AC Issue - Fast Compressor Cycling

Hello all,

My 4runner has been having AC problems. Initially, when driving >1 hour, the AC would start blowing cold air. I recently had the fan clutch replaced (in an attempt to fix this). I had cold AC for a few days then it dropped off. Yesterday I was getting hot air within 10 minutes of driving, which is worse than it has ever been.

Since it got worse the past few days, I am wondering about a leak, however, I have previously tried using UV dye, but I could not see anything.

The major symptom I have right now is fast compressor cycling. The compressor stays on for a maximum of 3 seconds.

I have read that fast cycling can mean overcharging, but I can't see how that would happen when it was working better before. Can it also indicate undercharging?

 

First attach an OBD scanner and see if it showing any fault codes. If there are none for the AC at least, my next step would be to check the AC pressure switch but this requires that you have access to a pressure gauge. I suspect by connecting a pressure gauge you should also be able to eliminate faulty compressor and/or leaks. In theory the sight glass can also be used to detect leaks but I have had a spotty luck with the AC sight glass.

 

Ahdofu,

I am not getting any fault codes. I only have the dinky gauge for refilling, so I can only read the low line. It goes from 25 psi when the compressor is off(?) to 45 psi when the compressor is on(?). Last night when it was warmer, it was going from 45 psi to 65 psi. I tried adding r134a and it didn't change the symptoms at all.

Another symptom I forgot to mention is that the place where water drips out of the evaporator has a very steady drip, more so than I have seen on another 4runner which seemed to have perfectly fine AC.

 

I was expecting the high side pressure to read something larger than 65 psi. Doing a google search it says it may be around 225-250 psi. I am baffled as to why the evaporator would have a steady drip as that means condensation is happening around the coil because of cooling and yet the circuit does not look like to be operating with enough pressure.

 

I may have not made it clear. I can only measure the low pressure side, but it is fluctuating between 45 and 65

 

Expansion valve. If it’s holding pressure than the expansion valve. I would take it in to the shop so they can cycle the refrigerant, check for leaks. And you can clean the evaporator core.

 

My bad for misunderstanding. I think the low pressure side is typically around 30 psi. Seems either there is too much refrigerant or the evaporator is not doing its job during the expansion process. Without additional data it is hard to tell what is going on. I agree with SR5 Limited. It is time for a shop visit.