1997 Q45 No heat, trouble code -26

Post by **fontana dan** » Tue Sep 27, 2022 10:14 am

Hello folks,

Yesterday it was a little chilly so i tried to use the heat in my Q for the first time. Surprise, no heat whatsoever. AC blasts out the vents with temp set at 85F on hvac control. Self diagnosis returns code -26 "Air Mix Door Motor PBR."
First off what does PBR mean?
I've located the component and pinpoint test in the FSM for '97 but unable to find full electrical schematics or connector view for HVAC system.
Any advice on this before I tear into the dash? I see the motor is supplied 5v from a module called "HVAC Amp." What is that?

Post by **VStar650CL** » Tue Sep 27, 2022 10:36 am

PBR = Precision Balance Resistor
The mix door actuator is basically a garden variety servomotor with a built-in feedback potentiometer (pot) that tells it what position the mix door is in. The problem could be an open in the wiring, but most likely it's just a bad pot and you need to replace the actuator.

Post by **fontana dan** » Wed Oct 05, 2022 3:56 pm

Thank you for the input VStar.
I found the full electrical schematic and was able to test the circuit with a multimeter. Key on engine off. Unplugged air mix door actuator connector M43. Probed connector M43 pin #3 found steady 5v.
+/- 10V on pins 4 & 5 on connector M43 depending if climate control is set at 85F or 65F. Seems like the circuit is functioning from the auto amp.
Testing the actuator component itself I get 200ohms across pins 3 and 1 for the PBR with door stuck at full cold. Was not able to find any continuity across pins 4 and 5 for the motor...thinking that could be an issue. Ordering a new air mix door actuator p/n 27732-70F00.

Post by **VStar650CL** » Wed Oct 05, 2022 5:20 pm

The motor brushes or nylon gears are always the prime suspects with actuators, whether you're talking about HVAC or headlight aimers or anything else with analog movement control. Since the late '80's they all use "toy boat" sealed brush motors with monster gear reduction, and none of that stuff lasts forever. Chances are your motor brushes are simply gone.

Post by **fontana dan** » Mon Oct 10, 2022 4:27 pm

So I removed the old actuator and it started working from being jostled around I guess. Reinstalled and I have heat now.

Post by **VStar650CL** » Mon Oct 10, 2022 5:01 pm

Hope it stays working, but it probably won't. That isn't much different from whacking a balky starter motor, the next time it lands on the same bad brush you get another no-start. That isn't graven in stone, but some finger-crossing will definitely be in order.

Post by **fontana dan** » Tue Oct 11, 2022 11:07 am

Yeah I have no clue how long it will continue to work. Finger-crossing is in order.
Also appears there may be another issue with the car unable to maintain a steady operating temp in cold weather(45F). Will keep a close eye on that.
But for now the cabin is warm. Thanks for the help vstar.

Post by **Q451990** » Tue Oct 11, 2022 8:36 pm

fontana dan wrote: ↑
Tue Oct 11, 2022 11:07 am
Also appears there may be another issue with the car unable to maintain a steady operating temp in cold weather(45F). Will keep a close eye on that.

I would replace the thermostat. The rubber seal around the edge will deteriorate, and let some coolant bypass it when it's supposed to be closed.

Post by **fontana dan** » Sun Oct 16, 2022 12:42 pm

That did not last long. New air mix actuator on order from this site after they cancelled the order days ago...

https://parts.sawgrassinfiniti.com/p/IN ... 70F00.html

Post by **fontana dan** » Tue Oct 18, 2022 5:01 pm

Actuator on indefinite backorder from that website. I know some dealers have the part across the country but they want like $300+ for it.
Going to go to the junkyard when I get a chance, to get a spare air mix actuator from a 90s Nissan for some experimentation.

Post by **chrisbr66** » Fri Oct 21, 2022 11:06 am

Hi, I'm also replacing the actuator in my car also. Any hints to getting it out? I'm having a hard time getting the top 4 screws out

Post by **fontana dan** » Fri Oct 21, 2022 7:15 pm

I'm attaching a picture of the mix actuator. It is directly next to the gas pedal, a black piece with white arm and pink wires on the electrical connector.
In my '97 it is held onto the bracket with 3 8mm hex-head screws. You can use a short 8mm box end wrench, or a low-profile phillips head socket to remove it. To remove the connector you press the tab downward.
In this picture the metal rod on the left is the gas pedal. Air mix actuator is the dusty thing.
I found a '99 Q45 in a junkyard but the part was different on that car. bummer

Post by **chrisbr66** » Mon Oct 31, 2022 6:21 am

Hi Dan, thanks for the info and pics. The one screw towards the back right back was a pain to get to but finally got it. Replaced the actuator and now have heat, just in time for the winter. I will wait on the AC compressor replacement until the spring. Thanks again.

Chris

Post by **fontana dan** » Wed Nov 02, 2022 8:49 am

Hey chris. Where did you buy the replacement actuator? I've been looking around for a used one, but as it gets colder and colder here I'm thinking about coughing up the $$$ for the OEM part from the dealer.
By the way, if anyone has a 97-98 Q45 sitting around with a good air mix actuator and wants to send it to me...I will pay.

Post by **chrisbr66** » Fri Nov 04, 2022 8:38 am

infinitipartsdeal.com I paid 156.00 for mine, got it pretty quickly

Post by **fontana dan** » Sun Nov 27, 2022 1:57 pm

Ordered a new actuator online from a local Nissan dealer. About $190 out the door, heat is good now.

1997 Q45 No heat, trouble code -26

1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Re: 1997 Q45 No heat, trouble code -26

Nissan Forums

Infiniti Forums

Datsun Forums

Technical Forums

Classifieds / Marketplace

Nissan Motorsports

General Forums