Air Conditioning problem
1998 Honda Accord 6 cyl Two Wheel Drive Automatic 265K miles
Hi. My a/c " cool" is operating erratic. Often, at engine start and when driving in hot weather with system in " auto", the cold air won't come out and the fan compensates at full fan. Warm, outside temp air, comes out. Then, suddenly, it will come on and stay on, and very cold, like normal. Sometimes the system powers up normally. Also, sometimes when I accellerate really fast, after a few seconds the air will start getting cold, sometimes very slowly and sometimes almost immediately cold. I know the condensor fan works, and I don't hear any belt squeels to indicate a loose belt. My Haynes manual describes how to get diagnostic information out of the display but when I follow the procedure it turns off the system off instead of giving me " 88" on the display. Any help here will also be appreciated. Thanks!
I have sent the diagnostic files to you, let me know if it is the same as described in your Haynes manual.
June, 29, 2010 AT 3:30 PM
Does it also do this in manual mode? Hondas use an expansion block system instead of a fixed orifice, the expansion blocks work very well, but do tend to stick sometimes which will cause warm air to blow instead of cold.
June, 29, 2010 AT 5:57 PM
I'll check to see if in Manual mode it does this, but I'm pretty sure it does.
The problem seems to be fairly predictable. The A/C will not cool unless the car is initially driven for about 3 - 5 minutes, then it comes on strong. Almost sounds like a relay or some sensor acting erratic. Yesterday I checked the freon pressure and it was at the low end, 25, during idle, and when the clutch engaged it would go up past 30. So I added some freon. What I'm not sure of is if the clutch is engaging when the car is first driven.
June, 29, 2010 AT 9:55 PM
It should be around 30+ psi when idling hot and the clutch engaged. Try holding therpms up around 3k to see if thecomp stays engaged, this will at least tell if it is working at higher rpms like when driving it. What you describe could be a low charge or the expansion block
June, 29, 2010 AT 10:07 PM
It makes no difference if I take the system out of auto mode and into semi-auto. What I did notice today is the clutch is not engaging at cold start, even when the radiator fan is engaged (when A/C on). I actually took a flash light and observed the clutch under the hood. But after a short drive, the system starts working. I checked under the hood and noticed the clutch engaging and disengaging along with the radiator fan after that short drive.
Now, however, after recharging the system, I have a new problem! After the system warms up, it cycles on only momentarily, then off as if it were in some sort of self protection mode. The cooling is degraded, as you might expect. This just happened last night after I finished recharging the system. I left the car sit for about an hour, then I put the pressure gauge on it and while the compressor was engaged continuously (before it went into the cycling mode) it measured 32 PSI. But when I took a static pressure reading after engine shutdown it built up from 50 PSI all the way up to 80 psi. I'm not sure what the static pressure should be, but perhaps I've overcharged causing this new system power on/off cycling problem? When it cylces on/off you can hear sort of a metallic " pop".
June, 29, 2010 AT 10:10 PM
Thats bad, there is too much in the system and it is shutting down due to excessive high side pressure. When the engine is hot and idling it should be around 30-35 psi with the comp engaged. DO NOT run it anymore with out having some of the 134a evacuated or it could damage the comp
June, 29, 2010 AT 11:44 PM
Thanks. For the original problem, do you still think the expansion valve might be the problem after describing my original symptoms? Or could it be the air conditioning pressure switch located on top of the receiver-drier?
Any easy way to let some pressure out of the low pressure end other than taking it in for servicing? I just so happen to have one of those r-134 bottle screw on trigger valves that I can no longer screw on to another bottle because it would not spin off the old r134 can. But the trigger valve still works fine, and the hose attaches to the low end of the a/c system just fine as well. I know if I attach it and press the valve it would release pressure, I just don't know if that is considered ok to do. Or, if the a/c low pressure attachment point is like a schraeder valve, can one just push it to release pressure (again, low end side)?
June, 30, 2010 AT 7:43 AM
I cant condone releasing refrigerant into the air. It is supposed to be reclaimed by a recovery machine. What you do that I dont know about might just work though. It may be the cycling switch, but the pressures need to be correct first. Then hold higher rpms to see if clutch stays engaged. To really see what is going on, it may be necessary to have a full gauge set (high and low sides) on the system to see what is happening. This will also show if the expansion block is indeed sticking or not responding correctly
June, 30, 2010 AT 9:54 AM
Thanks. I very much appreciate the advice. I know the compressor is working at high rpm AFTER the initial 3 to 5 minutes of driving because once the a/c engages at that point, it works like normal for hours. And even if I turn off the car for 15 mins, it will start up with the a/c working. But the longer I let the car sit (more than 30 mins), the more probable I will not have a/c when I initially drive the car, but until 3 to 5 mins later (and in my neighborhood in the summer, you can boil in that time!).
Perhaps another clue is, when the a/c decides to turn on, it doesn't always turn on " full cold" it often gradually builds up to full cold over the course of 2 mins or so. So, we have two symptoms: 1) no compressor engagement first 3 - 5 mins of driving; 2) when a/c finally starts working, it often gradually builds up to full cold.
July, 1, 2010 AT 8:15 AM
Since it does this in both modes, Im still thinking something mechanical like the expansion block, but until the pressures are checked on both sides in all conditions it is hard to say.