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AC clutch

1995 f150 5.8 259k

My AC clutch won’t engage, with a gauge connected it is reading about 35-40psi. I read online that clutch could not be engaging bc minimum is 45 psi. Since the clutch isn’t engaging, I’m hesitant to pump it up that high. The green filled zone only goes to 50psi. Should I just pump it up to 45-50psi and see if clutch engages?
 

SuperCab

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Staff member
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Montana
You're probably low on refrigerant. The low side numbers in the green section of your gauge are under suction, with the compressor running. Static pressure Id expect to see probably 50-60 psi. Add some and see if your clutch won't engage.
 
So With the pressure in the green, the air is still not cold. Also when I go fast or really slow, the vents stop blowing and divert to defrost, why?
 

dustybumpers

don't play well w others
Vacuum leak Look under the hood by the heater box. There is a black and a white vacuum line goes in the cab with the wiring harness. The heat disintegrates these. Get some rubber line that will fit those lines, and patch them, problem solved

Going into defrost is default

If your still not cold enough on your a/c you probably are about 6 oz short. ( 1/2 can)

I have pictures somewhere of that vacuum line, but since my other lap top crashed, I haven't been able to retrieve them
I guess I need smokey.LOL
 

dustybumpers

don't play well w others
They could also be bad right where they come down inside the kick panel, and cross over the bottom of the heater box. sometimes people catch feet in them

Other problem, Not sure about your truck, some had a metal "juice can" as a vacuum reserve on the passenger inside fender.
That rusts out on the bottom where the bracket sits, and no longer holds vacuum in reserve
Some later trucks, this "can" is plastic, and won't apply to you

If it's going from center to defrost when you step on the throttle, it's in those 3 spots.
 
Thanks!! I have he plastic juice can but I found a spot in the line that I thought was fine but had a mark, I clipped and replaced and it works at all speeds now!

I will add some more Freon and see if it cools it down.

Thanks!
 
I’m sensing a pattern...I fill it up full charge and then it only blows out of defrost. It was fine (blowing from vents) before I charged it...
 

dustybumpers

don't play well w others
It's in the vacuum. keep looking. It may be in the lines that come around the box inside. someone may have got their feet in them

Last thing, could be the control in the dash. they don't usually go bad, but your truck seems to be outside the usual curve sometimes.

Like I said, it is vacuum.
 
If I had a dollar for every time you were right...found a complete broken line where that T connector is, AC fully operational! On to the next problem.

Thanks!!
 

dustybumpers

don't play well w others
No prob! Glad to help
 
So I’m thinking I have a Freon leak. This seems to be a yearly issue. Again, clutch wouldn’t engage, so I hooked up the full pressure gauges to see pressures and it started engaging intermittently (weird but ok). Both pressures read 50psi, so following a little troubleshooting guide, I visually checked wiring to compressor and then started adding Freon. I could only get the pressures to 85 psi, nothing higher. So my thought is that I have a leak so bad that I can’t even get the system pressurized. However, it does hold pressure at 85 psi (I checked it the next day). So now I’m wondering where to start? J heard there is dye Freon so I can try to see where the leak is? I have no problem replacing parts, I just don’t know where to start.

Thanks guys!
 

dustybumpers

don't play well w others
Look for oil on any connection, and there is the leak.
Start at the compressor, dont forget the ports where you add and test. Many times the leak is there.

Sent from my SM-N960U using Tapatalk
 
the dye youll need a UV light to see... even from factory they are prefilled with a high viz green... Mine has a mix of the High Viz Green and high viz red (when i repair my systems i dont have the green dye.. i have red)..

common places ive found leaks tend to be around the compressor pulley and like charlie said the actual fill fittings themselves... the shrader valves have a bad habit of going bad, especially on older systems that have been converted from r-12 to 134a.. being a 95 yours isnt converted.. the high pressure relief valve is another common point for failure as well.. and that silver in line cylinder thats on the rubber lines near the compressor... i frequently find pinholes around the base of the cylinder where its welded together..


something else to keep in mind when it comes to the pressures... your ac system pressures will change depending on heat and humidity outside... the higher the temp outside the higher your pressures will be inside the system... the colder the lower... part of why you need to know what the pressure values are for your particular vehicle at the various temps..
 
So I took another look and found the high side port pretty oily. It also hisses when I take the cap off, is this normal?

Do you guys know good resources to find specifics on my truck? Chilton doesn’t have anything on ac and Haynes only has replacing parts.

Thanks!
 

dustybumpers

don't play well w others
Not normal. You found a leak. Maybe the only one, maybe not. There is an oring in there. Sparkey probly has a chart. If not I think I saw one on another site. Once the repairs are made you need to vacuum down the system and have it hold for at least 2 hrs.
Then charge it.

Sent from my SM-N960U using Tapatalk
 
Not normal. You found a leak. Maybe the only one, maybe not. There is an oring in there. Sparkey probly has a chart. If not I think I saw one on another site. Once the repairs are made you need to vacuum down the system and have it hold for at least 2 hrs.
Then charge it.

Sent from my SM-N960U using Tapatalk



only charts i have are for the mustang... dunno if theyd be the same for their truck... what ive always wondered tbh...
 

dustybumpers

don't play well w others
I found them for the trucks, just have to copy paste tomorrow

Sent from my SM-N960U using Tapatalk
 
Awesome thanks!!

Also if I am going to evac the system to replace oring and possibly the whole manifold hose assembly (?), is there any other parts I should replace while I’m at it? I don’t have much faith in these newer parts so I would rather not unless you guys recommend it.
 
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