he has. Pull a print and then post the diagnosis. I am curious what you find and why you posted the trouble shooting PARAMETERS the way you did.!!!

HINT !!!!!
FUSE 17
Heater AC controls no AUTO TEMP
CCOT
WOT RELAY
CLUTCH COIL

A/c problems

Reply #8 – July 19, 2013, 09:13:24 PM

Wow thanks for the detailed responses guys. I'm going to try and work on the bird tomorrow so I am sure I will be checking the thread again. I just took the wife on a nice little getaway to French Lick, IN and it sure was nice cruising around in my Mustang with the A/C set on MAX.

With this heat it's even hard for a new car a/c to keep up, let alone a nearly 30 year old system that's original other than switching to R134a!