Hey guys I have been reading all the great info.  Thanks to everyone.  I do not have a Frontier but I do have a 2003 Murano (after 3 Pathfinders ! ) 

Anyhow I have been having heat/ac blower issues since day one that are becoming more frequent and of course not reproduceable at the shop !  Luckily I have not paid for any repairs or diagnostic yet cuz I don't trust ANY NISSAN dealership !!!!  Everyone I ever encountered is a cheat.

Neither heat nor AC blows very well when on "feet".  BUT the Biggest issue is that when I need AC the unit seems to be cooling and blowing. It just blows someplace else but not into the cabin.  If I switch to defrost it will not blow either.   This is not constant but it is chronic.  It usually happens if I drive an hour or more but lately even 15 minutes will start it.  Sometimes we can fidget with the controls for a while and "force" it to blow again sometimes the vehicle has to be completely off and restarted and sometimes nothing works and it just starts blowing again.

From reading all the post my self diagnosis seems to be the Blower Motor resistor... but could it also be the TCA ???  Could I have a combo issue?

Thanks again

..

Welcome to the group!!!

For parts try;

http://www.nissanwholesaleparts.com/

http://www.nissanwholesaleparts.com/faq.asp

or

http://nissan4wheelers.com/eve/forums/a/frm/f/347106241

these places have a good track record!

lakota..

Great discussion on this TCA thing. 

I have the same symptoms on my 1995 D21 hardbody pickup.  I verfied the TCA is outputting 5 volts when the clutch is off and 0 volts when the clutch is engaged, and the ECM module is switching the ground connection to the AC relay accordingly.  The pressure switch is not opening when the AC cycles.  If my TCA is bad, it must be that it is switching at the wrong temperatures.  Is that the normal TCA failure mode?  Talking to several friends - some say its normal for an AC to cycle, others say no.  This one cycles every few minutes.

Regarding my TCA, I think I have a different one than what has been described so far.  My TCA is a black module 1"X1.5"X2.0"mounted on top of the evaporator box with the thermistor wires leaving the module and entering back into the evaporator box (towards the driver).  There is one three wire connector to the module - I believe it goes to ground, the ECM control line (thru the pressure switch), and to +12V.  The evaporator box has snap clips instead of screws, with snapclips next the firewall side.  It appears to be a real big problem to R&R the module and thermistor.  Does anyone have any experience on this model?

Judging from the pictures in a previous post, the replacement part (red thingy) has no associated electronics, ala my black module.  One web site (courtesy, I think), showed the same part number that been quoted here as a replacement for mine.   Again - more confusion.  My local dealer says $85 for mine.

Does anyone have insight, or advice?  Thanks for some great feedback on the site.  (I just joined!) 

Florida Spacecoast

Hello. I registered to say that even if 50 certified master mechanics on this forum say that they do check the thermal control amp, I think it's just LIP SERVICE! 

Check all the forums out there regarding this issue. There must be several hundred people that went to Nissan certified repair facilities to have this intermitent AC issue rectified, and after hundreds of dollars if not thousands, had the same problem after the repairs by Nissan. I am one of those people. I replaced the TCA after Nissan replaced my compressor and high pressure switch for nothing! The stupid $39 dollar TCA was the issue all the time.

HOW CAN THESE NISSAN CERTIFIED MECHANICS BE SO OUT OF TOUCH WITH THIS ISSUE? 

WHY DOSEN'T NISSAN HIRE PEOPLE TO MONITOR THESE FORUMS?

If they did they would learn alot.  I know I did.

Xtrudes.

Solved!!!

First, I proved my TCA was bad by verifying the dual pressure switch is staying closed while the clutch cycled.  Second, I drilled a small hole in the output side of the evaporator case and installed a small themometer and verified the temperature was about 40 degress and cycling - but never close to the 32-34 degree cutout temperature.  Sure looked like a bad TCA.  My electronic experience told me thermistors are passive components and shouldn't go bad.

I was able to remove my TCA with a right angle phillips ratchet and was able to get to the printed circuit board.  I unsoldered the thermistor wires and took the PCB to the bench where I replaced a BA10358 Op Amp IC with an MC1458 (standard run-of-the-mill Op Amp) - about 50 cents.  Put everything back together and all is well.  Now really cold.  Exit temperature is about 40 and never cycles.

Saved a bunch of money by being persistent and getting some good tips here.  Keep up the good work and thanks!

LPSEngineer

Hello All, thanks in advance.  Similar to all symptoms above (cools, then stops cooling, sometimes not coming back to cold), I replaced the TCA following all posted instructions.  Was really careful and removed and replaced with new TCA but unfortunately still having the AC get warm and stay blowing hot air.  2004 Nissan Frontier.  Suggestions appreciated?