3rd - my 07 H3 always runs a tick above halfway if it is 80 or above out. The only time it is below halfway is in cool temps. Climbing long hills in AZ heat puts it close to 3/4 heat. I've only had the "AC OFF" message once, that was when trying to do 95 mph in 112 degree heat.
Hans, I think you need to start logging the issues. Also, read below. I don't think this exactly applies to you as your issues may go beyond calibration of the gauge if you're actually getting the AC OFF message
#PIP4443A: Engine Temperature Gauge Displays 3/4 In Hot Ambient Temperatures - (Jan 7, 2009)
Subject: Engine Temperature Gauge Displays 3/4 in Hot Ambient Temperatures
Models: 2008 Hummer H3
with 5.3L V8 Engine (RPO LH8)
--------------------------------------------------------------------------------
This PI was superseded to include repair information and internal faxable information for vehicles pre breakpoint. Please discard PIP4443.
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may be concerned that the engine temperature gauge reads just below the red (around 3/4), when driving in ambient temperatures of 100 F (38 C) or higher. This concern is typically more apparent when driving up steep grades for several miles, or in stop and go traffic for several minutes, with the air conditioning is on.
There will be no sign of coolant loss or underhood steam noted by the customer. Upon inspection, no DTCs or coolant loss will be noted, and the ECT sensor parameter on a Tech 2 will display less than 230 F (110 C) if the concern is verified by a technician.
This may be due an instrument panel cluster (IPC) calibration concern and excessive hot underhood air entering the engine air inlet.
Recommendation/Instructions:
If SI diagnosis does not isolate a cause for this concern, note the vehicle build date.
If the build date is 7/1/2008 or later, replace the IPC with part number 25946690, which includes updated calibrations to improve this concern. For export vehicles, use part number 25946691.
If the build date is 6/30/2008 or earlier, please contact U. S. GM Technical Assistance at 1-877-446-8227 or Canada TAC at 1-800-263-7740 English or 1-800-263-7960 French for additional information.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
For the I5 engine, see this
#PIP4464A: Engine Temperature Gauge Displays 3/4 In Hot Ambient Temperatures - (Dec 23, 2008)
Subject: Engine Temperature Gauge Displays 3/4 in Hot Ambient Temperatures
Models: 2008 Hummer H3
with 3.7L Engine (RPO LLR)
--------------------------------------------------------------------------------
This PI was superseded to include new repair information. Please discard PIP4464.
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may be concerned that the engine temperature gauge reads just below the red (around 3/4) when driving in ambient temperatures of 100 F (38 C) or higher. This concern is typically more apparent when driving up steep grades for several miles, or in stop and go traffic for several minutes, with the air conditioning turned on.
There will be no sign of coolant loss or underhood steam noted by the customer. Upon inspection, no DTCs or coolant loss will be noted, and the ECT sensor parameter on a Tech 2 will display less than 230 F (110 C) if the concern is verified by a technician.
This may be due to an instrument panel cluster (IPC) calibration concern.
Recommendation/Instructions:
If SI diagnosis does not isolate a cause for this concern, replace the IPC with part number 25946690, which includes updated calibrations to improve this concern. For export vehicles, use part number 25946691.
