98 Q45 climate control

[valq45man]

Hello,
I have a 98 Q45 and the climate control isn't working too well. The a/c basically stays on unless I put the temp on 85 (max heat). Otherwise it always blows cold air ! I've basically had this problem for quite a while but just ignored it. Has anyone had this problem before ? I've been using Google but I can't really find any information on this issue... ?

Any help would be greatly appreciated !

[Infinitiguy19]

First check to make sure all the functions of the electrical system part of the Heating, Ventilating, and Air Conditioning (HVAC) function properly by performing the tests shown in the service manual (Really simple): http://www.nicoclub.com/FSM/Q45/1998_Q4 ... Q45/ha.pdf.

I am not really a HVAC specialist so besides the above I would wait till someone more experienced comes in and posts.

[valq45man]

Thanks very much for the help.
It appears it could be the in-vehicle sensor still showing 97 degrees. The Ambient temp sensor is showing 96 degrees. The intake sensor is showing 131 degrees (seems wrong also). The car has been sitting in the garage now for over an hour.

Does anyone know if the in-vehicle sensor can be cleaned ? Or how difficult is that to replace ?

[Infinitiguy19]

Well I found one picture of the in-vehicle temperature sensor but it looks like its under the dashboard maybe on the right (Passenger) side. The intake sensor is a little harder to get to as its on the cooling unit to the left of the blower unit right behind the glove box.

Do you have a spare HVAC Control Unit (CU) to swap in to rule anything out?

[valq45man]

Unfortunately I don't have a spare HVAC cu. I did also see where it shows a 25 on the Sensor circuit test indicating a malfunction in the Sunload sensor. But I also read that this is wrong since it needs to be performed outside with sunlight instead of in my garage... ?

I'll keep looking to see if I can find where these are located and see how expensive they are.

Thank You...

[elwesso]

How far off do you think the readings you got from the sensors are?

I remember that when I looked at a couple of my sensors that one was completely covered in fuzz.. it would certainly be worth the try to clean them, only thing your out is your time..

[valq45man]

I really have no idea where these sensors are so I'm not sure what is involved.

I re-check this morning and the Sunload sensor tested out OK when outside in the sunlight (previously showed code 25 in my garage).

So after more thought, every time I re-check the sensors the Intake sensor always shows 131 degrees constant. The others do adjust somewhat.

Does anyone know where the Intake sensor is (according to the HVAC diagnosis) and how difficult it is to replace ?

Thanks to everyone for their help !

[elwesso]

the intake sensor is located on the downstream side of the evaporator..

Its most likely short circuited because resistance goes down as temperature goes up..

http://www.nicoclub.com/FSM/Q45/1998_Q4 ... Q45/ha.pdf

go to page HA-71... That shows about everything. it does not look like its going to be much fun to replace, but its possible it may not be too bad. it seems that I recall on the G50s that the cooling unit is a 2 piece setup, so you might be able to only remove the bottom part so you dont need to remove the evaporator..

Personally, for a temporary fix so your AC works fairly normal I would get a couple small resistors from radio shack.. I think a 2 k-ohm resistor would do it.. Just unplug the sensor and put the resistor in the 2 terminals..

[valq45man]

I called Infiniti Parts here in Houston asking them for an "Intake" sensor for the A/C climate control system and the guy thought I was crazy. I referred him to the manual I was looking at and he thought I might be talking about a Themistor sensor.. ?

I'm not much on all this sensor stuff but it was only like $16 so not bad at all ... If indeed we're talking about the same thing...

[elwesso]

What was the part number he came up with?

[valq45man]

I just called back and he said the part # is 277234P000 .. $16.49

From what he was describing in his diagram it sounds like the correct sensor.

[elwesso]

Yeah thats the one... I would go ahead and buy it.. Even if you just plug the sensor in and dont take anything apart to put it where its supposed to go, its still gonna work better.

[valq45man]

Right. Any ideas on what the correct reading should be on that sensor ? Is that actually checking air temperature and reporting back to the control unit ?

[valq45man]

I did get the part and I will try to figure out how to swap out old sensor this weekend.

Thanks very much for all of your help.

[valq45man]

Well looks like this has solved my problem. Thanks to everyone for their help !

[elwesso]

were you able to get inside there and put the sensor in its proper place, or what did you end up doing for the repair?

[valq45man]

No - I basically just removed the old sensor and inserted the new one into the box as a temporary fix. That looks like a lot of work to remove the entire evaporator (I think that is it). So for now that will have to suffice. I may get more motivated in a few months when the temp drops from 98 to 60 or so here in Houston - and fix it correctly.

As soon as I installed I ran the tests and it showed a much more believeable reading than a constant 133 degrees (I think that is what is was showing).