sparky1562

Problem: When in Auto mode, set to heat (setting higher than outside ambient), discharge air is 5 to 10 degrees cooler than setting. When in Econ mode, discharge is equal to set point.

History: AC has not worked well for several years. Replaced AC compressor, dryer, expansion valve last month and works great in cooling mode. I ran the control panel diagnostics before touching the AC and no problems detected. Took the evap out, cleaned it, replaced expansion valve, put intake air sensor back on.

All control doors working, blower working fine, nothing appears wrong. Air temp was mid 60's, had the temp set for 73 in auto, gauge stuck in air outlet read 62-65 ish. Put in econ mode, went to 73.

What do I check first?

DennisMik

iTrader: (2)

The car has temperature sensors that are used by the auto climate control to determine that temperature of the air coming out of the ducts. There is a self diagnostic built into the controls that will check these. The diagnostics has 5 major sections and the sensors are tested in section 2.

The diagnostic is described in the FSM is section HA (Heating and Air Cond.). It starts on page 70 in my 97 manual, but other year's manuals could be different.

If you don't have the manual, you can down load one from here -

http://boredmder.com/FSMs/Nissan
-or-
http://boredmder.com/FSMs/Nissan

The file named fwd.pdf is the "cover page" file, the starting point.
The file named idx.pdf is the alphabetical index file.

sparky1562

I do have the FSM. I am guessing it is one of the temp sensors. Have not any time to mess with it yet. When I figure it out, I will post what I find.

njmaxseltd

iTrader: (19)

Discharge air isn't equal to set point. Discharge air will cool or heat to OBTAIN the set point in the cabin. If the cabin is 75 degrees, outside air can be 60, if you set the climate control to 72 - It's going to blow cool air to bring the 75 degree cabin down to 72. ECON does the same thing only without the compressor running. It simply will not cool lower then ambient temp (intake air temp at the cowl) but will heat as required.

I don't think you have anything to check, it's working correctly. ECON mode doesn't run the compressor. In AUTO mode your 62 - 65 air was coming in to maintain your set point of 73. Cabin temp must have been warmer then 73 and your sun load sensor was probably also calling for a little cooling.

Does the climate control maintain the cabin temp correctly? You set it to 70, does it heat or cool to obtain the correct temp? Don't pay attention to discharge air temp, it will vary according to various sensors to keep the cabin at the temperature you select.

sparky1562

On the day in question, with the set point around 75, outside air around 67 or so, in Auto it was blowing 65 degree air. It was not 75 in the cabin, coolant was at operating temp.

It seems to be working today.

It may be that I just forgot how it acts with a working AC compressor...

I am just going to monitor it for while, and see what happens when it really gets cold.

thanks for the responses.