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This is on 1980 Custom F150 with factory air.
The AC is not coming on.
The clutch on compressor is not activating. I jumpered 12v to it and it activates. The problem is the switch (in the EVTM book is says that switch is Clutch cycling Pressure switch.
Picture:
Is this lack of refrigerant causing this switch not to close?
Most likely yes but you should put a set of gauges to make sure. If it is low on charge why is it low?
When has the system last been serviced?
Is it still running R12 or been converted to 134a?
You can't get R12 and you can't just put 134a in the system without doing some service work first.
Dave ----
It was converted to 134 when compressor was changed about 10 years ago. I don't want to get into that side of it, I guess I will take to shop and see if they can put die in it to see if there is a leak?
Look the A/C system over. Any oily areas is a leak. If the front of the compressor behind the pulley is oily and dirty, the seal on the compressor is leaking. Any fittings that are oily are leaking. If you want to verify it's the low pressure switch, unplug the plug and use a jumper to jump across the plug. If the clutch kicks in then you know that is the problem. That will verify all your dash controls are working.
Look the A/C system over. Any oily areas is a leak. If the front of the compressor behind the pulley is oily and dirty, the seal on the compressor is leaking. Any fittings that are oily are leaking. If you want to verify it's the low pressure switch, unplug the plug and use a jumper to jump across the plug. If the clutch kicks in then you know that is the problem. That will verify all your dash controls are working.
If it has been changed over to 134a you can get 134a with dye in it so you don't have to open the system to pour it in.
If you open the system you have to pull a vacuum so you need a pump and gauge set.
So you can get a can with dye and add it to the system to get it in. Then you need a black light to see the dye.
Yea it may be best to have a shop look it over.
Then if it fails in a short time take it back and have them fix it free.
Dave ----
It was converted to 134 when compressor was changed about 10 years ago. I don't want to get into that side of it, I guess I will take to shop and see if they can put die in it to see if there is a leak?
If it was converted to R134a 10 years ago and it was never serviced in those 10 years then you are low and thats why its not coming on. The AC compressor shaft seal is not a 100% seal it is why those trained in the HVAC area even mobile HVAC, to urge people to get their systems serviced yearly as all systems no matter what you do will leak. In a 10 year span you would have leaked enough out your pressures would have became low enough for the switch to not trigger the clutch.
It doesnt hurt to have dye added to the system either. I am contemplating disconnecting my system if its low when I get my engine in and flushing the whole AC system out with flush then add straight pag oil with dye for a full charge and then recharge the system.
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