AC diagnosis infrared temperatures (1 Viewer)

[dansawyer]

The vehicle is a 1997 FZJ80. The AC system performance is poor. I have tested the system with gagues and everything is within sped. Does anyone have data from an infrared thermometer? I woulld be interested in 8 readings:
The expanson valve in - 150 degrees F
The expansion valve out - 129 degrees F(on my home system this is approxamate the outlet air temp - I do not understand this reading )
The compressor in (low) ~140 degrees F
The compressor out (high) 215 degrees F
The condensor in 215 degrees F
The condensor out 150 degrees F (this appears to be way too high - I will test water on the condensor to see if that helps lower the system temp) (the performance at idle is way poorer than at 35 MPH)
The ambiant temperature at the time of the reading - 100
The air out temperature at the vents. - 70
I am trying to diagnose either fluid contamination, a bad expansion valve, or ???
The air outlet drop at 100 ambiant is 30 degrees.
It appears as though the whole system is running hot. I will try insulating the return path into the compressor. That is routed past the exhaust, I suspect it is heating the entire system.
Thank you in advance. Dan

 

[Rusty Marlin]

From past experience this leads me to think you have a blockage in the expansion valve.
But I would wait for the pros to comment before acting on that.

What were the gauge readings and at what ambient temp?
Was the low , low and the high, high, while being in spec?

 

[smritte]

Right off your high side is too low. I'm assuming your readings are correct, tested at around 1200 rpm (ish). I converted it to pressure in my head. Your Condenser inlet at that ambient should be about 220-250 psi (slightly higher with high humidity). The temp drop is about correct for that design of condenser. If you needed more temp drop there, a few guys have converted to a modern condenser and seen a bit of gain.
Right off the bat, Either your low on refrigerant (most likely) or your expansion valve is stuck open.
If your level is low, you can see high evaporator outlet temps. you don't have enough refrigerant to properly carry the amount of heat.
I normally see around 35-40 psi low side with stuck expansion valves and it drops the high side about 30-40 psi.
I tend to use IR thermometers to check to see if the temp is even across something, I never use them for accuracy. I use a conduction type probe into my thermometer.

 

[dansawyer]

Right off your high side is too low. I'm assuming your readings are correct, tested at around 1200 rpm (ish). I converted it to pressure in my head. Your Condenser inlet at that ambient should be about 220-250 psi (slightly higher with high humidity). The temp drop is about correct for that design of condenser. If you needed more temp drop there, a few guys have converted to a modern condenser and seen a bit of gain.
Right off the bat, Either your low on refrigerant (most likely) or your expansion valve is stuck open.
If your level is low, you can see high evaporator outlet temps. you don't have enough refrigerant to properly carry the amount of heat.
I normally see around 35-40 psi low side with stuck expansion valves and it drops the high side about 30-40 psi.
I tend to use IR thermometers to check to see if the temp is even across something, I never use them for accuracy. I use a conduction type probe into my thermometer.

The numbers are degrees F. I edited the post to make it clearer. Thanks for your reply.

 

[smritte]

I assumed Fahrenheit.

 

[jpoole]

the performance at idle is way poorer than at 35 MPH

Your water on condenser will help shed light on this but your fan clutch may not be moving as much air as you want at idle. That being said sounds like some real expert insights above and like you have larger problems to look into before you worry about tuning your fan clutch for a little idle performance improvement.

 

[flintknapper]

The vehicle is a 1997 FZJ80. The AC system performance is poor. I have tested the system with gagues and everything is within sped. Does anyone have data from an infrared thermometer? I woulld be interested in 8 readings:
The expanson valve in - 150 degrees F
The expansion valve out - 129 degrees F(on my home system this is approxamate the outlet air temp - I do not understand this reading )
The compressor in (low) ~140 degrees F
The compressor out (high) 215 degrees F
The condensor in 215 degrees F
The condensor out 150 degrees F (this appears to be way too high - I will test water on the condensor to see if that helps lower the system temp) (the performance at idle is way poorer than at 35 MPH)
The ambiant temperature at the time of the reading - 100
The air out temperature at the vents. - 70
I am trying to diagnose either fluid contamination, a bad expansion valve, or ???
The air outlet drop at 100 ambiant is 30 degrees.
It appears as though the whole system is running hot. I will try insulating the return path into the compressor. That is routed past the exhaust, I suspect it is heating the entire system.
Thank you in advance. Dan

Dan...trying to use a Subcooling/Superheat method to determine system performance with an IR temp gun.....is going to be inaccurate and unnecessarily complicated. (the reason A/C shops DON'T do it).

Get an analog or digital vent temp gauge. Use your manifold gauge set and tell us what your high and low side pressures are along with ambient temp at time of testing and vent temps.

The trouble with using an IR temp gun on light colored and reflective surfaces (like your compressor and aluminum lines) is one of Emissivity. You would need to use conductive clamps and a 'good' meter to take accurate measurements if you are going to check your SC/SH. That method is appropriate (indeed the standard) for residential/commercial HVAC work.....unnecessary where we are concerned here.

So please post your gauge pressures (PSI) and let us help you decide what was in 'spec' or not. Your IR gun can be used in certain places to help detect restrictions, but honestly.....the gauges and simply reaching down and touching the lines/components will tell you the same thing.

We need a 'starting point'.....so get us the pressures first and ambient and vent temp.

 

[dansawyer]

Dan...trying to use a Subcooling/Superheat method to determine system performance with an IR temp gun.....is going to be inaccurate and unnecessarily complicated. (the reason A/C shops DON'T do it).

Get an analog or digital vent temp gauge. Use your manifold gauge set and tell us what your high and low side pressures are along with ambient temp at time of testing and vent temps.

The trouble with using an IR temp gun on light colored and reflective surfaces (like your compressor and aluminum lines) is one of Emissivity. You would need to use conductive clamps and a 'good' meter to take accurate measurements if are going to check your SC/SH. That method is appropriate (indeed the standard) for residential/commercial HVAC work.....unnecessary where we are concerned here.

So please post your gauge pressures (PSI) and let us help you decide what was in 'spec' or not. Your IR gun can be used in certain places to help detect restrictions, but honestly.....the gauges and simply reaching down and touching the lines/components will tell you the same thing.

We need a 'starting point'.....so get us the pressures first and ambient and vent temp.

Thank you. I was hoping the temp measuring method might add some insight over the gauge / temp data. The first readings at 82 degrees ambiant are:
2000 rpm
low 20
high 200
outlet temp 58
(the high pressure varies significantly from a low of 180 for a high of 320 - the change is slow over 20 to 30 seconds )
follow up - After researching symptoms this would indicate a blockage some where after the compressor, most likely either a clog in the expansion valve or a clog in the dryer. Is there a way to differentiate between these?

 

[flintknapper]

Thank you. I was hoping the temp measuring method might add some insight over the gauge / temp data. The first readings at 82 degrees ambiant are:
2000 rpm
low 20
high 200
outlet temp 58
(the high pressure varies significantly from a low of 180 for a high of 320 - the change is slow over 20 to 30 seconds )
follow up - After researching symptoms this would indicate a blockage some where after the compressor, most likely either a clog in the expansion valve or a clog in the dryer. Is there a way to differentiate between these?

Before we do that....take the readings again at engine idle, there is no reason to elevate the engine rpm to 2,000 rpm and even the FSM recommendation of 1500 is unnecessary except to first stabilize the system. Your idle (if working correctly) will automatically kick up to 900-1000 rpm when the compressor is running. This simulates 'real world' conditions when you are at a stop light or in heavy stop and go traffic (the worst possible situation for A/C).

So if you don't mind, take the readings again at normal idle, post here. Note any fluctuation and record that too. Then we can move forward. Has any A/C work been recently done on the system....or has this issue just started?

 

[dansawyer]

Before we do that....take the readings again at engine idle, there is no reason to elevate the engine rpm to 2,000 rpm and even the FSM recommendation of 1500 is unnecessary except to first stabilize the system. Your idle (if working correctly) will automatically kick up to 900-1000 rpm when the compressor is running. This simulates 'real world' conditions when you are at a stop light or in heavy stop and go traffic (the worst possible situation for A/C).

So if you don't mind take the readings again at normal idle, post here. Note any fluctuation and record that too. Then we can move forward. Has any A/C work been recently done on the system....or has this issue just started?

Yes.
Ambiant - 90 degrees
low pressure 38
high pressure 240
air outlet - 64
idle rpm about 850
readings are steady
There were no major changes to the system. I did add some R134a. (based on the above perhaps too much.) In years past I have seen output air vent temps in the 38 to 45 degree range. 65 is a long way from those readings.

 

[Rusty Marlin]

 

[Rusty Marlin]

Low pressure.
Where's the leak? that's the next question that needs to be solved.

 

[flintknapper]

Yes.
Ambiant - 90 degrees
low pressure 38
high pressure 240
air outlet - 64
idle rpm about 850
readings are steady
There were no major changes to the system. I did add some R134a. (based on the above perhaps too much.) In years past I have seen output air vent temps in the 38 to 45 degree range. 65 is a long way from those readings.

Good....thank you.

Vent temp was measured with?

I agree there are some gains to be had. Let's start with adding some refrigerant (about 1/2 can) and monitor both your vent temps and gauge readings. See if increasing the refrigerant charge (bringing low side up to mid 40's and high side to 260psi) results is lowering the vent temps at least 5-6°F.

If at any point your pressure readings exceed the above AND there is no improvement in vent temps....STOP. Let us know what you get. I'd also like to see you 'mist' the condenser and note the pressure drop and vent temps is you are equipped to do that.

 

[dansawyer]

Good....thank you.

Vent temp was measured with?

I agree there are some gains to be had. Let's start with adding some refrigerant (about 1/2 can) and monitor both your vent temps and gauge readings. See if increasing the refrigerant charge (bringing low side up to mid 40's and high side to 260psi) results is lowering the vent temps at least 5-6°F.

If at any point your pressure readings exceed the above AND there is no improvement in vent temps....STOP. Let us know what you get. I'd also like to see you 'mist' the condenser and note the pressure drop and vent temps is you are equipped to do that.

Thank you. OK things have stabalized. I added the remainder of the can I had been using. It is was probably closer to a quareter of a can.
New Readings
Ambiant - 95 degrees
Low Pressure 30
High Pressure 150
RPM ~900
Air output temp - 66
spraying with water causes the low pressure to drop from 30 to 20, the high goes down perhaps 5 psi, and the output air to actually go up a few degrees
Reving the engine to 2000 causes the low to go down to 15, again with only minor changes in high repssure. The ouput air drops to 60.

 

[flintknapper]

Thank you. OK things have stabalized. I added the remainder of the can I had been using. It is was probably closer to a quareter of a can.
New Readings
Ambiant - 95 degrees
Low Pressure 30
High Pressure 150
RPM ~900
Air output temp - 66
spraying with water causes the low pressure to drop from 30 to 20, the high goes down perhaps 5 psi, and the output air to actually go up a few degrees
Reving the engine to 2000 causes the low to go down to 15, again with only minor changes in high repssure. The ouput air drops to 60.

You're still low on your refrigerant charge. Do you have more that you can add?

 

[dansawyer]

Yes. I added between 1/3 and 1/2 a can. At 87 ambiant the low side went to 40 and the high side went to the 250 range at idle. The outlet temp dropped to the 58 range and idle. A road test was very satisfactory.
(The onliy bad news is the high pressure caused a small leak in the high side on my gauge set. )
Thanks for your help.

 

[flintknapper]

Yes. I added between 1/3 and 1/2 a can. At 87 ambiant the low side went to 40 and the high side went to the 250 range at idle. The outlet temp dropped to the 58 range and idle. A road test was very satisfactory.
(The onliy bad news is the high pressure caused a small leak in the high side on my gauge set. )
Thanks for your help.

De Nada.

Keep an eye on it. IF you only have a 'slow' leak (requiring a seasonal topping off) then I don't recommend chasing it down, just not worth it. On the other hand....if you lose refrigerant more quickly....then of course, you'll need to find the leak.

Good work Sir!