paul4b

Help:
I just bought a new (used) fully loaded 98 SE with the automatic climate control that doesn't seem to work properly.

The unit seems to overcorrect way too much. For example, if I set the
temperature to 72 degrees, it brings the car to a temperature above 72
(feels like 80), and then slows the fan down & lets in cold air until
it feels like it reaches 60 degrees. This is a 20 degree swing, my
mechanical thermostat in my house controls temperature better than
that (I belive +/- 2 deg.) !!

Is their a gain or swing adjustment on the unit?
Is this unit's operation and/or calibration covered in the serivce manual?
Can anybody help me with this one, my commute is freezing me!

BTW, my 94 had that nice manual climate control (always worked perfectly).

Thanks in advance!

njmaxseltd

iTrader: (19)

Well first off it definately shouldn't work like that. Mine does an excellent job of maintaining the cabin temp perfectly. There are many temp sensors on that system, cabin temp sensor, outside air temp sensor, delivery air temp sensor and a ***Sunlight intensity sensor***. That sensor is located in the passenger side front window defroster vents. Looks like a shiny disc. Keep that sensor clear, if anything blocks it's view of light the climate control system does strange things.... It's possible that your sensor may not be functioning. There is probably a test procedure (digital readout???) that will tell you if the sensors are working correctly. You might need to get the dealer to have a look at it.

BluFlame

iTrader: (2)

Mine works very well, i cleaned the sensor inside the control unit.
and there is a sensor in the front, behind grill, check that its connected and not broken. Use economy setting, not auto for heating.
I think 95-96 climate control unit is little different than later ones but that's just cosmetic. i hope this helps.

paul4b

Do you have the shop manual for your Maxima?
Does it specify how to test the sensors and/or control unit?

Any help is appreciated.

Thanks,

Paul

Originally posted by BluFlame [/i]
Mine works very well, i cleaned the sensor inside the control unit.
and there is a sensor in the front, behind grill, check that its connected and not broken. Use economy setting, not auto for heating.
I think 95-96 climate control unit is little different than later ones but that's just cosmetic. i hope this helps. [/QUOTE]

paul4b

One more thing:

I'm trying to take a look at the interior sensor, I couldn't find the one mentioned by the radiator, but HOW do you take the radio & climate control bezels off???

I can't find a screw anywhere!

Thanks!

BluFlame

iTrader: (2)

You need to take the bottom pieces off first,shifter cover and lighter trim first, remove the top vents they just pop out. 2 screws on top, 2 at the bottom. there r many threads posted explaining how to remove the console.
i have no fsm, i use haynes manual. climate control is hard to fix.

njmaxseltd

iTrader: (19)

installdoctor.com has excellent instructions and pics on how to take our cars dash apart.

paul4b

Thanks for the advice.
I have the Chilton manual from my 94, it covers 98, no info on the Auto Climate Control unit either.

I'll take some ohm measurements this weekend on the sensor, perhaps someone has the factory manual??

Freezing in NY.

paul4b

Solved the problem, and learned something about the Auto climate control system.

The Auto Climate Control unit does not contatin a processor to regulate the interior temperature. The sensors are wired directly into the main harness going to the computer. The unit above the dash is a control unit only, you enter your desired temperature setpoint, and based on feedback from the computer, it controls the damper doors and hot water valves.

After pulling out the control unit, opening it up, and noticing that the interior sensor didn't get wired to the Circuit board, I realized that this unit was for setpoint & damper control.

My problem was that the interior temp sensor was supposed to have a hose pulling interior air over the sensor, and that hose was disconnected.

My interior went way over temperature because, the sensor took forever to 'feel' the interior temp, and it got too cold for the same reason!

Problem solved - Thanks for all the help guys!
The link to installdoctor.com was key!

Paul