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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1672
Experience:  GM Grand Master Technician 2007. 14 year experience.
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2015 Gmc replaced compressor and expansion valve charged

Customer Question

2015 Gmc replaced compressor and expansion valve charged system gauges don't change and trucks not cooling. Ambient temp sensor showing -40. Will this cause the a/c not to work? I have taken the ambient sensor from my truck and put on my work truck no change reads the same. Sensor is not bad.
Submitted: 8 months ago.
Category: GMC
Expert:  david craig replied 8 months ago.

Hi Im David, you said the ambient temp sensor is reading -40 on your truck and -40 on your work truck?

Customer: replied 8 months ago.
the bypass valve is commanded 100%
Expert:  david craig replied 8 months ago.

if its reading -40 on both vehicles its bad. and it will absolutely affect the ac operation

Expert:  david craig replied 8 months ago.

is your truck auto climate control or manual?

Customer: replied 8 months ago.
auto. I figured it had to be with the hvac control module or the ecm I was sure what way to turn. These have a swash plate in the compressor and that's is way this is happening due to bad signals? So what need to be to fix this. I took the sensor from my truck and put it on this truck and nothing changes but my truck reads good this one is still bad.
Expert:  david craig replied 8 months ago.

i must have misunderstood, then the sensor reads good on one truck and -40 on the other?

Customer: replied 8 months ago.
My truck reads 97 with both sensors. The other reads -40 when you plug both sensors
Customer: replied 8 months ago.
Both sensors on one truck says 97 on the other both read -40
Expert:  david craig replied 8 months ago.

gotcha...man i confused myself right there........ok let me get a print for the system

Expert:  david craig replied 8 months ago.

The outside temperature will begin to update if driven above 20 mph (32 km/h) for at least five minutes. If the vehicle speed drops below 20 mph, the timer will reset and the display will stop updating. Once the display starts to update, it may take several more minutes of driving above 20 mph for the display to fully update.

Further, if the vehicle sits for at least eight hours, the display will be updated when the ignition is turned on

Expert:  david craig replied 8 months ago.

the initial problem may have been induced by disconnecting the battery

Customer: replied 8 months ago.
Ok I will try that when I get home and get back with you.
Expert:  david craig replied 8 months ago.

ok

Expert:  david craig replied 8 months ago.

any update?

Customer: replied 8 months ago.
The sensor is now reading correct but the bypass valve is still commanded 100% open. Any ideas?
Expert:  david craig replied 8 months ago.

ok. good. let me look into that. you are talking about the heater bypass valve correct?

Customer: replied 8 months ago.
The bypass valve on the compressor some people call it the swash valve
Expert:  david craig replied 8 months ago.

oh ok.

Expert:  david craig replied 8 months ago.

are you talking about the blow out valve?

Expert:  david craig replied 8 months ago.

im going to opt out and let another tech familiar with the inners of a compressor take over......good luck, glad the temp display works now though

Expert:  david craig replied 8 months ago.

never dealt with that valve or had any problem that that valve came into play.

Customer: replied 8 months ago.
I found the problem bad pin for the valve at the Eco connector thanks for your time I will go ahead and pay.