I am new to the forum here, so hello to everyone. I have a 92 6 cyl. automatic, and the 134a is low in my system (I had the a/c system replaced a few years back, and yes it is out of warranty now). I wanted to service it up and try to check for leaks somehow, but the compressor clutch isnt engaging. I looked in the power distribution box, and there are 5 slots over to the right hand side for relays, but only R1, R2, and R3 are populated. I dont have the original manual for the truck as I bought this truck VERY used almost 5 years ago. Is one of these relays the ac clutch relay, and if so, exactly what pins in the socket do I jump? I read one thread that described some kind of switch on the dryer, and I believe they called it the clutch cycle switch. Not to sound stupid or ignorant, but I dont know what the dryer looks like, where it is located in the engine compartment, or what this switch looks like, or what terminals on the switch that I need to jump. Is this clutch cycle switch the relay I am looking for? I looked on the internet and didnt find anything, yet. Any help would be appreciated, as I live in Florida, and it is starting to heat up down here. Thank you, and may God bless you.

 

The thing you are looking for is on the pass side, its cylindrical, there should be two or three wires sticking out of the switch, but most likely there is not enough freon in the system to build up the pressure to turn the switch on, which activates the compressor, and jumping the switch will likely cause damage to the compressor, you can go to your local parts store and get a recharge kit for around $20.00.

 

If you know the system is low on freon, the likely culprit is the low-pressure switch on the dryer. This is over on the passenger side of the firewall near the fan enclosure. It looks about like a vertical 32oz black can of your favorite brew.

There should be a freon port on the line into this canister. Nearby - either on the line or on the drier - should be a switch - has two wires going to it. To check - just pull the connector and short the connector out with a jumper wire. Only two wires - hard to go wrong. If the compressor pulls in - you've found the problem - low pressure.

The purpose of the switch is to disengage the compressor when the pressure drops below about 22-28psi - first to prevent the evaporator from freezing up, and second to protect the compressor.

If you choose to attempt a recharge yourself - first, be careful. The extreme pressures and temperatures involved with A/C will put a hurt on you in a hurry if things go wrong. Hand and eye protection are 'musts' in my book. Next - there is the issue of possible equipment damage which could cost you more than having the system professionally recharged.

Recommend to use gauges on both the high and the low pressure ports. The low pressure is next to the drier, the high (at least on my vintage) is on the driver side as the freon line approaches the condenser by the radiator.

The ambient temperature plays a large part in the pressures seen - but I try to charge things until the high side is around 300 with the low side around 30-35, with the engine turning about 2000 rpm. I won't charge above 300 psi, but try to get the low side above 30. The R134 conversion will not put out the amount of 'cold' as the stock R12 system, but things are kept quite comfortable by kicking the fan up a notch. Heat isn't so much a problem here in S.E. MO as humidity - many summer days the evaporator will be streaming water out the drain, so a big portion of the cooling is expended condensing water.

For the R12 to R134 conversion - it was recommended in the playbook I used that the low pressure cutout be adjust from its stock setting of about 28psi to about 22 psi. Rule of thumb is 3/4 lb R134 for each 1 lb of recommended R12 charge. The best way to charge is to put the recommended amount of freon in, but --- that's never stopped me from charging to desired pressures. :-)

Welcome to the site, good luck, be safe, and keep us posted.

 

Thank you both (wde3477 and dirtcrew51m) for your responses to my post. I found the dryer with no problem, and saw the connector that was plugged into the a/c low pressure switch, or what some call the a/c clutch cycling switch. I pulled out the connector and jumped one terminal to the other terminal, and then started the truck, and then turned on the air conditioner. The a/c clutch engaged, so I am definitely low on freon. Before all the aforementioned steps, I spun the a/c clutch by hand to make sure the compressor wasnt locked up, and it spun fine. I wish I had more time to mess with it, but I have to leave for Alabama tomorrow right after work to spend Easter with my fiancee. I will try to finish this sometime early next week. Incidently, I will be driving my 2003 Ford Taurus there. It does great on long trips, and no Taurus has ever left me stranded on the side of the road. I am a member of the Taurus Car Club of America forum as well. For the most part, I have always been a Ford man. I have owned a 68 fast back Torino, a 70 Torino, a 70 Falcon, an 84 Ford F150 4x4, a few Escorts, a Contour, a 2000 Taurus, and my current truck is a 92 F150.

 

I got back from my trip to Alabama, and eventually went out to the truck to work on it. I jumped the low pressure switch, and (with the engine on and dashboard controls set to max a/c) the compressor came on. I put one regular size can of 134a in with the store-bought line and gauge assembly (very cheap). At this point the pressure read 25. I then started putting in the second can of 134a, as the truck was low on freon. When it was near empty, the pressure read 20. Not good. Very bad. I knew for a fact that I have a leak somewhere. I finished charging from that can, as it was mostly depleted anyway, and climbed in the cab to shut off the truck, and did so. In the quiet, I could hear.....hissssssssssss. It was coming from somewhere inside the dash about midway. I know that the evaporator is in there, and some kind of valve as well. Apparently that is where the leak is. I know that pulling the dash down to get to all this will be a monstrous job, and there is no way I can afford to pay someone to do it at this time, so I guess I am going to do it myself. Any advice from you knowledgeable people out there would be appreciated, as well as cautionary notes to avoid pitfalls and mistakes, as I have never done anything like that on this truck. I did something like this on an 84 honda accord many many moons ago when I had to replace the blower motor, and it was a challenge and then some. I am not sure of what I will find in there, but I would like to know for sure which part is the culprit before I put it all back together again. Again, any help would be appreciated. Thank you and God bless you and your families.

 

to replace the evaporator u have to do all the work on engine comp. its no that hard specialy if u have a 6L i replace mine while ago its a V8 more things on the way. any way . empty the system before u remove the hoses. remove the hoses that connect to reciver dryer and move it out of ur way. right bihind the big black box its the evaporator. just look for all the screws holding the cover and remove it. you see the evapoator there. whe u get the new and ready to put every thing back togethere. make sure u seal the cover with some type of silicone to keep cold air to leack out and keep warm air from engne to get in. one more thing its good idea now that u have the system apart to replace as many O-rings as u can from the conection, and make sure u replase Orfice tube too. new Orfice tube make lot of diferece in system.