Automotive Air Conditioning Information Forum

Not sure what's going on with this car. Seemingly the cooling started suffering.

Fans running, good airflow, etc. Wish I thought to spray the condensor with the garden hose and watch the pressures.

Pressures are around 35/175. 75 degrees out, 50% humidity. Center vent only getting down to 55. @ 2000 rpm.

According to my factory service manual the low side looks a little high, and the high side a little low. Slightly overcharged maybe? But I haven't added any refrigerant lately.

Reclaim, pull a vacuum, and recharge to spec. Then repost findings.

I don't have any way to reclaim the system.

I just put the gauges on again tonight to double check. As per my manual for temp/humidity my low side is only 5-7psi above max. High side is about 100 psi below max.

I did notice tonight after a few minutes of testing the high side fitting is hot enough you don't want to touch it.

This system is all original (170k miles) as far as I know. Safe to assume it's either the compressor or a plugged up orifice tube?

If I'm going to discharge the system, I might as well flush and rebuild it all.

Nope, you are just undercharged. In fact for most complaints "my AC doesn't work as well as it used to" observations aren't needed, first thing to try is recover, evacuate and recharge. 60% of the time, it works every time

DetroitAC wrote: Tue Aug 03, 2021 5:42 pm Nope, you are just undercharged. In fact for most complaints "my AC doesn't work as well as it used to" observations aren't needed, first thing to try is recover, evacuate and recharge. 60% of the time, it works every time

Are you saying, get back to the control?

scoob8000 wrote: Tue Aug 03, 2021 5:01 pm I don't have any way to reclaim the system.

I don't have an RRR machine, either. But a local tire store close by does. So I go there whenever I need to recover refrigerant. It takes only a few minutes, they're happy to do it for me, and they gain some "free" refrigerant, which they can re-sell. Why not check into that in your locale?

scoob8000 wrote: Tue Aug 03, 2021 5:01 pm I just put the gauges on again tonight to double check. As per my manual for temp/humidity my low side is only 5-7psi above max. High side is about 100 psi below max.

scoob8000 wrote: Tue Aug 03, 2021 6:22 am Pressures are around 35/175. 75 degrees out, 50% humidity. Center vent only getting down to 55. @ 2000 rpm.

If you tested the pressures the second time at approximately the same ambient of 75 degrees, the pressures you posted aren't very far off at all. The low-side pressure of 35 PSI corresponds to an evaporator temperature of about 42 degrees. Preferably, it should be around 30 PSI to get the evap down to about 34 degrees. But center vent temps hovering at the 55-degree mark suggest that you might have some re-heating going on.

scoob8000 wrote: Tue Aug 03, 2021 6:22 am According to my factory service manual the low side looks a little high, and the high side a little low. Slightly overcharged maybe? But I haven't added any refrigerant lately.

If anything, I agree with previous comments that it's a little undercharged, not overcharged.

scoob8000 wrote: Tue Aug 03, 2021 5:01 pm This system is all original (170k miles) as far as I know. Safe to assume it's either the compressor or a plugged up orifice tube?

To check whether the compressor is pumping up to snuff, cut a sheet of masking paper (even a large paper or plastic bag will suffice), position same on the front of the condenser to momentarily block airflow, hold the engine RPM at about 1,800, turn on the A/C, and watch the high-side gauge. If the pressure rises to around 300 PSI, immediately shut off the A/C system and engine. The compressor is doing its job.

I doubt that the problem is a plugged OT, either. If it is plugged, you'd be seeing very low pressures on the low side, and it might even pull into a vacuum. Clearly, that's not the case here.

scoob8000 wrote: Tue Aug 03, 2021 5:01 pm If I'm going to discharge the system, I might as well flush and rebuild it all.

Why go through all of that work and expense if the only problem is a low charge? As said earlier, I would first recover the charge, weigh it, evacuate well, recharge to specs, then re-evaluate the pressures and cooling performance.

The specs for your car call for 28 ounces of R-134a and 8 ounces of oil--PAG-150 for a Harrison compressor, and PAG-46 for a Denso compressor.

Thank you. I'll look into a local shop to evacuate the system. Hasn't thought that one might not charge, just to recover.

I was basing my assumption of overcharge on the low side pressure. Now I see that isn't accurate.

I'll try the condensor test. Good info there and with the o-tube for future troubleshooting.

Well that was $80 at the shop wasted. $60 to recover and vacuum, $20; to recharge to factory specs. I asked what they recovered but they couldn't tell me.

Cooling feels about the same, pressures about the same.

It's 50% rh, and the accumulator is just slightly cool to the touch. No condensation on it.

My gut instinct is to discharge the system and pull the o tube. I'm betting it's black and gunky.


I did try covering the condenser to watch if the high side climbed. It did, but only to around 250.

What are the pressures now that you're sure it is charged to spec?

scoob8000 wrote: Thu Aug 05, 2021 4:52 pm Well that was $80 at the shop wasted. $60 to recover and vacuum, $20; to recharge to factory specs. I asked what they recovered but they couldn't tell me.

The suggestion was having the system recovered, not going as far as evacuation and recharging. But since that work has been completed, lets take advantage of the known, full charge, and diagnose it further by recording the pressures, center vent temps, and ambient temperature as mentioned in the post above. Do this with the engine at about 1,800 RPM, doors and windows open, system set on max cool, blower on high, and the compressor running. Post results here.

The shop should have been able to tell you how much refrigerant and oil they recovered, though. The refrigerant amount would appear on the RRR machine's front readout and the oil (if any) would collect in a graduated container on the side of the machine.

scoob8000 wrote: Thu Aug 05, 2021 4:52 pm It's 50% rh, and the accumulator is just slightly cool to the touch. No condensation on it.
My gut instinct is to discharge the system and pull the o tube. I'm betting it's black and gunky.

It's possible that the OT is clogged or partially clogged, but the low-side pressures should also reflect that.

scoob8000 wrote: Thu Aug 05, 2021 4:52 pm I did try covering the condenser to watch if the high side climbed. It did, but only to around 250.

If it was a 95-degree day and the compressor managed only around 250 PSI with the airflow blocked for a few minutes, then the compressor is weak.