With that being said, This post is about opening these blend door actuators up and replacing the electric motors that are failing after 30+ years of wear.
Tools/products required:
-Screwdrivers, flat head and phillips
-Soldering Iron
*lithium grease
*electronics cleaner
*Electric motor # RF-370CN-14420
(big note here- Due to the age of these motors, even the electric motors are getting hard to find, but worry not, there are still options. The ones I used are the modern production I pulled from amazon, and the last example I could find with the exact OEM part number ( https://www.amazon.com/dp/B0CN6389JP?re ... asin_title ). If these motors specifically with this part number become unavailable, you can use some with similar specs that are still in production for hobbyists. These are the original specs for these motors:
12V-18V DC
8800RPM
24.2mm~ diameter
30.7mm~ length
17mm from screw hole to screw hole using an M3 sized screw
2mmx8.4mm shaft
One example I found that could potentially work was an updated part number (RK-370C-20190) which are set with the same dimensions, but are 9800RPM and run at 5V-12V DC.)
To start, the information of what it takes to pull these is already available on here and other places, so this will focus solely on fixing the actuators and putting them back in. Along with this I will put a disclaimer that it is always good form to take photos of every step of the process so if you have any questions that I cannot properly articulate here, the visual reference may offer insight to how something went back together.
The first one I'll cover is the air circulation actuator on the passenger side:
1.using a scribe, make a marking on the actuator's arm and brass dowel that it sits on so you can recall where the arm sits. if you can't remember where it sits (like you forgot or didn't make it noticeable enough like I did the first time), you can still find where it needs to be using a technique I'll have in step 8.
2. with a screwdriver, undo the three screws on top holding both the actuator to the mounting plate and the housing.
3.With a flathead, carefully lift up each tab around the housing; if you're lucky the tabs will stay up on their own allowing you to handle each. If you are not so lucky, put a little bit of force on the seam holding the two parts of the housing together and that should get them over. If you break one or two of them though, it's not the end of the world. I had broken one of them, but the screws will hold the housing together anyway.
4. Pull the housing apart. Once exposed, take note of where the gears are located and in what orientation. Failing that, this photo gives a pretty good idea of how it all fits together.
Start by removing what gears you can, all but one should come out, with the one being just off center enough to be stuck under the electric motor's shaft. While you can get it past the motor shaft barely, you may run the risk of breaking the plastic shaft that the gear runs on, which the opens a hole other can of worms involving plastic repair that most would like to avoid.
From here you will see on the back end the two prongs that are soldered to the control board. Pull your soldering iron out and de-solder the two prongs, separating them from the contacts on the motor. From here you can pry the motor out with its mounting plate, and pull the last gear from the housing.
5. With everything laid out, feel free to clean all the old lithium grease from the gears and housing. pry the worm gear and unscrew the mounting plate from the old motor. I have this photo here with all parts laid out once fully disassembled
6. Once all is clean, begin with applying the new lithium grease to the contacts of the housing at the bottom and bottom contact of the large gear. Grease and place the gear that cannot be removed without removing the motor FIRST, then screw the mounting plate to the new motor.
I recommend bending the contacts on the housing back into place before slotting the motor into place that way you are not working against the tension of bent metal as you are soldering everything into place.
After soldering the contacts to the motor, all that's left is to grease and put all the gears back into place. I used a mix of a toothpick and my finger to apply the grease to the gears, making sure that there are no places that are completely dry, the most important part to grease will be the worm gear on the motor that interacts with the first gear.
Note: before this next step, go ahead and make sure everything is moving smoothly. To do this, you can use a car battery and some small alligator clamps or probes. connect the probes/clamps to the battery, then put the negative to the bottom connector of the motor, and the positive to the top.
This should give you a chance to see all the gears moving and make sure the motor is working without being overly taxed. Don't make the same mistake I did and reassemble it before doing this, as you will see in the other actuator's case.
7. reassembly is the reverse of disassembly; all gears in place and greased, put the top half of the housing on, making sure to put a little bit of lithium grease in the cup that the gear shafts will be pressed into, and press it together, making sure the tabs are all clicked into place.
Next, screw the mounting plate to the actuator.
8. The important part here is the arm and actuator dowel need to be pressed together in the same spot when you started. If you do not remember where the arm sat before, or forgot to mark where the arm sits- connect the actuator to the car (no need to bolt it in yet), then press the air circulation button so that it goes through its cycle once, then press it again. Whichever setting you have it set to, use that as your reference for where the blend door should sit.
You can grab the rod of the blend door to set it to the position that matches to what setting the climate control is at, then putting both the blend door actuator and arm in, you can find where the arm needs to be placed by placing it in a spot where you don't need to move the blend door to make it fit.
Past this, if you need to fine tune it, you can disconnect the rod from the clip that holds it and push or pull it out.
9. Once you have it in, put some lithium grease on the arm where it interacts with the blend door to prevent wear, and press the button a few times to make sure everything runs smooth.
Now with the air controls actuator that sits on the driver side:
Things are much the same way- disconnect it, take it apart, clean, and reassemble- but I want to take this one to describe an issue I faced that you may very well have too.
So for reference photos, here is the air controls actuator from initial disassembly to all parts laid out:
So I went through the process of disassembly, but noticed that the first gear that interacts with the motor's worm gear was real tight. I thought nothing of it because there was nothing I thought that could have caused it to tighten if it wasn't already like that. I soldered the new motor in, and reassembled it, but I did not check to make sure everything was running smoothly before I put the actuator back together. Now I don't know which one actually caused what happened next, the motor being bad out of the box or the first gear being tight, but it could have been prevented if I tested it before putting in the car.
I hooked up the actuator, turned the car on to test it, and nothing happened.
I didn't hear the actuator move or anything. Well in the time it took me to look at the actuator and press a few buttons on the climate control, the climate control box let out the ghost. Smoke started pouring out and got real hot. I turned the car off and disconnected it, but the damage was already done. The buildup of current from the jammed/dysfunctional motor backpedaled into the resistor on the board, and caught fire. The photo here shows the damage
I was incredibly lucky I had a spare from a parts car that I pulled from not even a day ago, but considering what I said before about parts rarity, this is going to be unlikely for people in the future.
I want to bring this up too, as nissan in their infinite wisdom changed the entire board layout from '89-'90, which means nothing if you're swapping boards, but if you want to repair a board and cant recognize what the burnt resistor was, and think you have a reference board, it makes an unpleasant surprise
After this happened, I had done a troubleshoot of the actuator and found out the original motor was actually still good, with the new one not working beyond just weakly turning with no torque. On top of this, once I hooked up the original motor and found it wasn't turning the gear, I went to opening the hole of the gear, greasing it again, and that solved the issue.
If you have any excess friction in the gears, you can use a dremel and a drill bit of approximately the same size as the hole, and roll it with the bit in the gear's hole to prevent it from being uneven.
aaaaand that's it. While this post was for the 240sx actuators, I am confident that most other nissans around this era will follow a similar procedure, meaning if your R32 or Z has the same problem, you may just be able to fix them yourself!
Please let me know if this helped you. I would like to see more fixes like these for components as it gets older and harder to find. At the time of this post I'm in the process of modifying a chassis harness from a manual hatch to replace an automatic coupe's, making it so my coupe has all the wiring for a manual. if anyone would like me to make a post of this process too let me know.
