A/C Compressor not cycling (1 Viewer)

[4lo co]

1995 FZJ80

Recently replaced most of the A/C system. Installed new compressor, condenser, dryer, expansion valve, pressure switch. Using vacuum pump, removed moisture and added freon with manifold gauges. Low side pressure was around 25 and high side pressure 275ish (maybe a little higher) with rpm's at 1500 per FSM instructions. The compressor clutch engages and air does feel cool coming out of vents but not as cold as it should. Temp drops to low 60's when driving at its lowest. The compressor never cycles and I'm not sure why. It cycled once for me randomly and the next morning when I turned it on it wouldn't cycle again.

Any suggestions on what it could be?

 

[flintknapper]

What was the ambient temperature when you were doing this and how much (by weight) refrigerant did you put in?

 

[4lo co]

ambient temp was around 90 degrees F and I added about 875g.

 

[UltraFJ40]

Just going to throw this out there. It might be of no use but I just had the same thing happen on our Honda Odyssey. Blower motor control module / resistor.

1995 TOYOTA LAND CRUISER 4.5L L6 Blower Motor Control Module / Resistor | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

 

[1972FJ55]

You might check to see that the heater valve is closed completely, it's a fairly common problem.

Adjust those heater valves!

With a record breaking heat wave in place, it's a great time to maximize your A/C performance. Thought mine worked pretty well, until we started seeing triple digit temps! Went out and found that my heater valve wasn't fully closing, and made the adjustments to the cable the other day. Here...

forum.ih8mud.com

 

[Tools R Us]

... The compressor never cycles and I'm not sure why. ...

The system cycles to prevent freeze up, maintain temperature, etc, if none of those needs exist it runs full time. Here, we have an event called summer, that makes cycling rare.

 

[4lo co]

Just going to throw this out there. It might be of no use but I just had the same thing happen on our Honda Odyssey. Blower motor control module / resistor.

1995 TOYOTA LAND CRUISER 4.5L L6 Blower Motor Control Module / Resistor | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

So in your Odyssey, the air was blowing semi-cold but no cycling from compressor and this was issue that resolved it?

 

[4lo co]

The system cycles to prevent freeze up, maintain temperature, etc, if none of those needs exist it runs full time. Here, we have an event called summer, that makes cycling rare.

lol I live in Florida so that could be a possibility but the fact it's not blowing very cold leads me to believe something i malfunctioning. My 92' 80 Series blows ice cold and will cycle on the hottest of days in Florida.

 

[UltraFJ40]

Yes, it started that way and then would only blow cool air on high. The cold completely disappeared shortly after that.

A $20 part fixed it. I am relatively clueless about AC systems so I'd defer to the experts here on Mud but that's what worked for our little van.

 

[4lo co]

Yes, it started that way and then would only blow cool air on high. The cold completely disappeared shortly after that.

A $20 part fixed it. I am relatively clueless about AC systems so I'd defer to the experts here on Mud but that's what worked for our little van.

Cool, thanks for the suggestion! I"ll test the module and see if it's faulty.

 

[UltraFJ40]

Cool, thanks for the suggestion! I"ll test the module and see if it's faulty.

Just so that you know, I did that too. No luck, it tested good.

 

[Tools R Us]

IIRC, on the '80 that resistor controls the lower fan speeds, so if all of the speeds work, it's good. How is the radiator airflow, is the fan clutch good, radiator foam?

 

[flintknapper]

ambient temp was around 90 degrees F and I added about 875g.

Your weighted amount is correct.

Your low side reading is somewhat low for that ambient and your high side pressure is somewhat high.

Typically, that combination (low side low, high side higher than normal) will point to a restriction of some type.

But...if those readings were taken immediately after the refrigerant charge (not after it has run awhile) they might be askew for that reason.

As concerns cycling....there are conditions whereby the compressor will never cycle, so I would not use that as a diagnostic tool for trouble.

 

[4lo co]

IIRC, on the '80 that resistor controls the lower fan speeds, so if all of the speeds work, it's good. How is the radiator airflow, is the fan clutch good, radiator foam?

Radiator is brand new, good airflow, fan clutch also brand new.

 

[4lo co]

Your weighted amount is correct.

Your low side reading is somewhat low for that ambient and your high side pressure is somewhat high.

Typically, that combination (low side low, high side higher than normal) will point to a restriction of some type.

But...if those readings were taken immediately after the refrigerant charge (not after it has run awhile) they might be askew for that reason.

As concerns cycling....there are conditions whereby the compressor will never cycle, so I would not use that as a diagnostic tool for trouble.

What would be examples of restrictions? Fan clutch is brand new. Condenser and radiator are brand new. Heater valve is fully shut. I'm thinking possibly evaporator not doing it's job?

 

[flintknapper]

What would be examples of restrictions? Fan clutch is brand new. Condenser and radiator are brand new. Heater valve is fully shut. I'm thinking possibly evaporator not doing it's job?

The most common 'restriction' is the TXV valve itself, next in line is the Evaporator. (TXV is attached to the Evaporator).

You did not say in your original post 'why' you replaced all the items you did? IF it was because of a compressor failure and your lines were not 'flushed' prior to installing the new parts...then debris can easily lodge at a few choke points (particularly the TXV).

Air/moisture in the system would be another reason for poor performance.

Hard to diagnose over the internet, but a second/recent reading with gauges (at a known ambient temp) would be a good starting point for us.

 

[4lo co]

The most common 'restriction' is the TXV valve itself, next in line is the Evaporator. (TXV is attached to the Evaporator).

You did not say in your original post 'why' you replaced all the items you did? IF it was because of a compressor failure and your lines were not 'flushed' prior to installing the new parts...then debris can easily lodge at a few choke points (particularly the TXV).

Air/moisture in the system would be another reason for poor performance.

Hard to diagnose over the internet, but a second/recent reading with gauges (at a known ambient temp) would be a good starting point for us.

I replaced all the items because the clutch was for sure broken on the compressor so I assumed complete failure. Prior to installing all new parts, I did flush out all the lines and the evaporator. I did make a mistake in the process of flushing. I installed the new TXV and then flushed evaporator. I figured if I flushed real good that the TXV would be fine but I know you're not supposed to flush them at all, so that may very well be the issue.

I'll go ahead and get another pressure reading here today or tomorrow and see what it reads.

 

[flintknapper]

I replaced all the items because the clutch was for sure broken on the compressor so I assumed complete failure. Prior to installing all new parts, I did flush out all the lines and the evaporator. I did make a mistake in the process of flushing. I installed the new TXV and then flushed evaporator. I figured if I flushed real good that the TXV would be fine but I know you're not supposed to flush them at all, so that may very well be the issue.

I'll go ahead and get another pressure reading here today or tomorrow and see what it reads.

Nearly impossible to adequately flush an evaporator.....owing to their design. The TXV has a screen in it that will catch most particles. You did everything right (flushed lines, replaced parts) until the evap incident.

If the original compressor failed internally...then naturally you would have had metallic particles throughout the system (hence the need to replace certain components...which you did), but even it that were not the case...it is easy to have degraded desiccant from the old drier cling to lines....later to pile up at the TXV.

Even the flushing agent itself...if not completely removed can cause issues when you recharge. So I am not saying definitively that you have a restriction or anything else, just that your initial pressure readings are somewhat suspect for the ambient temp cited.

Take the ambient temp reading from about a foot in front of the condenser when you do your next test. Let the system run and stabilize for a few minutes before recording your pressure readings. Let us know if you see any fluctuations in the gauge needles/pressures and lets go from there.

 

[4lo co]

Nearly impossible to adequately flush an evaporator.....owing to their design. The TXV has a screen in it that will catch most particles. You did everything right (flushed lines, replaced parts) until the evap incident.

If the original compressor failed internally...then naturally you would have had metallic particles throughout the system (hence the need to replace certain components...which you did), but even it that were not the case...it is easy to have degraded desiccant from the old drier cling to lines....later to pile up at the TXV.

Even the flushing agent itself...if not completely removed can cause issues when you recharge. So I am not saying definitively that you have a restriction or anything else, just that your initial pressure readings are somewhat suspect for the ambient temp cited.

Take the ambient temp reading from about a foot in front of the condenser when you do your next test. Let the system run and stabilize for a few minutes before recording your pressure readings. Let us know if you see any fluctuations in the gauge needles/pressures and lets go from there.

Sorry for the late response, been real busy recently so haven't gotten much work done on the 80. Ended up replacing expansion valve and recharging. After driving around and then hooking up gauges, low side read 30 and high side 210 at idle with ambient temp at condenser of around 85 degrees. When sitting at idle, vent temps hover around 60. In stop and go traffic, it'll dip in the mid to low 50's and driving fast has gotten me as low and 42. That's in cloudy weather with temps in the mid to high 80's. I still feel like something is off though because 60 degrees at the vent at idle seems kind of high and it takes a while for it to get down into the 40's.

 

[flintknapper]

Sorry for the late response, been real busy recently so haven't gotten much work done on the 80. Ended up replacing expansion valve and recharging. After driving around and then hooking up gauges, low side read 30 and high side 210 at idle with ambient temp at condenser of around 85 degrees. When sitting at idle, vent temps hover around 60. In stop and go traffic, it'll dip in the mid to low 50's and driving fast has gotten me as low and 42. That's in cloudy weather with temps in the mid to high 80's. I still feel like something is off though because 60 degrees at the vent at idle seems kind of high and it takes a while for it to get down into the 40's.

^^^^^

Knowing what I do about the 80 series A/C system I would say there is probably a 'little' more to be had...but not a lot.

Ultimately...it is going to come down to whether or not you are comfortable at those vent temps. IF you are...then chasing numbers is not going to be worth the return. IF you are NOT comfortable at those temps...then we need to look at two things:

1. The exact procedure you used to pump down the system and recharge it (many possible pitfalls there).
2. Ways to improve air flow across your condenser (Fan Clutch Mod and Aux Fan).

I will say that your current pressure readings are spot on for the ambient temp cited....but there are so many things we don't know about the recharging of the system. Excess oil in the system will effect the overall cooling capability, air in the system (if you didn't purge your lines, or shut off the manifold lines before shutting off the pump, didn't evacuate the system long enough, didn't use new vacuum pump oil or the wrong oil...etc, etc). All these things and more can make the difference when trying to get peak performance from the system.

You and I live in areas of High Humidity and that is your chief source of discomfort. Naturally we will want an A/C system that will cool the interior as quickly as is possible. How 'possible' that is....is dependent on the heat load at any given time (ambient temp, humidity, solar gain, cabin temp at start up).

Thankfully the 80 series uses a pretty good blower motor (OEM) and an adequately sized Evaporator. They are sufficient to service the first two rows of the vehicle pretty well (if all is working correctly). But the OEM system uses a Serpentine condenser (not as efficient as more modern parallel flow)...so that is what it is.

EVERY A/C system works by removing heat and moisture from the cabin air, this is an important fact to remember. Your A/C system (not unlike your cooling system) is big heat exchanger. So...the faster we can achieve this exchange of heat, the quicker we can reduce cabin temperatures.

Assuming a proper refrigerant charge (and little to no contaminants) then AIR FLOW is what we are after. Air flow is your friend.

We need air flow inside the cabin and air flow through the condenser. Air flow in the cabin is strictly a product of the blower motor, so a finite amount of air there. BTW I would advise everyone to drop the blower from time to time and clean the fan/wheel (some are amazingly dirty, clogged). As for the condenser, there are improvements that can be made there.

IMO, air flow into and out of the engine compartment of an 80 series is abysmal at speeds that don't create 'ram air' and even then...I consider the engine and cooling system to be 'fan dependent' when ambient temps are high.

Doing the Fan Clutch Mod will help move air across/through both your condenser (first in line) and your radiator (next in line). Also... adding an Aux Fan (for the condenser) is a proven aid for low speed performance of the A/C.

IF you have the means to do the following....we can semi-assess what measures you might wish to take:

Hook up manifold gauges, start engine, set A/C to coolest setting, blower on high, recirculate, windows up, engine at idle. Some sort of temp measuring device for vent temps.

Let the system run for 8-10 minutes to stabilize. Record the center vent temp and pressure readings.

Now take a hose and lightly 'mist' the condenser for 4-5 minutes. Watch the pressure readings to see if they fairly rapidly reduce and then check your center vent temp. Also, note IF your compressor cycles at anytime during this test (it probably will).

IF vent temps decrease along with manifold pressure and your compressor cycles sometime during this... then your system is most likely OK (even if not optimal) and I would look to improving Air Flow in order to get all that you can from the system .

But ultimately its each person's 'call' with respect to how much work they are willing to do. I always advise against 'chasing specific numbers'. Conditions are too variable to say that YOUR system isn't working correctly because you don't have the same numbers as mine. Vent temps that are 30°F below ambient are pretty good and is all that should be expected. Anything more (is sometimes possible) and all the better.