2006 Dodge Ram - AC Short Cycling Poor Cooling

[C172]

06 dodge ram ac not cooling, thought may be low on freon, evac and recharged, no diff, compressor stays engageded 15 to 20 sec when first turned on for 2 minutes then only stays engaged for about 4 sec at a time loosing cooling capability. changed out preasure switch, no change. data stream appears normal compared to other truck.

anyone come across this before??? thanks jack

[jbadenoch]

what are the pressures when comp is on. what are temps at condensor and evap core when comp running.

[Tim Martin]

That same cycling will occur if freon level/pressure is too high. Yea, I am asking the same question: What are the o/off pressures high and low side?

[Jeff @ Able Auto]

Had a Caravan in last week doin the same thing. Had no pid for evap temp sensor, everything else was in spec. Repalced evap sensor and all was good.

[steven kiser]

take a look at the expansion vale.with the gauges if the high pressure spikes and low tanks try tapping the valve. i've seen a bunch freeze up over a winter. it also may be a filter issue if this one has one in it. another possibility is the evap canister. i'm leaning towards an expansion valve.

[C172]

finally got the truck back in shop. gauge preasures low side compressor 65 high side 75 ac off. ac on compressor kicks in at 65 low side and kicks off at 40. high side on 70 and kick out at 100. after running 15 min low side 65 in and off at 45-47, high side in at 80 and out at 125. engagement only last about 4 sec. scanner refrig preasure on 5.0 bar and off at 8.5 bar. scanner refrig temp running between 30 degree and 37 degree. 65 degree shop. with engine off scanner refrig temp 47. no sign of expansion valve in this system. tryed to add freon but hard to take because compressor only on for short time 4 sec. cant see what might be keeping the compressor from running longer?????? thanks jack

[JBUTITTA]

I have had many chrysler coils that were to weak to hold the shoe engaged when hot. Have you checked to make sure you are loosing power to the coil? Jerry

[Jeff @ Able Auto]

I believe the temp sensor is your problem. With such a short cycle I dont believe it could get that cold. Just MHO.

[C172]

WATCHING THE SCANNER I BELIEVE THE COMPRESSOR IS KICKING IN WHEN TOLD TO AND OUT WHEN TOLD TO. THE TEMP SENSOR, IS THE ONE IN THE EVAPORATOR BOX, IE TAKE THE DASH OUT???? THANKS JACK

[Jeff @ Able Auto]

Yes according to repair data. Before pulling the a/c box I would monitor the temp sensor with key on engine off. The start and turn on a/c and monitor sensor temp. At the same time ya could measure the air temp out of the vents and maybe check the low side line temp coming out of the evap and compare to evap temp sensor. HTH.

[C172]

recieved temp sensor today will try tomorrow. thanks jack

[steven kiser]

the expansion valve/orfice tube is located in the liquid line between the condenser and evaporator. the quick test is while it's running see if there is an extreme temp difference between hoses or if one side of the valve is icing up. it seems that the recommended repair is to replace the line. any time i find a valve that the screen is plugged i flush the system. i also explain to the customer that anything from the compressor through the condenser may be contaminated or failing and need to be watched.

[C172]

before pulling the dash and the box out of the boss' es truck . hooked up temp sensor outside of box, and now compressor stays running. but not cooling like it should about 48 degrees at vents. thanks jack

[steven kiser]

let's get back to basics here. the principal behind air conditioning is that the air isn't made cool but the heat is removed from it. an example would be, if the temperature outside the vehicle is 80 degrees and the temperature at the vent head is 60 degrees it's normal. this figure is just being thrown out. i'm not sure of the exact number without looking it up. you also have to figure in humidity. on a 90 degree day with high humidity it will take forever to cool down the cab. for some reason g.m's seem to cool faster. as a matter of fact when a customer comes in on days like this i try to hold the vehicle over until the weather changes. . if the pressures are correct and you're seeing a 20 degree drop in the cabin i'd say you're pretty good. the sensor being out of the box and the system continually running is normal. watch the head pressure and if it slowly climbs with increased rpm until the pressure switch kills it you're issue may still exist. the other issue may be that the evaporator may be icing up. if there is any contamination in the fins it has to be removed or the evap must be replaced. a/c can be a pain in the butt. if you don't understand the principal you may find yourself banging your head against the wall. i have a 5'10" blonde at home that is the "A" typical customer when it comes to hvac. during the winter she'll walk over to the thermostat, turn it up, wait about 20 seconds and come and tell me that house is still cold. i've tried to explain to her that it's a thermostat not a transporter. you don't press a button and suddenly find yourself in the Caribbean. just as well as when i come home in july, 100 degrees, so humid you can cut it with a knife, i walk in the house and i get chilled, she claims the a/c isn't working because she's still warm. all the shades are up, we have 13 windows with sun beaming through. i've quit trying to explain the principal of a/c to my wife. i pull the filters and clean them, take her outside and walk her around the house showing her the water pouring out of the drains and such. i keep her outside long enough to get her sweating and when we go back into the house suddenly cleaning the filters made all the difference in the world. i make sure all or as many as possible of the vehicles i've charged the a/c on are parked in the shade when the customer picks it up. try to explain to a customer that owns a black caddy with a black dash that's been in direct sunlight all day who just spent 15 hundred bucks that it's going to take a bit of time for the a/c to remove the heat, cool off the vents and start to drop the temperature. we're coming into what i feel is going to be a strong a/c season. most of my regular customers are all set because we have already checked the a/c during routine service. i'm just glad my shop isn't in Mississippi or Louisiana. the humidity is going to be a killer. mount a generator in the trunk and hang a 10 thousand btu a/c unit in the passenger window of your customers vehicles. don't know where all this is coming from. maybe because i was fishing all day yesterday, got soaked and dried off many, many times. argued with people that tried to cast into the hole i fish in and crossed my line more than once forcing me to real in and recast, tried to look into my bag to see what i was using for bait, argued with me about how many trout i caught since i caught 12 or 13. apparently they were confused about catching and keeping, insisted that i should move so they could catch some fish also, got upset because i wouldn't give them my throw backs and when i came home stretched out in my recliner and dozed off while watching the race only to be awoken by my two do tugging at my shirt and pants. they weren't there when i got home because if the were i have to strip down because they love the scent and taste of the bait and fish blood and slime i get on my cloths. they were trying to pull my pants down and i yelled for my wife. when she came into the room i told her she should take lessons from the dogs. that's when the fight started. she decided she needed new sheers in the living room and insisted i come with her. when i got home the hoard had come through and all the meatballs were gone from the pot. i have to stop now because i'm on the verge of a record breaking post...............

[jbadenoch]

You go steve. Have a good weekend huh

[Gerald Martin]

Steve that wasn't a rant was it?

[steven kiser]

maybe sometimes one thing just leads to another. since i'm on the subject, what about arnold and maria breaking up? i thought it was a democratic verses republican issue at first then i found out it was that he knocked up a member of the house hold staff. hey, wait a minute here, mmmmmmmm, he's a republican right. as far as maria felt he was always screwing up and i'm wondering if the maid was on top. maybe tim will let this fly but then again i think he has a built in alarm that goes off when i post. this circles political and other no no rules but just barely so it may fly................................

[protraxrptr17]

Is this a diesel? I had this same problem on a diesel before and it was the fan clutch. It is electrically actuated. The air would work fine for just a minute the the high side would peg and the compressor would start cycling rapidly. You can monitor fan rpm and desired rpm on your scan tool to check it.