Automotive Air Conditioning Information Forum

I have a '96 explorer 5.0. I bought it a few years ago and I replaced absolutely every part in the AC and cooling systems at that time.
I bought the heavy duty radiator, fan clutch and 180 degree thermostat.
I bought the smart vov orifice tube too.
I recently recharged the system. My gauges read 50 inHg Low and 148 inHg High at 85 Deg F.
The only odd thing I noticed is that the clutch does not cycle. When I switch the AC on, the compressor clutch engages and stays engaged until I switch it off.
The system seems to perform well when I am on the freeway. The other day, my outside temp showed 102 deg F and I saw AC temps in the low 40s at the vent. However, when I would stop at a stoplight, the vent temp would go up to 80 deg f. This is very repeatable.
The engine coolant temp is never a problem. It hardly gets off the peg no matter what the outside temp.
The engine fan does seem to be pulling a moderate amount of air when I open the hood. It does not seem to be blowing my hair back like I have seen with some cooling fans.
It seems like this car is in desperate need of an electric cooling fan to come on when I turn on the AC, but it never came with one.
I cant imagine that the AC performed this way when new, but I cant figure out what I have done wrong.
Any ideas?

Why was the system recharged?

What process did you use to get the correct charge weight installed?

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bohica2xo wrote:Why was the system recharged?

What process did you use to get the correct charge weight installed?

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I recharged the system because I was not getting much cold air. By this I mean that there was a significant delay between when I would switch on the AC and when I would start to feel cold air. Even then, I never saw temperature at the vent below about 60 degrees F and this was only on the freeway.

I did not weigh the refrigerant that I added. I purely went by gauge pressures. Before I added R-134, my pressures were 28 inHg Low and 90 inHG High at 75 degrees f. I think I added about 17 ounces (one 12 oz can that was about 1/3 full, one 3 oz can with dye, and about 5/6 of a 12 oz can). I am estimating the amounts. I did not weigh the cans.

I had a hard time figuring out what pressures I should be seeing. I could not find what I thought of as a reliable source for what my pressures should be. In the end, I used a the chart from A/C pro which shows (at 85 deg f) 45-55 inHG low and 225-250 inHG High. I am puzzled by the fact that am now right in the middle of this spec on the low side (50), but I am way low on the high side (150).

You can not charge a system by pressure. It is not a tire you can air up or down for better performance.

Pressures are used for diagnostics, and your issues would appear to be a significant undercharge & a worn out fan clutch.

The correct charge weight for your vehicle Is 26 ounces of refrigerant and 7 ounces of oil. If you had installed the correct charge your high pressure would be significantly higher, provided the compressor is in good shape. Only a full charge will give useful pressure data.

Recover whatever refrigerant that is in the system. Evacuate it then charge the full 26 ounces of refrigerant. Then test at idle, record the high & low pressures. Raise the engine rpm to 2000+ RPM, cabin fan on high, both front doors open. Record the pressures after running at that speed for 1 minute, while the RPM is still over 2000.

Post the pressure results here.

bohica2xo wrote:You can not charge a system by pressure. It is not a tire you can air up or down for better performance.

Pressures are used for diagnostics, and your issues would appear to be a significant undercharge & a worn out fan clutch.

Wow, thanks for the quick reply.

When I replaced the entire system a few years ago, I was meticulous about weighing the refrigerant and everything seemed to work well back then. So I assume I have some sort of a leak now. Are you saying that after a leak, one must always evacuate the system and recharge with the full amount?

Since the fan clutch is only a few years old, I find it hard to imagine that it is worn out. Is it possible that my 180 degree thermostat keeps it from engaging? It puzzles me that engine coolant temp is just never a problem.

Modern cars don't overheat with completely dead fan clutches, but the condenser airflow takes a big hit.

Yes, you need to have the full charge in a system to evaluate it. Your high side reading is low, but that could be low charge or poor compressor performance.

Fan clutches wear out. Sometimes aftermarket units are done after two years here in the desert. The freeway performance points to an airflow issue.

The 180f thermostat is probably a little cold, the OEM was a 190 or 195. This can cause the gauge to read a little low, and the EFI to run a little richer. Not a big thing really. Plenty of heat there to lock up the fan. I would avoid running a 160f thermostat on any computer controlled car.