Overheating issues

[IBoughtASupra]

I still believe the problem is with the condenser not being cooler or your compressor, we have installed multiple compressors that were remanufactured and found then to be defective.

Either try a new compressor or have the car sit and idle and spray and keep spraying cold water on the condenser to see if it drops the high side and the vent temperatures get lower while idling.

 

[CyFi6]

What inclines you to think it is the compressor? How could a bad compressor produce pressures as high/low as it does? I will try spraying the condenser, but I don't honestly see how I can get any more airflow through it.

I guess now my only interest is how to improve the stock system, the way it sits now is just not working out.

For instance, today it is about 108* outside, and after class when I got in my car the interior was 140*. I opened the windows, let it air out etc turned the ac on high and took off after a couple minutes. My drive home is 10 minutes, and the average temp out the vents with blower on high and vent on recirc was ~68 degrees. Lowest I saw was 65 and that was during steady cruise. Since about half of my drive home is idling, my vent temps would rise to 72, and after driving off it takes a good 2 miles just to get back down to 65. When it is 100+ outside and easily 110+ inside the car, 70 degree air doesn't do jack.

Where do I even start? As long as the evaporator and compressor are sufficient, retrofitting the other parts of the system with beefier components probably would be feasible, I just have no idea where to start with it all.

 

[IBoughtASupra]

I am not trying to get air through the compressor, the spraying of water on it, cold water, will help cool it down. You would see the effect of the cold water on the condenser if you had a gauge hooked up to the high side.

As you are spray the condenser with cold water, don't be greedy, soak it down and go inside and see if the temperature at the vent got any cooler. If it did, two things, a bad condenser, but you replaced it, so next would be not enough air passing through it.

The compressor theory is based on our shop's experience remanufactured compressors. It could be a defective one.

Did you read my post on the Maxima that had the SAME problem your car is having? You are getting cold air, the maxima wouldn't and the compressor was running. We changed every component, and I mean everything. Nothing was left to get changed besides the belt that was turning the compressor. The issue? It was the expansion valve. It was replaced twice but it came with a screw for adjustment and it was misadjusted so it would not open at the correct pressures. We had to play with the adjustment on the valve, a little screw that controlled a ball and spring, until it opened at the right pressure and then bam, super cold A/C. Check your expansion valve if you have the old one out, does it have any adjustment?

 

[CyFi6]

If it did, two things, a bad condenser, but you replaced it, so next would be not enough air passing through it.

Thats what I mean, I can't think of any way to increase airflow through the condenser any more, I have already done as much as I can for airflow.

Did you read my post on the Maxima that had the SAME problem your car is having? You are getting cold air, the maxima wouldn't and the compressor was running. We changed every component, and I mean everything. Nothing was left to get changed besides the belt that was turning the compressor. The issue? It was the expansion valve. It was replaced twice but it came with a screw for adjustment and it was misadjusted so it would not open at the correct pressures. We had to play with the adjustment on the valve, a little screw that controlled a ball and spring, until it opened at the right pressure and then bam, super cold A/C. Check your expansion valve if you have the old one out, does it have any adjustment?

Yeah there is an internal adjustment on the TXV, but getting it adjusted requires evacuation and full removal of the evap core. You may be onto something as it still seems to be a metering device issue, but how in the world would I ever know how much to adjust it? I assume the adjustment needs to be backed off to allow more refrigerant into the evap. Keep in mind every time I have to evacuate/charge I gotta drive about 30 minutes to my shop. Thanks for the help, maybe there really is something wrong with my system contrary to what the shop says.

 

[3p141592654]

With 10 deg subcooling there is already plenty of liquid in the condenser. Spraying it with water will just add more liquid in the condenser, won't change a thing at the evap.

 

[IBoughtASupra]

With 10 deg subcooling there is already plenty of liquid in the condenser. Spraying it with water will just add more liquid in the condenser, won't change a thing at the evap.

No no, that's not my point. I am saying if the condenser is not doing an adequate job of cooling the refrigerant, then the EVAP will not have cold refrigerant. A quick way to test if air flow is the problem is to just soak it down with cold water. If it starts to blow cold on the inside after soaking it, then we know the problem is insufficient cooling of the condenser.

Here read this....
http://macsworldwide.wordpress.com/...alves-and-orifice-tubes-keep-your-ac-flowing/

 

[CyFi6]

With 10 deg subcooling there is already plenty of liquid in the condenser. Spraying it with water will just add more liquid in the condenser, won't change a thing at the evap.

But why are my high side pressures so far out of specs?

 

[3p141592654]

We've gone down this path before. High hi-side and low lo-side is an obstruction. You've now replaced the TXV and the whole evap, so that should have covered any of the usual culprits. Unless you've got a bolt or something stuck in the pipe, or a big dent somewhere, I don't know where else to look.

In my home AC I had a piece of duct tape float through the system and end up at the TXV screen. The high side pressure was so high the compressor went into thermal overload and shutdown (no high pressure trip on most residential AC systems).

The cooling power of an AC system comes from the latent heat of vaporization (167kJ/kg for R12), which is a 167 times the specific heat capacity of the refrigerant (0.9 kJ/kgK for R12). This is why all you need is liquid in the line, you don't really care about its temperature too much, as it is not a major driver for system capacity. Subcooling confirms you've got some fraction of the condenser with liquid, and that is all that is needed.

 

[IBoughtASupra]

But why are my high side pressures so far out of specs?

That can also be caused by a insufficiently cooled condenser.....

 

[CyFi6]

So with the AC on high/recirc./windows open/hood open it was blowing about 60*f from the vent (cooler out today, and it was only about 10 AM). Bubbles apparent in sight glass (idle), drenched the condenser for about 3 mins and the vent temp dropped to about 52* and no more bubbles in the glass, liquid line cool to the touch (never gonna get this cool with airflow alone). After cooling the condenser off thoroughly, the vent temp stayed 52 the whole way home, dipping to around 49 or 50 with steady state driving 45mph.

It almost seems like once I was able to get rid of the initial heatsoak, the system could keep up. Same thing happens when I have the car in the garage overnight, the AC works well first drive of the day, but after being outside in the sun, being driven around etc, it gets warm vent temps.

There are definitely no internal restrictions in the system (assuming my brand new components are not restricted). The ONLY lines that were not replaced were the suction line along the front of the condenser, the suction line along the pass side engine bay, and the liquid line along the passenger side engine bay, and all of these were thoroughly flushed/blown out with compressed air. Theres no kinks anywhere and everything should be flowing 100%.