What cycles the AC compressor?

[JONAS78028]

I'm getting ready to convert my AC system over to 134a.  I have a new drier and expansion valve on my workbench and plan to flush the system and drain the compressor of old oil.
My question is... What cycles the compressor on and off?  Shouldn't there be a pressure switch somewhere?  I'm going to go back and look again but I didn't see one.

[amcfool1]

hi, afaik, with the switch in either AC, or, Max AC position, just turning the fan on activates the system, ie, turns on your ac. good luck, gz

[eaglefreek]

There should be a low pressure and/or high pressure switch, but I no longer have an Eagle to look. Here's another thread. http://forums.amceaglesden.com/index.php?topic=43466.0

[AMC of Houston]

I forgot what year your car was -- but if its an '82 or later, with factory AC, and a 6-cylinder; the switch should be in the line close up by the dryer (left front of the engine bay).

[vangremlin]

What year is your Eagle?  I'm not an expert on AC, but it is my understanding that for the earlier Eagles (pre 84 or 85) with the York compressors, there was no pressure switch.  The pressure switch on the later Eagles was to the left (driver's side) of the radiator where the hoses come through for the condenser, and it fed into the power feed to the compressor.

I converted to the Sanden (rotary) compressor from an 85 Eagle when the York compressor on my 80 Eagle coupe went bad.  I wanted to put that pressure switch into one of the AC hoses on my Eagle, but couldn't find a shop to make a short adaptor hose that would connect with the existing hoses.  It would have required making a full new hose and I didn't want to go through the bother of pulling the AC box in the car to attach the new hose, so I went without the switch.

As far as activating the compressor, its like amcfool1 says, turning on the fan while its in AC or Max AC position will turn on the compressor.  I think the AC "thermostat" (not the right term, but its the little probe that sticks into the evaporator) will then turn the compressor off once the desired temp is reached.

Good luck!

[mo.eagles]

There is a low pressure switch at the sight glass . It is located on the drivers side of the radiator .

[JONAS78028]

I found it... as per previous post above... it's on the drivers side of the radiator right where I overlooked it...   
 Thanks everybody!

[JONAS78028]

The AC system on this Eagle actually has a charge... just not enough to cool things down.  It's been so long since I have messed with an R12 system that I totally didn't consider simply adding R12 to this vehicle.    Everything that I've worked on lately either has 134a or has already been converted.  Now I just need to find adapter fittings for my gauge set...

[trucker79005]

The AC system on this Eagle actually has a charge... just not enough to cool things down.  It's been so long since I have messed with an R12 system that I totally didn't consider simply adding R12 to this vehicle.    Everything that I've worked on lately either has 134a or has already been converted.  Now I just need to find adapter fittings for my gauge set...

Where were you able to find the r12? I've been looking on ebay and don't want to get ripped off but I have my Eagle and a 71 ford pickup that haven't been converted yet.

[eaglefreek]

The AC system on this Eagle actually has a charge... just not enough to cool things down.  It's been so long since I have messed with an R12 system that I totally didn't consider simply adding R12 to this vehicle.    Everything that I've worked on lately either has 134a or has already been converted.  Now I just need to find adapter fittings for my gauge set...

If you can keep it R12 that is the best thing to do. With r134, my Eagle cooled mediocre at best.

The AC system on this Eagle actually has a charge... just not enough to cool things down.  It's been so long since I have messed with an R12 system that I totally didn't consider simply adding R12 to this vehicle.    Everything that I've worked on lately either has 134a or has already been converted.  Now I just need to find adapter fittings for my gauge set...

Where were you able to find the r12? I've been looking on ebay and don't want to get ripped off but I have my Eagle and a 71 ford pickup that haven't been converted yet.

Try Craigslist. There was 4 cases somewhat local to me about a month ago. The guy wanted $150 for a case of 12. I was going to buy all four, but they sold before I got back into town. They typically sell for about $25 a can near me, but I've seen them cheaper and some have wanted $40-50 a can.

[AMC of Houston]

I use one of those "heavy-on-the-butane" "drop-in" R12 replacements (currently use the Freeze-12 brand, 'cus I got a bargain on a few cases a while back).    Then there are those who tell me my car will explode using this stuff; but I'm not worried since I'm sitting on 15 gallons or so of high explosive every time I go for a drive!!    Your mileage (or fireball) may vary........

[trucker79005]

Try Craigslist. There was 4 cases somewhat local to me about a month ago. The guy wanted $150 for a case of 12. I was going to buy all four, but they sold before I got back into town. They typically sell for about $25 a can near me, but I've seen them cheaper and some have wanted $40-50 a can.

Not really sure why I hadn't tried craigslist yet. I look on there for everything else..

I use one of those "heavy-on-the-butane" "drop-in" R12 replacements (currently use the Freeze-12 brand, 'cus I got a bargain on a few cases a while back).    Then there are those who tell me my car will explode using this stuff; but I'm not worried since I'm sitting on 15 gallons or so of high explosive every time I go for a drive!!    Your mileage (or fireball) may vary........

I'll have to look into it. Is the "drop in" compatible enough that I could have someone use this first and then once i know the system isn't leaking use the real stuff?? I haven't figured out any other real good way to tell if my system is good other than charging with nitrogen and I'm not having a lot of luck getting that done.

[AMC of Houston]

Supposedly the drop-ins are compatible and mixable per their sales drivel.   I know I've done in on my '85 Eagle with no issues.

[eaglefreek]

One issue with mixing them is if you ever need to get it serviced, you may have a hard time finding someone who will evacuate the system for you.

[AMC of Houston]

Unless you don't tell them what's in it!!          I have a vacuum pump.............