A/C problems

[iviper123]

my ac isnt working my clutch engauges but it cycles on and off real quickly and when it engauges my rpms drop by about 300rpms, seems like a big rpm drop

 

[Acesneights1]

It needs a recharge.

 

[iviper123]

ive added more 134 to it but nothing seems to help still hot air.

what are the pressures supposed to be on the low side mine rises and falls quickly when the compressor stops the pressures spikes up to 45 then the commpessor turns back on untill about 25?

 

[packratt]

put a jumper in the plug at the drier can. This will keep the compressor running and you can get a good reading on the gauges.

 

[Acesneights1]

pressures vary depending on ambient temp which is why I always say you can't charge a GM by pressure. It's not what the pressures read as it is more important the diffreence between the two The swtich on the drier could be bad. Jump it like packy says and see if it cools. Could also be the dash controls not sending proper reading.
If you are reading 45 with it off you probably need more. Sure there isn't a leak and it's leaking back out ? If the truck sees dusty conditions Finding a leak can be as easy as sex with a fatty. Just look for the wet spot....Otherwise need a sniffer(not for the fatty..). Aviod Dye at all cost. it is a last resort.
If the system is completley empty usually holds around 2.5 to 3 lbs of refrigertant (excluding suburbans with rear air) but should be a label to tell you exactly how much.

 

[docdray]

adding a little to ace's post-normally you want a good, large fan sitting in front of truck feeding it air. how old is drier? about normal non-running pressure low side should be 80. compressor will kick off at 25, normal running low side about 35-45. high side about 250-300. a lot of issues determine pressure and adequate fill. temperature, humidity, condition of drier, etc.
sure the heater door is closed?
best way is to have a thermometer in vent, run 1500 rpm, watch high side-it can tell you if there are restrictions- feed low side while watching high side and temperature. when you get about 40 degrees or refrigerant floodback you've gone far enough. my 94 took 4 regular cans.

 

[Acesneights1]

4 cans is about right. Remember those cans are 12 oz not 16. rare to get 40 degrees on these older trucks. I let them go as high as 48 depending on age and condition of the truck. The evap could be cloogged with crap etc. 40 deg is ideal but don't kill yourself trying to get there is all I'm sayin.

 

[Turbine Doc]

Just did a evaporator 4th of July weekend on my 98 K1500 truck 2# freon was what was called for on the sticker, and GM service manual, 3# for my 98 burb with rear air, 4# is too much. Truck is cooling down to 40F on a 80F day, 52F on 95F day

 

[Acesneights1]

Just did a evaporator 4th of July weekend on my 98 K1500 truck 2# freon was what was called for on the sticker, and GM service manual, 3# for my 98 burb with rear air, 4# is too much. Truck is cooling down to 40F on a 80F day, 52F on 95F day

4 cans=48 oz/16=3 lbs
That is assuming you got every drop out of the can which you don't. There is only a small amount of pressure in those little cans, unlike a 30 lb'er. depending on what the sticker says. Every truck is different. Go by the sticker on the a/c box.You really wanna do it right you should scale the cans. Although I don't htink I know anybody that does. I scale the 30lb'er.

 

[iviper123]

i tried jumping the switch on the drier can but the clutch still engaged just like it did before even with it jumped?, so why didnt the compressor keep compressing like it should have

i think i might just replace the whole ac system, and bradn recomendations or ones to stay away from

 

[Acesneights1]

Could be a bad clutch. Check all the wiring you can, grounds etc. The control panel could be bad to. Hard to guess without being able to see it at this point. Is there any rust around the clutch ?

 

[iviper123]

theres mirerust/corrosion, nothing major on just discolered.

can i test the wires going to the clutch? to see if that is working properly

when i first turn the ac on the clutch stay on for a little while than start tho on of cycling

 

[Turbine Doc]

4 cans=48 oz/16=3 lbs
That is assuming you got every drop out of the can which you don't. There is only a small amount of pressure in those little cans, unlike a 30 lb'er. depending on what the sticker says. Every truck is different. Go by the sticker on the a/c box.You really wanna do it right you should scale the cans. Although I don't htink I know anybody that does. I scale the 30lb'er.

:thumbsup: Doh saw the count of 4 computed it as 4# , fergot 12oz/can :mad2: Scaled mine when I did it off a big R134 tank, helps to have a Brother in law works for AC&R company with all tools of trade, vac pump-free freon, and scale.

Sticker matches what is in the service manual for 1998

 

[Turbine Doc]

theres mirerust/corrosion, nothing major on just discolered.

can i test the wires going to the clutch? to see if that is working properly

when i first turn the ac on the clutch stay on for a little while than start tho on of cycling

Sounds like low freon have you jumpered the AC switch as suggested, if clutch is pulling in at all it's working electrically, now slipping or staying engaged with low pressure switch jumpered in is a different story

 

[iviper123]

if your saying low pressure switch on the drier can than yes i have jumped that switch and clutch still engaues and dis engages as before

 

[OregonHorseTug]

if your saying low pressure switch on the drier can than yes i have jumped that switch and clutch still engaues and dis engages as before

You might have a bad high pressure switch that is pulling out too soon (I don't know if this is a typical problem or not). What are your pressures when you get the cycling? I picked up a cheapo set of AC gauges from Harbor Freight just to be able to work on my various rigs. Really helpfull for diagnosing what's happening.

 

[Turbine Doc]

You might have a bad high pressure switch that is pulling out too soon (I don't know if this is a typical problem or not). What are your pressures when you get the cycling? I picked up a cheapo set of AC gauges from Harbor Freight just to be able to work on my various rigs. Really helpfull for diagnosing what's happening.

X2

High pressure while not the most common mode of cycling clutch, if orifice tube is plugged with debris could be making high pressure switch come into play( I think you could check that with a volt meter across the switch looking for it to open/close), barring that I'd pull the orifice tube to see if it's crudded up if you don't have gauges to confirm the high pressure condition.

 

[iviper123]

i got a hold of a set of gauges today i had got a a low side of 45-20 cycling
and high side of 175-275, i added more 134 and it went to 325 at its highest low side never changed, whith the ac off i got low side 60 high side 60

does anyone have a picture of the ac condenser or drawing of the ac system, i tried to unhook the condeser to check the orffice tube, but it would not budge no matter what, is there ay special tools needed?

can the condeser be put in upside down? if it is will it effect it?

 

[OregonHorseTug]

i got a hold of a set of gauges today i had got a a low side of 45-20 cycling
and high side of 175-275, i added more 134 and it went to 325 at its highest low side never changed, whith the ac off i got low side 60 high side 60

That's similar to what my readings were. I added freon (almost 2 pounds) until my low side stayed just above 30 and my vent temp would drop to 8* C (~47*F). I don't remember what my high side pressure stabilized at. My system off/balance pressure is about 75/75. How many cans of 134 did you add?

 

[iviper123]

i belive i know what the problem is, the prevoius owner had an accident and hooked up the ac system up wrong, the condenser is upside down, and the hoses are hooked up backwards. (i finally got my service book in the mail) so it should be a simple cheap fix, but i cant disconnet the hoses from the condenser!

now what!!! everthing is in good condition