a/c problem

[dksob81]

heres a new one, I am stumped on this one. my 98 jeep grand cherokee 5.9Limited a/c isn't up to par. When I got the jeep back in january the a/c didn't work so about 2 months ago I recharged the system at work, the system was completely empty, hummm thought maybe it had a leak (evap cores are a known problem in these jeeps my last jeep had a bad core) so thought maybe I will be replacing this one, well I vacuum the system down and it held vacuum great no leaks. went ahead and recharged it and the a/c worked great (in 60 degree weather...lol) but now it is getting up in the high 80's low 90's and the a/c inside the jeep will be comfortable but not cold. so today I had another a/c job I did on a truck at work, he told me about his problem (which was similar to mine) so I recovered all his freon, evacuated and recharged it to the appropriate amount (his was low) and used the thermostat in the vents and his vent air was at about 40 degree which is normal, all his pressure reading were normal aroun 30-40 on the low side and 170 on the high side.

well after I got done with his truck I took the thermostat out to the jeep and stuck it in the vent let the jeep idle for about 30 minutes with the windows up came back out to it and checked the the thermostat and it read 65 degrees (humm..... this should be way cooler then that). so I hooked it up to our a/c machine with a/c on compressor engaged the readings are about 60-70 on the low side and 250-300 on the high side, wow those reading are high, I looked at our little diagnosis card it it tells me "Air in system, Over charged" and says to "recover, evacuate and recharge system". so I recovered all the freon in the system came out with 1.52 lbs (A/C tag on jeep calls for 26 oz. which would be about 1.62 lbs) so it was a little low no big deal. I vacuumed the sytem for 30 minutes then recharged to appropriate amount (1.62 lbs) and still system reading very high (it was about 80-85 degrees outside). I recovered everything from the system again, recharged it using 1.20 lbs still same thing both reading are unusually high.

So I recovered everything again this time attempted to recover it a couple times to make sure everything is out of the system. and added 1 lbs of freon and the readings are still the same. I checked reading on a customers vehicle thinking maybe the guages were out of whack after I did the first a/c job, but their reading were fine.


What could be the problem?

[SteveB05]

I would replace the dryer and the expansion valve (orifice tube), evac and charge and see where you are. If the system had been open for any length of time, the desiccant in the dryer is likely saturated.

[dksob81]

my boss' old mechanic came in today and I told him the problem and he says that the expansion valve is prbably plugged up and would need replaced.

How do I go about replacing the expansion valve. my FSM doesn't show an expansion valve, but it does the orifice tube, form my understanding they are both the same thing. Now I went to the part store and got a new orifice tube for my jeep. but from what the book says the orifice tube is and intergral part of the liquid line (a/c low side metal line, and the entire line will need to be replaced. Is this true and where can I find the line at, i checked all my local part stores and they all have the orifice tube but it is not the entire line just the orifice itself.

[Bob D.]

Did you try putting your hand on the receiver/dryer to see if it was getting cold?
In the later model Grands the expansion valve is also a one piece, integral part built into the line..around $100.00 bucks. You may have no other option than the dealer.
Did he say if the dryer needs to be replaced also? Sometimes it's debris from a disintegrating dryer that plugs the orifice tube or expansion valve.

[dksob81]

well I checked online and found the line. Has anyone ever replaced the orifice tube in their jeep, I got an orifice tube from the part store, the thing is the book says the entire line would need to be replaced, if this is true why would the part store have an orifice tube for the jeep if you can't replace just the tube itself?

[dksob81]

Originally Posted by Bob D.

Did you try putting your hand on the receiver/dryer to see if it was getting cold?
In the later model Grands the expansion valve is also a one piece, integral part built into the line..around $100.00 bucks. You may have no other option than the dealer.
Did he say if the dryer needs to be replaced also? Sometimes it's debris from a disintegrating dryer that plugs the orifice tube or expansion valve.

I did not check the dryer/accumulator to see if it is getting cold, but I assume it is, the liquid line (Orifice tube/expansion valve line) is getting cold and sweats.

I bought an automotive heating and air conditioning book today, and it seems to be that the orifice tube/expansion valve is the problem. it states in the book "If the air tempature is higher then should be and the high side pressure and low side suction pressure are normal or slightly higher, then the expansion valve is clogged.". It also says that the low side pressure should read between 32-41 psi and the highside pressure should read between 200-260 psi, this is for my jeep - thats also what my FSM calls for.

On every A/C job I have done in the last 2 months the high side reading was around 170 or so. I just recalled one that I did yesterday a 99 dodge intrepid, this book calls for low side: 20-30 psi and high side: 210-250. my readings was about 30 and 175, but vent tempature was right at 40 degrees. I don't think anything was wrong with it because it was working great, so maybe the book isn't dead on accurate.

[SteveB05]

Readings are based on ambient and outlet temperatures. The only "accurate" way is to make sure the proper amount of refrigerant is in the system. You can troubleshoot by the gauge readings since most issues will cause an obviously incorrect reading on one or both sides.

Like I said before, I would change out the o-tube and the dryer. You don't want moisture in the system, it turns some oils into acids that will eat the evaporator.

[dksob81]

I plan on doing this soon, 2morow I am gonna call the dealership to see if they have the orifice tube in-stock, the dryer I can get at the part store.

[dksob81]

UPDATE:

Well I replaced that liquid line (orifice tube/expansion valve/ac line) today at work and it works great NOW.
Low side pressure 30-35 psi
high side pressure 180-200 psi
vent temp 30 degrees

what I did....
I recovered what freon was in the system then R&R the line, to me about 5 minutes all in all. recharged the system (1.63 lbs), then watched the guages - 42 psi (low), 175 psi (high) vent temp 40 degrees, I let the jeep run for about 15 minutes idling with a/c on, when I checked the guages at this time they read 55 psi (low), 250-260 (high) flucuating, and vent temp was up to about 49 degrees, shut the jeep off and my staic pressure was at 87 psi, at this time it was only about 60 degrees outside. DAMN, thinking that the orifice tube wasn't the problem. I decided to recover, evacuate, and recharge the system again. So I did that and when I was evacuating the system I noticed some air pockets (for about 5 seconds) HUMM I bet that was the problem. so I went ahead and recharged the system, but I only put in 1.50 lbs, this time pushing the RECIRC button (because I remember in the A/C diag. book it says to make sure outside air vents are closed) after it was filled I shut the hose for the tank off. and my guages read 30 psi (low), 180 (high) and vent temp was at about 27 degree which is very cold, never seen an R-134a system get that cold, well after idling for about 30 minutes I rechecked my reading they were still reading good, I also noticed my A/C LOW LINES and the drier start to frost up pretty good. I got in the jeep, it was like an ICE BOX. I decided to switch off the RECIRC (to allow in outside air) and when I did this I checked my reading after about a minutes of idling and the low side: 45 psi, high side: 225 psi, and the vent temp was about 40-45 degrees. and all my lines started to thaw. I let it idle for a few more minutes like this then pressed the RECIRC button again and after a few minutes the lines frosted up again, and pressure were 35 psi (low), 180-200 (high) and vent temp was at 30.. I shut everything off and checked the static pressure and it was at 65 psi (65 degrees outside/inside the shop) and the book calls for 64.0 psi static pressure at 65 degrees. So everything si working great now.


NOTE: I also had an overheating problem, while driving the temp was fine around 210 (on highway about 180) but when sitting for about 20 minutes the temp would climb up to 235, by that time I would usually shut the engine off and turn the key forward to allow the fan to run. and now I let the jeep idle for well over an hour probably close to 2 hours and it only got up to about 215.

[Bob D.]

Good deal on getting the a/c working in time for summer.

What did the old expansion valve look like?
Never heard of it happening, but it sounds like the overheating issue may have been related to the a/c problem... am I reading that right?

Anyway thanks for the update - some good info.

[dksob81]

Originally Posted by Bob D.

Good deal on getting the a/c working in time for summer.

What did the old expansion valve look like?
Never heard of it happening, but it sounds like the overheating issue may have been related to the a/c problem... am I reading that right?

Anyway thanks for the update - some good info.

Yes you are reading that correctly... the old mechanic said with my pressures being so high it would cause the engine to overheat because the excessive pressure would put more drag on the compressor and would also make the condensor hotter then normal which would get transfer to the radiator. it was only 70 degrees yesterday today it will be 90 here so I will find out for sure if that took care of the overheating problem.

We did cut the tubing and pulled the old orifice tube out just out of curiousity and it didn't look clogged, I tried to blow through the line from both ends and couldn't do it, but the screens on the tube did not looked clogged. Now it may be clogged where the orifice tube is itself (little copper tube inside the screen housing assembly).

[dksob81]

update: The a/c still works great.

The jeep was still getting hotter then I would like, it would get up to about 220-230, not quite as hot as before when it would redline, but I still wasn't comfortable with it. Now I knew it didn't have the right ELECTRIC FAN in it, because the last owner had spliced a new fan into it and it worked (got the job done) but not very efficiently. I took the fan out and hooked it up to the battery , black wire to ground and blue wire to positive, the fan worked good, but it pushed air instead of pulling it, now I know that by switching the wires this will reverse the operation of the fan so I switched them and it pulled air just fine. now the problems lied with this fan itself it is a directional fan, not bi-directional, it has a curved blade instead of a stright blade, which means it is more effective as a pusher then a puller. So I replaced the fan with a fan I had off another vehicle that just happen to be lying in the shed. And now it works great, the temp sits at about 195-200 the entire time I let it idle yesterday which was about 2 hours while the wifey was in the store shopping.......