Automotive Air Conditioning Information Forum (Archives)

somedude01 on Thu July 28, 2011 9:49 PM

Year: 1990
Make: Honda
Model: Civic Si
Engine Size: 1.6L
Refrigerant Type: R-134a
Ambient Temp: 95f
Pressure Low: 33-50
Pressure High: 220-240
Country of Origin: United States

Hi everyone, long time lurker, first time poster. I have a few issues that I probably already know the answer to, but needed reassurance before I rip my system back apart.

I have built the system as follows:
New:
TXV
Matsushita Compressor
Parallel flow condenser 12x24 from AMA (thanks!)
Evaporator (Also AMA)
O-ring kit (O-rings and fittings coated with Nylog Red)
R-134a dual pressure switch
R-134a Thermostat
Discharge line (Other one exploded 1 car ago)
5oz of BVA auto 100 Ester, as per the manual for a Matsushita system

I reused all of the hardlines, which were flushed with Brakekleen and thoroughly dried with shop air with an inline drier for several minutes each.
A custom seal between the condenser and radiator was made with Coroplast, Honda designed this car with a rediculous gap between the heat exchangers, so I forced the entire radiator to breathe through the smaller condenser.
I evacuated the system to a rough 29inch vacuum, at least that's what my gauges said. I used a venturi pump, I have a 60 gallon 6.5hp air compressor, I hope it was enough. It only took about 5 seconds to pull it into the 29" vacuum.
It held a vacuum for a half hour with the pump off, and the system was evacuated for an hour total.
I charged the system with ROUGHLY 2 1/2 12oz cans of R-134a, original R-12 spec was 32oz. I'm too cheap for a shop or a charging station, I hope this move was alright.
Vent blower is on steroids, it moves ALOT of air. Condenser airflow is also adequate, both fans on the condenser are working great and appear to pull alot of air. Airflow is going into the engine bay, that was double checked.

Now the problem: Inadequate cooling... Typical of this year Honda with a retrofit, I read.
The system cools to 65f vent temp, sitting at about 750 rpm idle, max fan, recirc and everything closed up. Idle pressures are roughly 40-45 and 220. When revved up around 1500 rpm, it pulls the lowside down to a nice 33 psi and highside goes to roughly 240, yet only slightly better cooling at about 60f vents. Fan in front of the bumper does nothing, misting the condenser drops the high side to 180 instantly, no change in temps(I assume my custom seal is doing good). Humidity was around 55% during both of the tests, ambient read 95f and temperature at the bumper read 100f. Tests were done in the shade and the car closed up. If I did it with doors open, it barely even cooled if it can be felt. It eventually gets ice cold the longer you drive it, but the vent temperature just doesn't get cold until you drive it long enough or it rains, or it's early morning or at night..It's barely enough to keep you from sweating. The car also has tinted side windows, if that makes any difference.

So this brings me to my original question.. Will a reversed Reciever drier cause these symptoms? I noticed when making the custom lines, that we plumbed the receiver drier backwards, with the in arrow going out toward the Evaporator inlet...I haven't found a definitive answer to this question, but, I did a flute test on the old one and the outlet makes a deeper tone. I assume it draws liquid from the bottom when properly hooked up.
The sightglass has alot of large bubbles in it, and they have a swirling motion instead of a flowing motion, almost like flushing a toilet. The bubbles disappear completely and the liquid appears to recede in the bottom when I misted the condenser in the prior test.
I'm hoping my issues are that the TXV isn't receiving any liquid refrigerant to meter because I mounted the receiver drier backwards, and not because this system just sucks...

I apologize for the long read, but I am trying to supply enough information to be helpful.

I appreciate any light on the matter, criticism is fine.

Edited: Thu July 28, 2011 at 9:52 PM by somedude01

TRB on Thu July 28, 2011 11:52 PM

You need to get the correct flow on the drier before we can address anything. It matters.

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somedude01 on Sun July 31, 2011 1:35 PM

I've got an update to my original post, and it's almost the same as before. I took the refrigerant to be reclaimed and brought it home and swapped the lines around, I pulled another vacuum for an hour and recharged.

I charged the system with R-134a until the sightglass cleared this time, I did not see any foam or milky texture, just crystal clear fluid and a little hue of neon green dye..

Pressures and temps are as follows:

Readings were recorded in half shade, half sun as I was under a tree til it rained. Windows were open, doors closed. Recirc, fan on max, no misted condenser or box fan in front of car.
Ambient 95
Temp F at bumper 100f
Vent temp 60? (at this point I am doubting my thermometer, it's old.)
Low side: 40-50
High side: solid 240-250

I was not able to mist the condenser this time around as I got rained out, Florida is notorious for that. And I wasn't able to do a 1500 rpm test for the same reason. Those readings were at idle. The car does cool down as long as you're driving along at 40mph and around 2k rpm, but warms slightly at stoplights.

What I was able to note, however, is that the suction line was ice cold and hurt your hand to touch. Sweaty, but not frozen. Is it possible i'm dealing with a heater valve problem now? And my gauges were not calibrated, so those readings may be skewed.. My low side seems a touch too high, as well. When I was charging, after the second can emptied, I noticed the pressures did not change at all from the end of the second can and all through the 3rd until the sightglass cleared. Turning the blower down to 2 eventually makes the lowside drop below 30, and makes the compressor cycle.

bohica2xo on Sun July 31, 2011 3:10 PM

Make sure the condensor is coupled to the radiator & fan assembly. No air should be able to bypass the condensor on the way to the radiator. If there is a gap between the radiator & condensor, it may be necessary to seal the gap around the edge of the condensor. Usually some foam weatherstrip from the hardware store will get the job done.

Your pressures don't look bad, but you may have some reheating of the air in the cabin. Blend doors / water valves are the two main causes of this.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

somedude01 on Sun July 31, 2011 3:47 PM

There was a rediculous gap between the heat exchangers when I first assembled it. I went to lowe's and bought a yard sign made of coroplast and sealed the edges between the larger radiator to the smaller condenser, there is no airflow bypassing the condenser. I also used the weatherstrip sticky foam to seal the fans to the radiator, as there was a 1/4" gap between the shrouds and radiator. I'll tackle adjusting the heater valve tomorrow and see where that gets me, it likely hasn't been adjusted at all in the 21 years this car's been around. If all else fails, I might wind up using R-12. This is no fun in Florida the way it is. :/

One more question, if misting the condenser drops temps as well as pressures, should I look into new fans? These appear to move alot of air, but one fan is the original radiator fan, and the other is an ebay special.

bohica2xo on Sun July 31, 2011 4:00 PM

The improved cooling at road speed is usually a sign of inadequate condensor airflow from the fan(s) or a coupling problem. Since this is a custom system it is a little harder to point the finger at a single issue. Sounds like you have the heat exchangers well coupled. That leaves the fans.

The heat load where you are is extreme. The water valve is a good place to start. Sounds like you are getting closer to good cooling.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

somedude01 on Sun July 31, 2011 4:12 PM

Thank you for your suggestions and help. I'm going to buy a new meat thermometer tonight and use them side by side in the vent to check for error. Tomorrow i'll adjust the heater valve and do a 1500rpm test, as well as use a box fan in front of the car to see what difference it may make, and i'll mist the condenser if the fan doesn't seem to change anything. I'll post back with results, hopefully good!

somedude01 on Sun July 31, 2011 9:51 PM

It is not a heater valve issue. I drove the car home tonight with the a/c off, and the dial set to full cold with no blower on, and with the way this car is designed you can take the center vents off without tools and reach your hand and touch the heater core. I touched it and it felt like it was ambient temperature, and the blend door moved like it should and closed off the path to the heater core when set to full cold.. I'm at a loss now, should I just revert to R-12 if it fails the box fan and misting test?

somedude01 on Mon August 01, 2011 4:48 PM

I believe I have found my problem. I used a venturi pump, doing more research I read that it's not good enough to pull a real vacuum... Can anyone chime in with their experience using a venturi vs an electric pump, and if it made their a/c work any better when they used an electric one? Currently my a/c only works awesome in the rain, at night or in the morning.. The second you give it some heat load, it sucks... And my low side never being below 40, does that signal an air/moisture contamination issue?

mk378 on Mon August 01, 2011 5:40 PM

Air in a system is always bad, so don't use venturi pumps. Charge to the full specified R-12 weight (which I think is 32 oz) in R-134a and see what the pressures do. Generally, ignore the sight glass on R-134a systems. You may want to road test with gauges attached to eliminate rpm and airflow issues.

I have a converted '91 Civic DX, completely stock including serpentine condenser, it does about as well as what you have. I would not expect vents below 60 in 100F ambient. The air inlet control should be set on recirculate in any sort of hot humid weather. Scroll compressors also have poor performance at idle, it is their nature.