AC Controls

[mike561]

my 98 gp has the digital dual climate thermostat for the AC controls (not the one with the dials, but the buttions and the display instead) and its reading the temp in celsius, i wanted to know how to get it back to reading fahrenheit, i had the AC repaired and after i got it fixed it went into celsius mode, i dont know what they did to it, could someone maybe check their service manual or something and see if theres a way to set this back to fahrenheit? thanks!

[troy1]

I looked could not find anything sorry

[mike561]

k, thank you for looking anyways

[BNaylor]

I'm assuming since you have the digital dual climate HVAC controls you have the Driver Information Center (DIC). On most GM cars that have DIC you set whether you want the readout in English or Metric (E/M) at the DIC.





Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[mike561]

i think i might have DIC, how would i know? and where would it be

[BNaylor]

Originally Posted by mike561

i think i might have DIC, how would i know? and where would it be

It should be located to the right of the steering wheel in the center of the dash above the center AC vents and center console. It has 3 buttons and a digital display. The buttons are marked ENG/MET, RESET and MODE.

If you have a DIC the button you press is the ENG/MET and it will change the temperature to farenheit.





Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[mike561]

oh ok yea i got DIC but it diddnt change it back to fahrenheight, i held it down for a few seconds, and nothing, would there be any online instruction manual about the thermostat ac control?

[mike561]

if i took out the ac control deck from the dash, would anyone know if there might be a switch somewhere on it to change the temp readout?

[mike561]

sorry if i seem like such a pain in the a** about this, but its been irritating me so much. if anyone has any suggestions or site links about this please let me know. thank you!!!

[richtazz]

I have the same control in my 99, and the DIC is not connected to the A/C controls. I checked my owners manual, and it doesn't say how to change from C to F, so i tried every button combo I could think of and it wouldn't change. Are you sure they didn't replace your unit with one calibrated in Celcius by mistake?

[mike561]

yea im pretty sure, i dont think my mechanic would have one just sittin around his shop, ill have to ask him about it. it was in fahrenheight when i bought the car. if i have to then i may just end up getting another one from ebay or something, hoping that one is in fahrenheight.

[richtazz]

I'll keep digging for you, and see if it's changeable. I'll let you know how to do it if I find it.

[BNaylor]

I didn't know GM had two different digital AC head units for the Grand Prix. Ive only seen one GM part number. What makes it switch between English or Metric is a simple ground which originates at the passenger side fuse block area. The Grand Prix's AC/Heater control relative to setting the display in fahrenheit or celsius is not as sophisticated as other its GM counterparts.

Anyways, here's his problem. There are 2 main connectors at the back of the HVAC control unit. C and D. At connector D there is pin D7. This is the English/Metric connection point. If this point is grounded it reads Metric-Celsius. If this is open (no ground) it reads English-fahrenheit. The ground originates from ground number G201. BTW - The specific wire you will be looking for is black.

Based on Richtazzes theory that you got a head unit wired in Celsius, then someone screwed up by putting a ground in the AC/Heater control panel and not in the wiring from the connector plug and back but its a possibility.

If you're handy with a multimeter, set it to ohms - resistance. Check at connector D, pin D7 relative to ground. If it reads a short then its set for Metric. All you'll need to do is open the wire at this point to read fahrenheit. And if I have time I can send you the 97 - 98 GP wiring diagram but I don't know your competency level in DIY and electrical problems. Good luck!





Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[WRBsGTP]

Before you start re-wiring your unit, you might want to try holding the driver and passenger buttons down at the same time while the fans are off...The readout on your screen should change to "00" and then your driver-side dial should allow you to switch from farenheit to celsius.

[mike561]

Originally Posted by WRBsGTP

Before you start re-wiring your unit, you might want to try holding the driver and passenger buttons down at the same time while the fans are off...The readout on your screen should change to "00" and then your driver-side dial should allow you to switch from farenheit to celsius.

ive tried that and it DID readout the "00" but when i turned the dial the numbers would just change from numbers 00 through 22 and if i moved the passenger dial it would change to just a random number, like 173 or 11 and still stay in celsius. Is there another way to do that maybe? if not then ill take out the ac head unit and check the ground points, that sounds like it may be the problem, if you do have an electrical readout that you can send that would be helpful. ill let everyone know how it goes. thanks again everyone for all this help!!