Help me diagnose my AC

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brielly
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Joined: Tue Aug 11, 2020 11:26 am

Help me diagnose my AC

Postby brielly » Thu Aug 20, 2020 11:45 am

I just added the 20 oz. of r134 as per factory spec. System was vacuumed and had no leaks. This is on a 2001 jeep cherokee. My gauges read 37 on the low side and 300 on the high. The air is blowing cool but should be much colder. What's going on here? Am I overcharged or is there air in the system? Any help would be appreciated. Thanks!
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bohica2xo
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Re: Help me diagnose my AC

Postby bohica2xo » Thu Aug 20, 2020 3:46 pm

What is the ambient temperature?

Are those pressures at idle or 1800 rpm?
brielly
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Re: Help me diagnose my AC

Postby brielly » Thu Aug 20, 2020 5:52 pm

80 degree temps and pressures were at idle.
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bohica2xo
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Re: Help me diagnose my AC

Postby bohica2xo » Thu Aug 20, 2020 6:22 pm

System is either full of air, or your condenser is not doing the job.

How way it evacuated?

Any other repairs? Why was it recharged?
brielly
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Joined: Tue Aug 11, 2020 11:26 am

Re: Help me diagnose my AC

Postby brielly » Fri Aug 21, 2020 4:15 am

I replaced the condenser and accumulator. Temp was 80 outside. I vacuumed the system for 45 minutes
cmilot6329
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Location: Mesa, AZ

Re: Help me diagnose my AC

Postby cmilot6329 » Fri Aug 21, 2020 9:23 am

20 Oz looks like the correct amount for that vehicle so shouldn't be overcharged. What symptoms did you have prior to replacing those 2 things? What temp you getting at the vents? Are your fans coming on correctly? 300 high side sounds too high for 80 degree ambient temp.
brielly
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Re: Help me diagnose my AC

Postby brielly » Fri Aug 21, 2020 10:39 am

I noticed that when the electric fan comes on the high side pressure dropped into the 200's. is that normal or an indication of a problem?
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bohica2xo
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Re: Help me diagnose my AC

Postby bohica2xo » Fri Aug 21, 2020 2:19 pm

Does this vehicle have a mechanical fan and an electric fan, or only an electric fan?

Jeep has changed the fan configuration too many times to count.
brielly
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Re: Help me diagnose my AC

Postby brielly » Fri Aug 21, 2020 2:52 pm

It has both types of fan. To complicate things further the electric fan in a 2001 cherokee doesn't just come on when you turn on the AC, instead it waits until a certain temp is reached or a certain pressure in the ac is reached. I found today that the pressures with the fan on read 25 and 200 with an outside air temp of 85. The vents were only blowing 65 degrees. I guess its actually low on charge. Just for clarification, the electric fan should be running when checking pressures, right?
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bohica2xo
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Re: Help me diagnose my AC

Postby bohica2xo » Fri Aug 21, 2020 3:54 pm

Your mechanical fan clutch is shot. The mechanical fan is the most powerful air mover under the hood.

The electric fan is an add-on to help in extreme conditions and with the A/C.

Again, Jeep has changed the aux electric fan operating parameters several times over the years. Some are supposed to come on at half speed with the compressor. Some only operate at a specific high side pressure. Some are only dependent on engine coolant temperature. The Factory Service Manual is the only place with all of those answers.

But with the presence of a mechanical fan, the high side pressure should remain below 2.5x the ambient temperature when testing.

A full load test is the best way to determine system performance:

Doors open. Cabin fan on highest speed. With the gauges connected, raise the engine rpm to 1800 and hold that speed for 90 seconds. While the engine is at 1800, record the high side pressure, low side pressure, vent temperature and ambient temperature.

Post that data here.

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