Ok, it was hot as crap today, and I had to make a couple of runs to the dump, so I thought I might investigate why I have no A/C. When I got the truck (last week), I noticed the compressor clutch was unplugged. I had assumed the compressor was seized, but that's apparently not the case. The PO did (I assume since it was a farm truck, the PO did it, and not a shop) an r134 conversion. The correct ports are there, as well as the sticker indicating it has been converted. I had a couple of cans of 134 and a pressure gauge left over from a few cars ago. I started the engine, put the indicator on max cool and checked the pressure. It's cycling between 25psi and 45psi. It will start at 25, rise to 45 over a couple of seconds and then drop back to 25 and start all over. At the same time, the compressor clutch is kicking in, running for a few seconds, then cutting off.

I understand how A/C works, but have no real experience working on a system. I'm assuming since the clutch compressor was unplugged, something is FUBAR, but I don't know enough to figure it out

Oh, factory installed A/C.

 

The clutch cycling is likely from the system being a bit low on refrigerant. It doesn't take much, too really start the cycling.

 

Yes, the compressor kicks off, the pressure in the system from the high side equalizes with the low side, and the pressure on the low side rises, kicks the compressor on, it pumps the high pressure side up, the low pressure side gets sucked too low and the whole thing starts over again. Put some freon in it.

 

Ding, ding, ding. We have a winner. Emptied a can of 134 in, pressure is steady at 45, and the A/C is working. Thank you both!

Wish I had figured this out this morning, LOL

Now I need to figure out why I can only get the defrost vent to work. I assume the doors are vacuum activated?

 

With no vacuum going to the system, it will default to the defrost vents. So the first thing I would check is the vacuum line running to and through the pass side firewall that supplies the system vacuum.

 

These 3 lines come in through the firewall behind the carb. The one on the left runs down to the death star looking black ball on the passenger side wheel well. The one in the middle runs down behind the carb to who knows where. The one on the right is capped. I recently plugged an open tee on the brake booster line. May or not be related. Is it possible the one on the right is for the HVAC?

 

IIRC the death star is for your HVAC controls.

 

That is actually just a vacuum junction, that doesn't go thru the dash.
The heat/air vacuum line should go thru the dash near the large box towards the passenger side of the firewall.

 

OK, I'm not seeing much. Here is the firewall, pass and drivers side.

 

Just above the blower, near the heater hoses. Is that the vacuum line connector? Looks like it has those hard plastic "spagetti" lines, and one crosses over the top of the heater hoses, while another goes to the vacuum motor (silver can on top).

 

Everything works in my truck. Maybe this picture will help. Is your vacuum solenoid working on the a/c box under your hood?

<a href="http://www.flickr.com/photos/love_ford_trucks/3668825307/" title="polished 059 by ford collection, on Flickr"><img src="http://farm4.static.flickr.com/3628/3668825307_75ee62bd5b_b.jpg" width="1024" height="683" alt="polished 059" /></a>

 

2 lines appear there. One goes to the silver canister, with some kind of armature on the back. No idea what that is. The other (the one that crosses the heater hoses) runs down to a tee. One end goes to the death star, the other to the vac junction I took a picture of before.

 

That armature is pretty crusty. That is supposed to open the interior cab air and close off the exterior air.

 

Yep, it's definitely crusty. I haven't checked to see if it's operational yet, but I'd rather sort out having air come out of the right place before I deal with the inside/outside air issue. I don't suppose there's a vac diagram for the HVAC system somewhere?

 

The one with the tee that goes to the vacuum ball should be the one. The line should run over to the tee, with a plastic thing in the line before it hits the tee. The plastic thing is a check valve. After the check valve it runs to the tee, and then runs to the ball which is a reservoir(vacuum storage tank) and the other side of the tee should run through the firewall and under the dash to the controls.

With the engine running, pull the line off going into the firewall and see if the tee sucks on your finger.