2009 Nissan Frontier Intermittent A/C on 2 and 3 speed fan setting

forumjoe wrote: New twist Guys, I am now having intermittent A/C on fan speed #4 too. That does not go through the resistor pack according to the schematics. This just started happening over the weekend.

To be clear, the blower still keeps spinning on #4, right? Just the A/C light goes out, and the compressor disengages? If that's the case, I wouldn't sweat the relay.

I still think you need to watch the FR BLOWER circuit with a multimeter when the compressor disengages. We know there's some kind of pull down circuit at work there, and we know it comes from the BCM, and we know the BCM won't allow the compressor unless it likes what it sees.

Tyler,
Yes the blower fan motor keeps spinning on #4 but about a week ago the A/C switch light started to flash on and off, much like the #2 and #3 speeds, I was able to get it to stay on eventually but that never did that on setting #4 previously. I also should mention that when I was swapping and testing the relays, after I plugged them back in, the blower fan would not come on at any speed setting. So I went back to the blower relay and moved the wiring harness beneath it and the fan came back on, but I had to fidget with it to get it to stay on, so far it is still operating.
Okay so when I am looking at the BCM Air Conditioning data stream on my ThinkDiag scantool the fan switch says it is OFF but the fan motor is blowing away. I assume if the BCM sees or thinks the fan is"Off" it won't allow the compressor to engage, correct?

If it helps it was the resistor pack. I tested everything that I could, the fan control switch with my power probe as per Eric at SMA, I tested the fan circuit with my Load Pro per Dan Sullivan, I tested all the relevant fuses and relays. I back probed the motor while operating the fan and everything I checked tested out ok. I then pulled the resistor pack out and ohm tested the individual contacts with the common ground contact (the Blue Wire) and 2 out of 3 tested the same .001 ohms the red wire contact however tested .134 ohms this is the #1 setting on the fan switch which is also shared with what I believe is the signal input to the Fan Control Unit that tells the BCM if the fan is on or off so that it can then turn on the A/C.
I decided to purchase a new resistor pack from my local NAPA store as that is what Eric at SMA did for a Fan motor problem on a Nissan Frontier that he did a You Tube video on, if it is good enough for him than it is good enough for me.
I haven't tested the amp current draw on the motor but I might as I have read that a high current draw can harm the resistor pack.
Anyway, I installed the new resistor pack and all is working again so far, blower motor speeds are working and A/C button light is now working on all speeds seems OK but I will be watching for awhile.
I am attaching a pic of the old resistor pack that I took out so you can see what it looks like.
I hope this helps someone with that kind of a weird problem.

forumjoe wrote: If it helps it was the resistor pack.

It does. Thank you for the follow up, and congratulations on the fix!

I then pulled the resistor pack out and ohm tested the individual contacts with the common ground contact (the Blue Wire) and 2 out of 3 tested the same .001 ohms the red wire contact however tested .134 ohms

Are you sure about those resistance readings? :huh: Most meters I've seen can't measure down to .001, or even .134. Did you mean 1 ohm and 134 ohms? Because 134 ohms would be high enough to cause a voltage drop in a 12V circuit.

Tyler wrote: Because 134 ohms would be high enough to cause a voltage drop in a 12V circuit.

Resistor pack is on the ground side of the motor so there shouldn't be 12v there with the blower running. There may be a current limited voltage, from either the FAC or BCM, on the red wire which needs to be pulled to ground thru' the blower resistor. Not sure whether 134? ohms would be enough to affect that?

that was on the 2K scale of my meter

I don't know but everything seems to be working for now. I will know more in a few days use.

After changing scales on my DMM I get 1.9; 1.0; and 50 as ohm reads on the 200 scale of my DMM. The 50 ohm is for the red #1 setting lead.

forumjoe wrote: After changing scales on my DMM I get 1.9; 1.0; and 50 as ohm reads on the 200 scale of my DMM. The 50 ohm is for the red #1 setting lead.

Gotcha, thank you sir! Wasn't trying to sweat you, just genuinely confused for a moment.

forumjoe wrote: that was on the 2K scale of my meter

The meter was probably displaying in kilo ohms then. So your .001 readings were 1 ohm.

yes I think that is what happened