Yesterday i noticed that the ac did not work in either of its settings. All of the other locations on the selector **** blow air the way they should. The question i have concerning this is that i just had my heater core replaced, i was wondering if that could have had anything to do with the problem. Possibly in the removel of the system under the passenger dash?

the ac blew cold all summer and was last used about a week before the heater core was replaced.

any thoughts are appreciated.

 

does your compressor clutch engage when you put the interior selector switch into either A/C, Max A/C, or Defrost? If so, then you have either an "air blend problem" (most likely because of a vacuum problem) or your system has an inadequate charge of R-134a.

If it doesn't engage, then we will go from there.

 

from what i can tell, the compressor clutch does not engage. im not sure what ?sound? i would be trying to hear? but there is no change under the hood when its not on ac, and is on ac. thanks for the help

 

on the compressor under the hood (pulley), there is a plate that I think has three rounded bolt heads on it (someone else will tell you if it looks different, but they will all serve the same purpose). The entire piece, pulley and everything back that has hoses running out of it is called your compressor. It should be sitting over top of your power steering pump. The plate is called the compressor clutch-
With your engine on and the selector switch NOT in A/C or Defrost, the compressor clutch is not engaged...this means that it should not be spinning. When you move the selector switch on your A/C panel, this plate is pulled back into the pulley by magnetism (electricity is running through the clutch now), and it will start spinning. If it is not spinning, then you most likely (and hopefully) are low on refrigerant. Your truck should be running on R-134a. If you do not have a set of gauges to test for low pressure and high pressure, take it to most any service shop and have them inspect it for you. You can add the freon (r-134a) yourself very easily for a fraction of what they charge. But you will need to know the pressures before you start, and waste money on a can of refrigerant that you do not need. If the pressures are correct, then I will tell you how to check the electrical side when I see your post again.

Tim

 

also, sorry it took me a day to get back to you...had a rough day yesterday.

 

ok, i went out and check the plate, it is not engaging. it will take me some time to check the level of the refrigerant because all of that equipment is at home with my pops. when i do get a chance to check it, what should the charge be?

 

the pressures have a great deal to do with the outside temp (ambient temp). that question is better answered in the AC/Heater forum. I do not know exactly, but I think it should be around 45 psi on the LOW PRESSURE side. It is incredibly important to understand there are two sides to your a/c, a low pressure side (near your condensor/dryer on the passenger's side of the engine bay) and a high pressure side near your compressor (on the driver's side of the engine bay). A very simple test that you can check is to see if you have continuity across your Low Pressure switch. Do a search on this forum with "Low Pressure Switch" as the criteria and you will find a wealth of information. As a quick reference to you, if you look on the condensor/dryer, you will find an odd looking extension that comes off of the dryer (also where you would add freon) and it should have to wires running into it (one purple and one black with a colored chaser) find the plug that those wires run to, and check continuity across them. this can be done with the engine off. check this and post your findings on this board.

 

ok we did the electrical check over spring break(last week), and found that the compressor clutch will engage if its given power and that the pressure in the system checks out to be ok. tracing through the electrical diagrams, i can trace the "A/C compressor clutch" and the "clutch cycling pressure switch" to the "A/C clutch resistor diode". What and where is this "A/C clutch resistor diode". everything checkable checks out, and this is pretty much a last guess.

thanks for all your help on the front end of this problem and sorry for taking so long to get back to you all.

 

if you were to chase the two yellow or brown wires that lead from the clutch plate electrical connection back about a foot and a half through the wire, you will find the diode. I know, in my own personal experience, that I lost continuity from the Low Pressure Switch to the diode. I spliced from the LPS to the diode (bypassed the mess of wires on the driver's side fenderwell at the 100 pin connector). That was my unique experience, yours may be different. A good voltmeter with a continuity function and a known good piece of wire that you can "test" with is your best bet. Try jumping from the LPS to a terminal on the clutch plate and run a ground wire from the other terminal. Should come to life. Post your results, as other people should start to worry about their A/Cs soon.

 

ok, i lied, sorry. i must have missread and miss-interpreted the information. the high end pressure was ok, but the low end pressure was not. i asked a ford technician and he told me to check the pressure at the condenser, by pulling the connector, and jumping the pins. he said that if they system was low in pressure, when jumped, the clutch would engage. the clutch did engage, and i guess they system is low, i will go and refill the system tomorrow.

thank you for all your help timmy. i appreciate your time and effort.

 

i went out and got some refrigerant and put it in the system. the system says thats its charged to about 43 psi, but the compressor still isn't kicking in. if i have the have the low end sensor jumped with a paper clip, the compressor plate begins to spin, but the ac never gets cold. ill check tomorrow to see if its holding refrigerant, if it is, then ill have to try and find the diode.

the gauge on the can of R-___ said to fill the system til the pressure was between 25-45 psi. IS that correct for the Bronco? or should it be more?

Timmy, im going to go out and look for the diode now i may need some help finding it. ie. what does it look like, and is it buried in some sort of bundle.

thank you

 

went out and checked the system. for 2 hours or so, the system is holding the gas at 45 psi. now, with the ac system ON, the compressor plate will engage for about 2 secs, the needle will drop to 24psi and the plate will disengage, the system then charges back to 45 psi and the cycle will continue?

at this point i am lost. thanks for any help. (??is the diode in the 100 pin connector??)

 

You have it only charged to 24 psi. It needs to by charged to 45 psi while the compressor is working. When the compressor is running it is feeding coolant from the low pressure side to the high pressure side. If you charge it when the compressor is not running, then you are only getting coolant to the low pressure side.

End result, buy another can of coolant, turn on the a/c, and start adding. It will take forever, and you will see that the compressor will start running for longer periods of time when you are putting in coolant. It should take you about 15 minutes to put in a full can.