climate control diagnostic codes

[whitcre]

recently bought a 94 q45a with 55000 miles. i need the diagnostic codes for the climate control system( ac is blowing hot air but have plenty of freon). what kind of things do i generally need to look out for?

[Q45tech]

The absolute worst thing that can happen on a 94-96Q [assuming all the AC components are good and working] is for the plastic pin hinge on the air mix door to break and let the door stay closed in the hot position........the entire dash has to be dissassembled [10-12 hours labor minimum].

The codes are listed and the tests proceedures are delinated in the Service Manual. Hope it's something simple like a failed HVAC controller.

[whitcre]

it appears that it is code "25". the 2 is showing and the 5 is blinking. where can i get a service manual

[Q45tech]

25 is the sunload sensor open [if it had a minus sign in front it would be shorted].

Not usually a problem with heat????? but a real tech will need to decide about the mix door as the diagnostic can't check if the door is broken!

[whitcre]

not having a problem with heat, just air. what is sunload sensor and where isit located

[Q45tech]

You said your ac was blowing hot, I would say that's a problem with heat. Or do you mean that the ac is not cooling the air sufficiently below ambient. What is the inlet and outlet temperature in degrees.How do you know the weight of the R134a [freon]? Do you mean that a technican has measure the high and low [suction] pressures and they are ok per the service manual and the evaporator is cooling [feel the expansion tank] and the cool air is not being allowed in the HVAC system mix chamber?

Testing is required to differentiate between a mechanical failure [air door not moving] and a system failure [ac really not working].

[Q45tech]

All 90-96Q came with a mini [reduced print size] full service factory manual [and a small almost worthless owners manual]..........almost a thousand of pages of detailed diagnostic tests.

Just because the 25 shows a sunload sensor problem the top dash mounted passenger side unit cannot cause the full problem you describe.........it is to make minor corrections as clouds pass or you go into a tunnel.

[Ex-CA Driver]

OK Dennis, I saw what you said about his sunload sensor, but what does it mean when it flashes between 25 and a -26?

[Q45tech]

-26 means PBR is shorted refers to air mix door [told you to look there shop manual has hundreds of pages describing testing].....sensor tells the controller the position of door.......the door is commanded to go to open, anywhere in between, and closed......the sensor reports where it actually is! Shorted symbol may actually mean the door is not exactly where the controller commanded it to be stuck/broken/slippped.

HVAC diagnosis is a job for dealers as the system is difficult to get at and many oppurtunities to disconnect [make intermittent]other vital systems when you have dash apart!

When we have problems we first substitute a know good controller before ripping into dash!

If it was a Lexus I would say to look for Rats living inside HVAC, on a Q they live under the engine plenum [9 cases so far this year]...........never keep dog/cat food in Garage!

They use the plastic as a tooth brush/dental floss.

[whitcre]

i think the code is 55. on the diagnostics the "2" is constant and the 5 blinks twice