A/C resetting

[dwhisent]

92 PA, 111K miles

I just did a bunch of work trying to get the A/C going on my PA, including replacing the evaporator, accumulator, compressor, etc., and I'm almost there (many thanks to HotZ28 for all his help and advice). The A/C works great now, except for one thing - the system keeps kicking out.

I can reset the PCM by unhooking the neg cable from the battery and waiting a while, then reconnecting, and the system will work fine for a while - perhaps a couple of weeks, maybe only a day. Then it kicks out (the "auto" button on the climate control will not come on), and the compressor will not kick in until I reset things again.

What might be some things to look for? I do have an SES light showing, and the mechanic said it indicated the cam or crank sensor, and I will investigate these as I have the chance, I have seen some threads on these, but I would not have thought that would affect the A/C system.

Of course this is not really high priority right now, with cool weather approaching. But I would like to get it fixed before next summer. If all else fails, I could pull out the A/C relay, run some wires from the A/C relay base to a switch inside the car, and work the A/C manually, but I would rather fix it right.

Thanks.

[HotZ28]

Hello Doug, good to here you got the PA back together. One thing I wanted to mention before I list the procedure for resetting your ECC. The ECC controller has many functions, in addition to controlling the AC system! It also serves as a code reader for the AC system and the PCM. You can monitor sensor functions and even display vehicle speed on the ECC display! I will not get into all the details of that in this post, however if interested, let me know.

When the ACC control unit starts flashing, it is storing a fault code. You may be a little low on Freon, or you could have other problems. Use the procedure below to see if you can retrieve the codes. After resetting the codes, the compressor should cycle on. If not, try disconnecting the battery negative cable for 30 sec. That will clear any memory from the ACC & PCM.

This procedure will work on 1992 -1993 models with ATC, and may also work on 1988-1991 models. 1994 up, you need a scanner with this capibility.

The diagnostic mode also contains a data list mode and an override mode.

Be careful not to select modes 01 or 02, as these are different modes and may cause you problems, if you don’t know the functions of these modes.

If you suspect you are in the wrong mode, press OFF repeatedly until you exit to normal mode. If the temperature display flashes for 2 minutes when the ignition is turned to RUN, a trouble code is set.

1. Turn ignition to RUN. Press OFF and WARM (temperature up) buttons simultaneously.

2. Watch the segment test, then the trouble codes will be displayed.

3. Code Key:

00 - No codes

10 or 110 - Ambient Temp Sensor circuit open or shorted.

13 or 113 - In-Vehicle Temp Sensor circuit open or shorted.

15 or 115 - LH Solar Sensor circuit open or shorted.

35 or 135 - Data Line failure - HVAC Control Assembly

38 or 138 - Data Line failure - PCM

40 or 140 - Driver Air Mix Motor circuit open or shorted, or not calibrated

48 or 148 - Long Term Freon Loss

52 or 152 - Keep Alive Memory lost; sets with battery disconnected

66 or 166 - Low Freon

A number (1) prefix, indicates a history trouble code.

4. Press OFF twice, once codes are displayed to end diagnostic mode, OR to clear trouble codes, press FAN DOWN three times (make sure 03 is displayed).

Once 03 is displayed, press FAN UP to clear trouble codes. Then repeatedly press OFF to end diagnostic mode.

Almost forgot to mention, you are right, the crank or cam sensor has nothing to do with the AC functions.

[dwhisent]

Wow, thanks! I would have never suspected that existed. I'll give it a shot, as soon as I can get the Buick back from my son again.

I have seen the temp flashing, but I never knew the reason.

[dwhisent]

OK, gave the diagnostics a shot. It gave a 166 at first, after resetting gave a 66, which from above indicates low freon. A bit tough to believe, since it began behaving like this immediately after the mechanic charged it and leak tested it, and after resetting (by disconnecting the battery) it cools great.

So maybe a bad pressure switch somewhere? Unfortuntely, I don't have a gauge set to test it with, but I might spring for one from harbor freight, only about $20.

Again, with winter approaching I have lots of time to figure this one out. I'll move on to questions about more critical issues using another post.

Thanks for the help!