TDK Posted May 10, 2004 Report Share Posted May 10, 2004 Got to get the "Big Red Dog" ready for some sprinting around the desert again... The AC works great if set to 60F (the lowest) but not very well at any setpoint above. This "problem" (or maybe it just how it is...) has been around for a few years perhaps. I recalled that someone mentioned that the lowest setpoint will cause the AC system to not recirculate or something. Observations & Relavant History 1. I think that the compressor, belts, etc may have all been changed just before I got it. Was my company car and my boss wanted to have it nice for me. 2. Have not had any codes for the last 102,000 miles, when I bought it (186,000 total now). For that matter, I cannot ever recall any codes ever! 3. The AC compressor always seems a bit noisy when ON, but belts, supports, etc all seem OK. 4. The refrigerant was checked early last year (no problem ?). 5. I checked the refrigerant low and high side pressures last fall and they seemed OK. Question A: Is there a problem to operate AC at the 60F mode for hours on end (if not recirculated or whatever)? I adjust the fan speed to compensate for lack of temperature modulation, but its getting old after a few years... Question B: I was hoping there was some way to adjust the in-cab thermostat to make the AC kick in, yet modulate at a slightly higher temperature. Question C: Is there any way to have the DIC display the in-cab temperature? Question D: Could the aspirator or sample pump for the in-cab temperature sensor be a problem? Tried to seach for this in achives, but not much luck. Thanks in advance for any help Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
KevinW Posted May 11, 2004 Report Share Posted May 11, 2004 60 F is an override setting for maximum cooling; high fan speed is commanded, along with the air-mix door at the full cold position and an open recirculate door. Running hours on end with 80-90% recirculated air while the compressor is running may cause you to blink more frequently. The in-car temperature sensor doesn't regulate compressor activity; the compressor is requested to run above a certain ambient temperature and if a setting other than OFF or ECON is selected. In diagnostic mode, monitor ACP Data AD25 for an in-car temperature sensor reading in degrees Celcius. Also, check AD22 (commanded mix door position) and AD23 (actual mix door position). ___________________________________________________ Link to comment Share on other sites More sharing options...
TDK Posted May 13, 2004 Author Report Share Posted May 13, 2004 Kevin, Thanks for the advice. And I thought the compressor turned on/off via the thermostat! I should have realized a Caddy would have a much more sophisticated method to hold the AC setpoint temperature... In trying to comprehend your expanation about what regulates the AC compressor: I have postulated that the compressor modulates primarily per suction pressure, as generated by heatload, which in turn - was generated by the cabin air movement via the air door - as it regulates the cabin temperature. OK? ACP data #25 (actual cabin temp) = 20C. This seems reasonable since the AC setpoint was 18C (65F) and the cooliongs air doors were moving (to icrease cooling I would hope). The air door commanded position and actual position were changing as I opened windows etc, but remained within 1 unit (degrees out of 90?) to each other. This seems normal, if increasing values also denote increasing cooling capacity. Still no current codes in any system. I suppose I should be thankfull and look for something else to explain the apparent lack of AC cooling. Quite a few years ago I recall finding an article of clothing that had somehow become jammed into a vent under the dash, causing a heating problem (in the car). I am almost scared to look for the same sort of thing now... Well, I did find and clear some history codes for the suspension: S021/S026 (Left and Right Rear Dampner shorted to ground, S044 (Lift or Dive signal failure), and S055 (Resistor module short to ground). What's a Dampner in these terms - the rear struts? I'll see if these codes reappear. They may have occurred during some interesting "ground-effects" on a back-country dirt road. <_< I have a list of fault codes, but where are the multitude of data codes listed? BTW, Thanks again Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
KevinW Posted May 14, 2004 Report Share Posted May 14, 2004 In trying to comprehend your expanation about what regulates the AC compressor: I have postulated that the compressor modulates primarily per suction pressure, as generated by heatload, which in turn - was generated by the cabin air movement via the air door - as it regulates the cabin temperature. The ACP cycles the compressor in response to (primarily) evaporator inlet temperature. The pressure drop across the evaporator, system load, compressor RPM, etc. would determine how closely this is related to the suction pressure. Actually, the air mix door position does not change the heat-load. All incoming air (outside or inside mixed with 10-20% outside) passes through the evaporator for dehumidification prior to reaching the mix door; it is then heated as necessary to maintain/approach the interior temperature setting. The load on the system is dependent mainly on incoming air temperature, humidity, and volume. If the interior temperature is indeed 20 C (68 F), I would expect the system is mixing in some heat since the set temperature is roughly 3 F lower and the system would be approaching an equilibrium. There is an "offset" that can be used to tune the setting +/- 5 degrees if necessary; this is available under IPC override IS10. ___________________________________________________ Link to comment Share on other sites More sharing options...
rek Posted May 14, 2004 Report Share Posted May 14, 2004 KevinW, How about an IPC overide tutorial for "Dummies". TIA rek Link to comment Share on other sites More sharing options...
careldo Posted May 14, 2004 Report Share Posted May 14, 2004 Yea i'll second that Link to comment Share on other sites More sharing options...
TDK Posted May 15, 2004 Author Report Share Posted May 15, 2004 Kevin, AHA ! I think the AC thermostat "offset" what I was trying to describe all along. I do not want the max setpoint of 60F and I know the system is not cooling to its capability or given setpoint. I had already "hand-temped" the AC cannister at idle - YOW ! it was for sure working OK and confirms the AC refrigerant pressures are still OK. I found IPC Override IS10, but it does not seem to have any data displayed notr does it have a "data input area". IS08 and IS09 have data nd underscores for input it appears. I didn not attempt change them, since I have no clue as to what they are. However, I'm not too sure how to change IPC override anyway. By the recent posts, you seem to be the AC Guy. What's with that and being up in Canada ? Thanks again, again. Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
Ranger Posted May 15, 2004 Report Share Posted May 15, 2004 KevinW, How about an IPC overide tutorial for "Dummies". TIA tutorial: http://caddysearch.netgetgoing.com/mbarchi...?id=IMPORT-5928 Link to comment Share on other sites More sharing options...
TDK Posted May 15, 2004 Author Report Share Posted May 15, 2004 Kevin & Larry, You be 'Da Men ! After Larry's link to the tutorial, I opened my eyes and happened to notice the temperature setpoint to the right, in its regular window - was waiting for input, duh. I set IPC IS10 override for -5. The temp setpoint happened to be 65F and immediately after after I changed IS10 - I heard the blower increase (or more air to the top vents) and an air door move. It seemed cooler and given the actions noted above, I think the -5 override means a setpoint display of 70F will now try to hold 65F per the cabin sensor. Gentlemen - thanks again, again and again. Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
KevinW Posted May 15, 2004 Report Share Posted May 15, 2004 rek, the procedure is a bit different for 1996. According to the service manual, the Set Temperature Offset for 1996 is on IPC override IPS06. Once in diagnostic mode, answer the prompts using the fan HI (yes) and LO (no) buttons until you get to the IPC Overrides section. Once at IPS06, use the WARMER/COOLER (or Passenger side controls for the analogue IPC) to change the value displayed on the trip odometer. To store changes, press and hold FRONT DEFROST and AUTO/ECON or FRONT DEFROST and A/C for analogue clusters until the trip odometer flashes once (approximately 5 seconds). TDK, you'd be surprised how hot and humid it can get here! Maintaining my A/C became a hobby after I couldn't find anyone that would do a thorough job. ___________________________________________________ Link to comment Share on other sites More sharing options...
KHE Posted May 15, 2004 Report Share Posted May 15, 2004 Maintaining my A/C became a hobby after I couldn't find anyone that would do a thorough job. That's exactly how I started doing my own A/C work. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
rek Posted May 15, 2004 Report Share Posted May 15, 2004 Thanks Guys for the info. I do my A/C work as a "Hobby" too, if you want to call it that, and for the same reasons- to fix it right. Hey, it's Sport or fun to DIY, especially if it comes out working right... rek Link to comment Share on other sites More sharing options...
Ranger Posted May 15, 2004 Report Share Posted May 15, 2004 Can someone explain the reason for the override? If 70 is too warm, why not just change the setting to 65? Why did GM even bother programing that override? I must be missing something. Link to comment Share on other sites More sharing options...
rek Posted May 16, 2004 Report Share Posted May 16, 2004 IF the sensor/aspirator is good, and the set Temp and cabin temp aren't the same, and the commanded position and actual position are in sync, then it's override time. If you set it for 70 and what you get is warmer than 70 (Hand held instant-read thermometer) you gotta do something... If it's not crud blocking the air-flow, or a dirty cabin filter,(for those that have them). rek Link to comment Share on other sites More sharing options...
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