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

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3 years 8 months ago - 3 years 6 months ago #41247 by forumjoe
I have a 2009 Nissan Frontier 4 cyl 2 wheel drive that has started to act erratically. I have A/C light on and fan on in #4 fan setting but have no A/C light on either #2 and # 3 fan setting however the fan still operates as it should, the compressor/clutch does not work on these settings most of the time, I can however get it to operate on those settings sometimes. I have watched all your videos on the A/C subject as well as Eric's from SMA I feel I am close to figuring out an electrical problem but I am confused looking at the schematics for the truck which I am including here for your advice. You and Eric are the best diagnosticians out there. Short of taking the truck to SMA ( I live about an hour and a half away), I would like to try to fix it myself. I first thought the blower resistor might be the culprit but the more I thought about it I changed my mind as the blower fan works on all speeds as it should, the AC lights turn off and the compressor stops when I switch to #2 and #3 speeds but it will work intermittently sometimes. Any thoughts would help.

thank you
Forumjoe
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Last edit: 3 years 6 months ago by Tyler. Reason: spelling correction

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3 years 8 months ago #41251 by Hardtopdr2
This sounds like the fan speed switch is the issue. If you look at the schematics you will see 4 wires coming from the fan switch to blower motor resister. Now when you switch it to speed 2 or 3 it is fed in to a spot before and after a resister. Which if it was a blower motor resistor bad it would not work in that spot at all but rarely they will partially fail. To find this out you will need to back probe the blower switch and the blower motor resistor wires in each position. Then run vehicle till problem happens again and test each speed for power going to each speed and comparing that to the output wire for fan speed. The idea here is to see if the fan speed switch has bad comtact spots, if power gets interupted to switch, if blower motor resister has a bad resistor.
Now to expand on the blower motor resistor 4 speed will not have a resister slowing current flow. So if 4 speed works all the time and rhe other speeds are intermitant or not at all then i would lean that way. However with the a/c clutch be disabled that make me think the fan switch has an issue with either power feed or an open in the switch. So with the switch when it acts up see if your power feed is being interupted to the switch or if the is a problem with the power going through the switch.

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3 years 8 months ago - 3 years 8 months ago #41254 by Tyler
Can you give me a better shot of the BCM and the Forward Air Control modules in your manual? I'm trying to make out one of the circuit descriptions.



It's a shared circuit between the resistor, the FAC and the BCM. I can't find any reference to it in SI. :( But I can't help but wonder if it's involved, given that the blower continues to work even when the clutch is disengaged.
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Last edit: 3 years 8 months ago by Tyler.

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3 years 8 months ago #41255 by Tyler
Scratch that, I did find something in SI! HAC-108 describes checking for an inop clutch, and goes into checking this circuit specifically. It also has you checking BCM scan data PIDs.

I'd be very interested to check the voltage at pin #1 of the blower resistor while cycling through the fan speeds. Do you have a scan tool capable of communicating with the BCM?

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3 years 8 months ago #41262 by forumjoe
Tyler, I do not have a scan tool to isolate the BCM. Is there a way I can check it otherwise? Incidentally I took the truck out today and the A/C worked on both #2 and #3 fan settings, I could not get it to fail, I even purposely went over some pretty hard bumps to maybe jostle some wires or connections but nope it stayed working. I did however run a system scan with my ThinkDiag scantool before I started the truck and drove it. It failed communicating with the HVAC modules so I don't think there was anything available for this vehicle to monitor or test. Maybe coincidence? I don't know but I will test it again tomorrow and keep you posted.
Thanks for the input.

joe

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3 years 8 months ago #41263 by forumjoe
Hardtopdr2,
Thanks for the reply I think I was thinking the same thing as the resistor pack only controls the blower motor speeds I assume and has no effect on the A/C compressor lights on or off, but I don't know for sure if they are indeed connected through some of the other modules as Tyler seems to be suggesting. What do you think?

forumjoe

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3 years 8 months ago - 3 years 8 months ago #41266 by Hardtopdr2
It depends on system design.... most common is with a/c button activated and then fan speed selected there will be a signal sent to bcm or pcm to activate the a/c clutch via the relay. This signal can be sent via monitored current flow or signal wire or can bus signal. If the system has a digital read out of temperature it will be an auto air conditioning hvac which will have a module to communicate with scanner. This type might have a a/c signal wire to bcm or communicate through can bus.

A manual setup which has dials with blue and red color looking like a yin and yang will be manual a/c which most times will not have a a/c module. This setup will be run as far a data parameters though the bcm module and should have a a/c request signal wire from a/c controller to bcm. The signal for the clutch to kick on will be sent when fan switch is turned on when a/c switch is on. Whichever occurs last. This is why i suggested to look at fan speed switch (power feed and power to blower motor feed to isolate and determine if its the switch, the a/c button or the module that gets the a/c signal.

My hunch would be the switch is causing the issue however powers and grounds checks of bcm/a/c module if auto a/c. Typical problem areas are where water has been getting in like front floor board area ground points or near heater core/ cabin air filter area.
Last edit: 3 years 8 months ago by Hardtopdr2.

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3 years 8 months ago - 3 years 8 months ago #41267 by forumjoe
Hardtopdr2,
It is a manual setup, If I probe the blower motor connector at the motor should I get a power signal with a test light no matter what my switch is set at #1 - #4 ? and should I get a DVOM reading of different volts at the resistor connector? would that help to isolate where the problem is? Did you see my latest reply to Tyler? I drove it yesterday and A/C worked on both the #2 and #3 speed settings and I could not get it to fail. Bumped, jostled, bounced vehicle to try to get it to fail it didn't. I did run a system scan with my ThinkDiag scan tool before I drove it though. It would not communicate with the HVAC module however but maybe it reset something, I don't really think so though just a coincidence maybe. As for testing the BCM I am not sure where that is located to see if there is a signal when A/C is requested also where is the FAC located? Engine room or inside under dash?
Thanks
keep thinking
forumjoe
Last edit: 3 years 8 months ago by forumjoe.

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3 years 8 months ago - 3 years 8 months ago #41274 by Matt T

Tyler wrote: Scratch that, I did find something in SI! HAC-108 describes checking for an inop clutch, and goes into checking this circuit specifically. It also has you checking BCM scan data PIDs.

I'd be very interested to check the voltage at pin #1 of the blower resistor while cycling through the fan speeds. Do you have a scan tool capable of communicating with the BCM?


The diagram on HAC-109 and circuit check on HAC-110 doesn't match the full wiring diagram on HAC-120 showing the branch off to the speed #1 circuit. And although it's shown as an external splice it might actually be an internal connection inside the FAC. If it exists at all.

It does sound like the FAC is turning off AC because it thinks the blower isn't on. BCM PIDs would be nice to have but I don't think they're really necessary since the AC light is turning off. Will take voltage checks to figure out what the heck is going on. Ideally on the FAC but if the resistor is easier to access start there.

Joe,

The FAC is the HVAC controls in the dash. It doesn't appear to be networked so you're not going to see it with a scan tool.

Here's a link where you can get the factory SI Tyler and I are referring to.

www.nicoclub.com/nissan-service-manuals
Last edit: 3 years 8 months ago by Matt T.
The following user(s) said Thank You: Tyler

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3 years 8 months ago #41275 by Hardtopdr2
Yes you should see power at speeeds 1-4 and voltage should vary low to high as well. the best way is to use a currrent clamp on the blower motor power wire from resistor and you would see current increase as fan is turned to each higher speed. It should read 5 amps 10 amps, 15 amps, 20 amps for each speed 1-4 respectively. But i would recommend a subscription to mitchel1diy at www.eautorepair.net this will have better diagrams and will give locations of modules and connectors and ground locations for all equipment. It is well worth the money it will also have testing procedures in there to test the components and wiring.

I did see your post to tyler and with it being intermittent this could be a corrosion issue (power and ground wires) , a contact issue with switches or relays, a bad module, or a bad wire.
Since it is a manual a/c it should not have a a/c module however the mitchell diy site will tell you if it does have one or not. If it does then it could be that module is bad or has a power or ground problem.

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3 years 8 months ago #41278 by forumjoe
Thanks Matt, Tyler and Hardtopdr2,
I appreciate your efforts and the knowledge is a great help to me as I do not have the high level scan tools that some do. Thanks for the links you guys posted I will do some more research and see if the A/C stops again and let you know.

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3 years 8 months ago #41283 by Matt T

forumjoe wrote: Thanks Matt, Tyler and Hardtopdr2,
I appreciate your efforts and the knowledge is a great help to me as I do not have the high level scan tools that some do. Thanks for the links you guys posted I will do some more research and see if the A/C stops again and let you know.


Don't let the lack of a scan tool discourage you. It's really not needed for this. A DMM should be enough to figure out what's going on.

I also agree with Hardtopdr2 about getting an aftermarket single vehicle SI subscription. It might help clarify how the blower monitoring really works on this thing.

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3 years 8 months ago #41285 by forumjoe
Went out today and immediately no A/C #2 & #3 fan settings changed to #1 then back to 2 and it came on kept flickering light then went off again kept playing with settings and got #2 & #3 to come on and stay on. The flickering A/C lights on those settings makes me wonder if there is a loose wire or harness involved. I was able to reach up and get hold of the harness for the blower fan and the resistor pack kept moving wires and connector to see if I could change the A/C light to come on I thought I did by wiggling the resistor harness it came back on but ultimately went off and I could not get it to come back on after that. You guys are so smart I am hoping I can solve this without taking it in. I worry about that because there are so many parts changers out there in the shops I use.

Thanks for giving me the knowledge.
forumjoe

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3 years 8 months ago #41286 by forumjoe
I may have to resort to that just because I want to solve this

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3 years 8 months ago #41291 by Hardtopdr2
With the a/c light is it in the dash cluster or a seperate light in the a/c button? If its a button then follow those wires coming from that button to the module an check those for corrosion or a break in wire. You can do this with the dmm setting it to ohms and disconnect the two ends of harness and test the wires end to end. Red lead on one side and black lead on the other side of the same wire. Should read 0 ohms. if it reads more ohms or OL then there is your problem. Check both wires and look for green crusty stuff on connectors. Good luck

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3 years 8 months ago #41297 by forumjoe
Hardtopdr2,
It is a light in the A/C button I would think an led, I will ty to trace it to the module if I can find the module and read the wire in the schematics. Thanks I will try.
Joe

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3 years 8 months ago #41298 by Matt T

forumjoe wrote: Hardtopdr2,
It is a light in the A/C button I would think an led, I will ty to trace it to the module if I can find the module and read the wire in the schematics. Thanks I will try.
Joe


Your HVAC controls are the module, and the blower control switch. Hopefully you'll see a picture of the back side of it I borrowed from ebay, The connector top left with the spade terminals is your blower switch. Since factory SI doesn't do a good job of explaining how the blower monitoring really works you need to backprobe the terminals on the FACs blower switch connector and see if they're all reading 0V to B-, or close to it, when the AC light is off but should be on.

The following user(s) said Thank You: Hardtopdr2

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3 years 8 months ago #41318 by forumjoe
Pretty cool use of ebay I must say. You are very clever.
Thanks Matt,
joe

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3 years 8 months ago #41355 by forumjoe
Hi Guys,
Just running through all your suggestions and looking at the A/C schematics in the Chilton manual and thought if I probe the blower motor connector with my LoadPro tool from Dan Sullivan and cycle through all the blower switch settings while observing the voltage changes it would only tell me if I have an open or a short to ground or resistance in the wiring but would not take into accounnt the A/C relay and signal wiring of that part of the system, right?

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3 years 8 months ago #41365 by Hardtopdr2
Hey joe,

Can you get a closer pic of that wiring diagram? Not sure but it looks like it is ground side switched.

What i can tell is from the fuse it feeds into the relay then to the blower motor followed by the blower motor resistor then through the fan speed switch and finally to ground.

If that is the case check for voltage on the relay side of blower motor connection if you have power there and that voltage goes higher to (battery voltage) when it acts up then the switch assembly is the problem. If it drops to 0 when it acts up its a relay. To rule out a relay sway a good one from another circuit that you dont use like high beams or something and see if it still happens. From what i am seeing its relay or switch depending on the result.

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