2011 Quest No AC

[langer5192]

Hello,

I have a 2011 Quest and AC is not working. Shop tested freon levels, all sensors and fuses and no issues there. When compressor Jumped with 12v it turns on and blows cold air. The IPDM (fuse box with integrated ac relay) was tested and is working as intended as a force test (door switch test) was engaging the Magnetic clutch on ac compressor. The Shop told me when hooked up to a computer, the Car would not indicate any ac request when ac button in cabin was engaged. Was told I have to take to a Stealership. I am now thinking it is the Body control module but not sure. Any tips or help would be appreciated! Thanks!

[VStar650CL]

There are four devices involved in turning on the compressor in any late model Nissan. The chain goes from the HVAC controller (A/C Auto Amp) to the BCM, ECM, and IPDM in that order. The BCM's only task is to make sure the blower is running and (on some models) not jammed, so it's pretty unlikely that's your issue. If the ECM isn't seeing any request, it's more likely you have a bad sensor. On a Manual system you have the Ambient sensor (in the grille) and an Intake sensor (on the evaporator). On an Auto system you have two additional Cabin sensors, one front and one rear. If any of those are open-circuit they will read "Siberia" and the HVAC will refuse to request the compressor. The Ambient is easy to check, it's the temperature reading on the dash. The others can all be checked by taking the sensor connector loose and shorting the two wires. That turns the reading from Siberia to Sahara, so if the compressor starts, you've found the culprit. Unfortunately the '11 FSM here in Nico is missing the HAC section, but I'm pretty sure the guts are similar or identical to a '14. So you can find the sensor locations here starting on HAC-8:
https://www.nicoclub.com/service-manual ... %2Fhac.pdf

[langer5192]

the guy at the shop said he checked all the sensors but ill take look. i know the ambient temp sensor is good but will check out the evaporator sensor next. i have manual ac not auto so those should be it other than pressure sensor

Thank you!

[VStar650CL]

the guy at the shop said he checked all the sensors but ill take look. i know the ambient temp sensor is good but will check out the evaporator sensor next. i have manual ac not auto so those should be it other than pressure sensor

Thank you!

You're most welcome. He could check the pressure sensor with a scan, the ECM monitors that and any scanner can pull it up. It's very doubtful he has a scanner which can pull up the evap sensor, that's monitored by the HVAC. One other thing when you check the sensor. It's a regular 2-wire RTD, so a voltmeter can tell you everything you need to know. You should see 5V on the data wire with the sensor disconnected, if you see 0V then there's a broken data wire or the control head is bad. If that checks out, short the wires and check again. You should see 0V, if it's still 5V then the ground wire is broken.

[langer5192]

Okay so i found my Evap sensor, im not too knowledgeable with electrical stuff so my buddy went and checked it out. we forgot to check for the 0v and 5v but He tested the evap temp sensor and it is reading 0.0 ohms resistance. Would that indicate a broken sensor? by the look of the graph in service manual that reading would not be posssible. Maybe abnormal reading is telling computer not to request ac?

[VStar650CL]

That's basically a short circuit, so it should be telling the HVAC that the evap is super hot. None of the HVAC's I've ever seen error-check the sensors, but I won't say that's impossible. Calsonic doesn't give us flowcharts, and the Quest has always been a redheaded stepchild with oddball hardware. You can check it by sticking a 2.2K resistor in place of the sensor and see if the voltage on the data wire matches the chart. If it does and the compressor is off because of a software safety, the compressor should start. If the voltage doesn't match then you have a wiring problem in addition to a shorted sensor.

[langer5192]

Would this work ? Thank you

[VStar650CL]

Yep. The circuit carries very little current, even a tiny 1/8 watt will do fine.