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High High side pressure

turkey72 on Tue May 27, 2008 6:33 PM User is offline

Year: 1999
Make: Jeep
Model: Grand Cherokee
Engine Size: 4.0
Refrigerant Type: r-134
Ambient Temp: 85
Pressure Low: 25-28
Pressure High: 300 plus
Country of Origin: United States

I have a 1999 Jeep Grand Cherokee Laredo ( non-auto climate control) and I am having excessive high side pressure while the compressor is kicked in then it drops right back down. Its normal on the low side and at about 230 on the high side until the compressor cycles then it spikes quickly, till the high pressure switch kicks in. The compressor quick cycles, it hold almost 30 in for over an hour. It has the tow package with the mechanical cooling fan, it runs 210 while at idle no matter no matter how long it idles, so its not over heating. Even when I drive it, the air never gets colds. Im wondering if the orifice tube could be clogged. I used stop leak last year in it. Could the evaporator be clogged?? The only time it spikes is when the compressor cycles. Any ideas, suggestions would help as its getting hot here and I have Black leather!! Ha ha

Edited: Mon June 09, 2008 at 1:41 AM by turkey72

TRB on Tue May 27, 2008 7:27 PM User is offlineView users profile

Things that come to mind, poor air flow, over charged, sealer in the system, restriction and maybe to much oil.


When considering your next auto A/C purchase, please consider the site that supports you:

turkey72 on Tue May 27, 2008 8:52 PM User is offline

I did put stop leak in at the end of last year. I used the prefilled recharge containers with the oil already in it. Fan clutch seems to be working good, never overheats or runs hot, always within operating range. Restriction? what are you thinking?? Orifice?? Evaporator? Condenser?? Just looking at all my options before diving into the dash to change the evaporator, hoping its something else. Grand Cherokee's are one of those that aren't fun!!

mk378 on Tue May 27, 2008 10:37 PM User is offline

You need a lot more air from the fan for the A/C to work well than it takes just to keep the engine at normal temperature. Try misting water on the condenser to cool it and see if the pressure comes down and it starts working better. Is the suction line cold at all?

If you have a blockage the low side typically goes lower than normal or even negative. Unless the compressor is also not pumping well.

If you must open the system it's a big can of worms with that sealer. Total replacement may be necessary

turkey72 on Wed May 28, 2008 10:46 AM User is offline

Ok,I updated the info,the low side was at 20,not 35. That is all it would take before it would start spiking on the highside. The pipe that was supposed to get cold never did.I drove it around for awhile and nothing changed. Before it got cold last year it blew ice cold just would bleed down after a week or so, even after the stop leak.I tried using it this year and nothing so I decided to replace all seals and orings and I found which one was leaking.That is when all this started. We pulled vacume, tryed filling it and this is where I am. As far as stop leak in the system, what all can it plug up? Like I said it worked fine after installed stop leak last year just didnt fix the leak.

HECAT on Wed May 28, 2008 11:09 AM User is offline

There are sealers that will crystallize when exposed to air and moisture (supposedly at the leak area). They remain in liquid form in the system until they find the leak (again supposedly). When you opened the system to repair the leak by installing new seals, the sealer laying in the system may have crystallized. This type of sealer cures quickly and it is always recommended that if a sealer is suspect to be in a system; proper system flushing must be performed immediately upon opening the system if you are going to have any chance of recovering and reusing components. This product may have crystallized in the bottom half of the condenser blocking pathways, which can cause high head pressure; or may have crystallized partially in the orifice creating back pressure. You may not have used this type of sealer, and this is only to answer "what can happen". This is also why professionals have called such products "Death Kits".

I would not rule our air flow and the misting test should be done; and a new OE clutch fan may be in order.

I would recover and take a look at the o-tube/TXV screen for debris/sealer junk.


HECAT: You support the Forum when you consider for your a/c parts.


Edited: Wed May 28, 2008 at 11:10 AM by HECAT

turkey72 on Wed May 28, 2008 11:24 AM User is offline

The best I remember it was an Interdynamics brand sealer. Im gonna do the mist test and see what happens. If my fan clutch was bad would driving down the highway at highway speeds create enough airflow to cause it to cool?? Would or could that stuff clog or restrict the evaporator and cause this problem? ?? Just hoping to eliminate that component cause I REALLY DONT want to take my dash out!!!Ha Ha

turkey72 on Wed May 28, 2008 11:29 AM User is offline

The high side pressure runs at about 220 until the compressor engages then spikes very high and then immedietly drops back down to around 220 as soon as the compressor disengages.

Chick on Wed May 28, 2008 4:33 PM User is offlineView users profile

Sounds like a restriction or a lot of air in the system..A restriction is likely since you added sealer, but if you just added refrigerant, could be air in the system, but doubtful.. I would have it recovered and recharged, that will show the tech if there is a restriction. But please tell whoever does it that there is sealer in the system...

Email: Chick


Freedoms just another word for nothing left to lose

turkey72 on Thu May 29, 2008 1:17 PM User is offline

I haven't done the mist test yet but this morning I drove about 2 miles and turned the AC on and it started to blow cold, I pulled over the hoses were cold.As soon as the Jeep started to warm up things started blowing warm. Could that fan clutch be faulty?? I know someone said that before and it makes a since as soon as the compressor engages and cycles the freon, if the fan isnt working properly and not cooling the condenser?? Any thoughts??

Edited: Thu May 29, 2008 at 1:26 PM by turkey72

mk378 on Thu May 29, 2008 1:29 PM User is offline

If it blows cold until the engine warms up you also have the possibility that the heater and A/C are fighting each other, because the heater does not shut down like it should when you set the temperature control on the dash to cold.

The A/C hoses will still be cold under that condition.

turkey72 on Thu May 29, 2008 2:01 PM User is offline

I have the manual control for the AC not the auto one. I moved it while the ac was cold and it went right to warm and as soon as I went back to cold it was cold again. The AC lines went to warm as I let it idle. That why im leaning to the tips earlier to look at the fan clutch. It never roars anymore. Again the only time my high pressure spikes is when the compressor engages then it comes right back down, we checked it when the vehicle was idle for about 15 minutes so it was definetly warm. Again, I havent done the mist test yet.

turkey72 on Thu May 29, 2008 2:04 PM User is offline

We pulled a vacuum on the system before we added the freon. Will that get rid of the trapped Air

TRB on Fri May 30, 2008 12:41 AM User is offlineView users profile

Originally posted by: turkey72
We pulled a vacuum on the system before we added the freon. Will that get rid of the trapped Air

Normally if the evacuation procedure is done correctly, air in a system is removed. If only one side is open and you have a restriction then there is an opportunity that air could be left behind.

When considering your next auto A/C purchase, please consider the site that supports you:

turkey72 on Wed June 04, 2008 6:18 PM User is offline

UPDATE: Clutch fan freewheels and never gets firm, I was looking at it and deep inside the shroud there is a electric fan. Turned on the AC and it didn't spin. Though maybe that it was something to do with the ac having high high side pressure during compressor engagement. Anyway I jumped it directly to the battery and still doesn't work. I think I found my high high side pressure problem. No airflow. what do you all think. I have a new fan clutch that is going on when I change the electric fan? Thanks!

Chick on Wed June 04, 2008 6:30 PM User is offlineView users profile

Yes, no fans will do it.. But after fixing the airflow problem I would have it evacuated and recharged to fatory specs..

Email: Chick


Freedoms just another word for nothing left to lose

turkey72 on Fri June 06, 2008 1:43 PM User is offline

Ok, I changed the fan clutch and the electric fan. The Jeep now runs cooler. back down where it belongs. Electric AC fan now comes on also when the AC is turned on. Ok, Should be ok...Right?? Well pressure on the low side is 35 on the low side. Haven't been to my friends house to check high side yet but anyway the high side line going into the evaporator is COLD, and coming out.........warm, nothing!! Is my evaproator clogged up??? Its cold going in,warm coming out. Shouldn't it be cold coming out also?? It seems like that is a restriction in there . Any help here!! Thanks everyone for responding!!

mk378 on Fri June 06, 2008 1:59 PM User is offline

Like Chick said, now make sure your charge is correct. The only way to be sure is to take it all out and put back the specified amount by weight.

Yes lines should be cold coming out of the evaporator too. The high side line should not get cold until after the OT (at which point, it technically becomes a low side line), though on many vehicles the OT is mounted near the condenser.

turkey72 on Fri June 06, 2008 2:07 PM User is offline

I see where its crimped and its cold after that. Its crimped right after the condensor. Its cold after that and going into the firewall. Then coming out warm. Wouldn't that indicate a restricted evaporator? Just the warm line coming out indicates a restriction in the evaporator. Man I don't want to yank my dash out but its looking that way!! Does it sound that way to anyone else?? Like a restricted

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