smashedpumpkins

My 2000 Nissan Maxima seems to be having some AC/Heating issues. It started out sporadically going out until it finally stopped working. (I don't recall if all settings worked or just high) I followed some instructions provided by DennisMik which I've quoted below. After some research I assumed my resistor/amplifier was bad but after trying DennisMik's instruction I'm a bit confused. I have the automatic AC controls.

I pulled the glove box, unplugged the connector from the fan control amplifier and grounded the blue/white stripe wire. The fan kicked on at high settings. Well DennisMik's instructions assume the fan won't kick on when I ground the wire. So I'm not sure where to go from here.

I still went on and did some more of his tests. With the connector plugged in, I measured the voltage of the thin blue/yellow strip wire and it read a constant 10.6 volts regardless of what speed setting I set the controls at. At the end of the quote below he says "If the voltage readings don't change then the control panel is bad." Is this still the case if the fan kicks on when I ground the blue/white wire as I did earlier? What part is the control panel he's speaking about?

So where am I at? I obviously don't know what I'm doing. Any assistance is greatly appreciated! Thank you.

DennisMik's original post. http://forums.maxima.org/4th-generat...maxima-se.html

RR5

iTrader: (6)

Take a look at the FSM link in my signature. You will find all the diagnostic procedures, check those and let us know the results.

DennisMik

iTrader: (2)

It appears I did confuse you. Re-reading my my post, I used the wrong word.

In the section where I say ground the wire and see if the fan runs, I wrote "The fan should run at high speed. If it doesn't, then either the fan control amplifier is bad (most likely) or the control panel is bad." The word doesn't is the opposite of what is should be. If the blower motor runs, the motor is OK and the control circuit (comprised of the fan control amplifier and the control panel) is the problem.

The control panel is the thing in the dash below the radio with all the buttons and switches to make the heater and a/c work. Nissan calls it the a/c auto amplifier.

The voltage measurements on the thin blue/yellow wire are for a working system. The fact that the voltage readings you got never changed, this would say that the control panel under the radio is bad. But before you go and buy a VERY expensive part, let's check that fan control amplifier module that is only expensive.

It would be much easier to do if you take the fan control amplifier out of the car. When you look at the module, the pins are numbered as follows:
We are going to check the resistance (ohms) of the transistor in the amplifier module. This will require you to to reverse the meter probes each time you measure between two pins.

black on pin 1 to pin 2 = 13.1M
red on pin 1 to pin 2 = infinity

pin 2 to pin 3 - 2.22 K both polarities

black on pin 3 to pin 1 = 0 ohm
red on pin 3 to pin 1 = 2.2K

If you get these readings on the fan control amplifier module, it is OK. That would verify that the control panel is bad.

smashedpumpkins

I measured each of the pins using the 20M and 200 setting. In both cases I don't seem to get any of the results you mentioned. I wasn't sure which setting to use either. Seemed like 200 for the 2.2k and 20M for the 13.1M but I did both settings for all. Just for reference, I've added an image. (Click it for a larger picture) Does this mean it's my amplifier that's bad? Thanks!

Multimeter set to 200 OHM
-----------
black on pin 1 to pin 2 = infinity
red on pin 1 to pin 2 = infinity
pin 2 to pin 3 - infinity both polarities
black on pin 3 to pin 1 = infinity
red on pin 3 to pin 1 = infinity

Multimeter set to 20M OHM
-----------
black on pin 1 to pin 2 = infinity
red on pin 1 to pin 2 = infinity
pin 2 to pin 3 - infinity both polarities
black on pin 3 to pin 1 = Goes to 20 and stops
red on pin 3 to pin 1 = Goes to 20 and stops




I started the process and got a little lost when it said to test other connectors and I wasn't sure which way to probe the connector. I jumped over to Dennis's process.

Step 1 = Yes
Step 2 = Yes
Step 3 = Yes
Step 4 = Yes black to 2 red to 3, No black to 3 red to 2
http://www.nicoclub.com/FSM/Maxima/2000/ha.pdf

DennisMik

iTrader: (2)

You need the fan control amplifier module. It is the most common part to fail. The pin 1 to pin 2 measurement is the path for the fan motor to ground. With this being infinity, the transistor inside has blown like a fuse.

In some respects I wonder if you were getting the proper readings. What you sometimes have to do is kind of scratch the meter probe into the contact pin because of a light layer of corrosion that can build up. Also you might have to wait 5 seconds or so for the capacitors inside the module to charge up before you get a reading.

Another question in my mind is the settings on the meter. The 20M setting was correct for the pin1-pin2 test. But the 200 setting is what I wonder about. Does your meter only have the 2 settings? Regardless, if you used the 20M setting, then the pin2-pin3 reading would display as .22 It would be nice if everyone had the same meter to eliminate doubts like this.

smashedpumpkins

Thanks Dennis. It's very possible I'm doing something wrong. I tried it again and still received the same results. The multimeter is an Innova 3306. I've included a video of me performing the checks. Hopefully that clears it all up.

DennisMik

iTrader: (2)

The video does answer some questions, so thanks for posting that. In the video you did the pin1-pin3 measurement and got a reading, something your earlier post said you didn't get. From your earlier post where everything came up as infinity, I was wondering if maybe the meter was malfunctioning. So now that doubt has been put to rest. The pin1-pin2 reading continues to show an open emitter to collector circuit in the transistor, so it is blown.

The only advice I would like to give you is whenever you go use the ohmmeter, touch the 2 leads together to see if it shows a short, 0 ohms. That way you know the meter insides are working and there are no blown fuses inside. Do this for each range as they are separate circuits in most meters.

smashedpumpkins

Thank you very much sir! I appreciate you taking the time to help out a stranger like myself. I went ahead and ordered a new auto AC resistor on Amazon for $60. I'll report back once it arrives. I'll be sure to test the meter for now. You learn something new everyday.

smashedpumpkins

Worked like a charm. Thanks.