A/c Help please

RocknC · 06-30-2009, 01:36 PM

Hello guys, I have been trying to figure out my a/c for a while now and no luck so I figured I would see what you guys think. Last summer and this summer as well the a/c works great as you are driving down the road (highway) but you get into town or stop at a light, or idle and it dont blow cold hardly at all. I put guages on it and pressures look good and had a shop make sure i had enough freon in it but you can hear the a/c compresser kicking in and out every few secconds to a minute, the pressure will go up and it will kick out then pressures drop and it kicks on etc.... Someone told me that it needed a new fan clutch but im not spending $456.00 to see if it fixes it. Hopefully someone can help as its about 102* here with a heat index of 115.

***Hayseed*** · 06-30-2009, 01:59 PM

Get a house type fan and put in front of your truck in the driveway. Put it right in front of the condenser and see if that helps the A/C. Don't use the "feels good" method, use a thermometer. If you see a significant difference then the fan clutch is bad. If not then the compressor may be getting weak. What are your pressures at idle? Does the high pressure go up after idling for 10 min or so? If you have a bad fan clutch then the high pressure should increase about 100 psi but putting the electric fan in front will bring it back down.

coblanchard · 06-30-2009, 02:06 PM

Sounds like either you are not getting enough airflow through the condensor or the system is low on refrigerant. Make sure you don't have any debris in the condensor, aftercooler, radiator ect. What are your pressures at idle when the compressor is running? Does the high side get really high, then the compressor cuts out, or does the low side get really low then the compressor cuts out?

RocknC · 06-30-2009, 02:11 PM

High side gets high then cuts out, I dont have a set of guages but when hooked friends up to it thats what it did, I cant remember the pressure readings. Refrig. is not low. Going to go check air flow now, clean some things out and see if it helps.

***Shibbyutman*** · 06-30-2009, 02:16 PM

if your fan clutch is bad or going bad it will not fully engage the fan to spin up and move the air through the coolers. The lack of airflow will obviously make the condenser not do it's job and allow the refrigerant to recirculate back to the cab warm rather than cooled as it should be. This is most likely whats causing your problem.

coblanchard · 06-30-2009, 02:26 PM

Without getting proper airflow through the condensor the high side will get too high and trip the high pressure switch. That would explain why it is cycling so much with the proper charge of refrigerant. It may very well be your fan clutch since it only happens when driving slowly.

RocknC · 06-30-2009, 03:01 PM

pulled condenser, intercoller, etc. to radiator and found what you cant see of the radiatior was pluged solid.....in process of cleaning it out its kinda hot out so time for a break....ill let u know if this solves problems. hopefully it will

RocknC · 06-30-2009, 03:34 PM

Alright, it helped out a LOT, i need to get a thermo guage to put in it to see what temp its actually blowing at but a huge difference by cleaning out the radiator! wow, the A/c pump does not kick on and off anymore. Still nothing like a ford a/c but at least I can ride comfterble.

***Hayseed*** · 06-30-2009, 05:10 PM

Good deal. Sometimes you need to answer the simple stuff first, good call cob.

coblanchard · 07-01-2009, 02:27 PM

Another problem with the a/c not cooling great is because they are running hot coolant through the heater core with the a/c on. A simple manual ball valve in one of the heater core hoses to shut off the coolant during the summer has worked very well for some people.