1998 4runner Intermittent AC

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MK_98

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As the title says having some issues with my AC. Drive a 1998 4runner 4wd 5vz-FE. Driving to work in the morning the AC works fine blows cold entire drive to work, but on my way home it doesn't work. I can hear the compressor turn on and then immediately turns off again and will do this about every 10-15 seconds? Its about 70-80 degrees in the morning and over 100 on my way home this past week and it started doing this Monday.

Doing some searching 4th gens seem to have a pressure switch issue but I haven't found anything in the 3rd gen model year.
 
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Check the pressures on the low and high sides. Start there first.

If the pressure is OK, then the compressor (bearing or clutch) may be on its way out.
 
Yes, check for the freon. Look for any bubble formation under the glass window located on top of the AC filter located right after the AC compressor.

If you have the right amount of freon, with the AC compressor clutch on, you will see clear (no bubbles) under the glass window. Soon after the AC clutch disengages, you'll notice bubble formation and immediately it should clear out. The cycle repeats with the clutch.
 
Think I've got it figured out. The ac is overcharged its just barely before the overcharged line when its cooler out when its 110 at 5:00 the gauge reads overcharged
 
Check Yur thermostat too.. Maybe partly malfunctioning to never go red in temp gauge but onky little above normal half way.. Then shuts off signal to ecm to compressor.. Cools down, then thermostat temp gauge sends signal ok.. Them ecm turns ac compress on signal.. If everything else is ok first.. I had that problem on my 2005 toyota sienna van.. Ac guy couldn't figured it out,, finally found answer from forum guy who saids dealer replacement thermostat and fixed... Remember cooling, radiator, sensors are also part of ac system.. When ecm sense car temp hot.. It turns ac compressor off to save compressors atleast what I was told..
I know, weird fix, but it worked.. All temp related,, reason why it works in morning cool time
 
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Honda pc said:
Check Yur thermostat too.. Maybe partly malfunctioning to never go red in temp gauge but onky little above normal half way.. Then shuts off signal to ecm to compressor.. Cools down, then thermostat temp gauge sends signal ok.. Them ecm turns ac compress on signal.. If everything else is ok first.. I had that problem on my 2005 toyota sienna van.. Ac guy couldn't figured it out,, finally found answer from forum guy who saids dealer replacement thermostat and fixed... Remember cooling, radiator, sensors are also part of ac system.. When ecm sense car temp hot.. It turns ac compressor off to save compressors atleast what I was told..
I know, weird fix, but it worked.. All temp related,, reason why it works in morning cool time
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Ill check those, idk if the thermostat has been replace it has a sticker saying timing belt was done 40k ago. I guess they could of not done everything else? I checked the temp gauge its just below half as always
 
MK_98 said:
Previous owner said he did it himself, I haven't had any issue with the ac till it got over 100 out so didn't think anything of it
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Most pressure charts are not detailed enough to allow for variations in both humidity and temperature so under and overcharging will happen if conditions are not ideal. I have used this one that covers most conditions with good results:
 

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TheDurk said:
Most pressure charts are not detailed enough to allow for variations in both humidity and temperature so under and overcharging will happen if conditions are not ideal. I have used this one that covers most conditions with good results:
Click to expand...

On that chart, is the "discharge temp" the expected air temp at the vents? Or is it referring to something else? If it is the vent temp — shouldn't r134 be warmer than the old r12? I'd always heard that r12 was better/colder than the new stuff.
 
StreetCreeper said:
On that chart, is the "discharge temp" the expected air temp at the vents? Or is it referring to something else? If it is the vent temp — shouldn't r134 be warmer than the old r12? I'd always heard that r12 was better/colder than the new stuff.
Click to expand...

Good question. I heard the same. I have never looked at that column. But yeah, Discharge Temp is vent temp (doors open, recirc., Fan High) On R-134a, it is surprisingly accurate.

My last R-12 was my 1885 e23 735i.
 
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