New owner with ventilation problem

The tambour does move freely (with actuator not installed). There are some spots with minor resistance, but I attribute that to the seals inside still being somewhat functional. I don’t think I tested it through 360°, but I’ll double check that once I pull the actuator back off.

I wonder if there is surface corrosion on the connector from it being unplugged for an unknown amount of time.

I can test potentiometer values, however I want to make sure I don’t burn out the motor or break the gears if I leave power applied when it reaches the physical stops. Do you suggest applying power to the motor to move it to one extreme, then disconnecting power, then testing resistance on the potentiometer? Maybe I’m misunderstanding how the limits of rotation are controlled. In my mind, that is an ECU function with physical backups.

 

You could do that. When I tested mine through the full actuator range, the ohmmeter tended to hunt a little, so it was hard to look for dead spots in the pot, so probably not so helpful to leave the ohmmeter hooked up.

Not sure either. I don't know if the ECU learns where the pot endstops are during the first power on calibration.... or uses constant feedback from the potentiometer simply to make sure the already set resistance range values (in the ECU) are achievable.

 

No idea. Probably if you plug and unplug the connector a few times, it will help clear any surface corrosion. Maybe use some DeoxIT D5 at the same time.

 

I’m trying to locate my DeoxIT. I used it on my exhaust bypass valve solenoid with great success. I’ve reorganized the garage since then and some things are proving hard to locate

 

Stupid question of the day. How do you unplug the yellow connector on the HVAC ECU? I doubt there’s any continuity issue on the wiring to the actuator, but it’s something to maybe check later. I tried to unplug it earlier, but I wasn’t familiar with that style of connector. Also, after a drive to the grocery store, still no change in functionality. No surprise.

 

Is it one of those connectors with a small black plastic "saddle" on top of the plug? If so, lever it away from the ECU (about 3/8"/1cm). Then pivot the plug away from the ECU.

 

It is. That was my initial instinct, but I didn’t want to start prying without knowing for sure. Thanks.

 

Not sure which brake system you have.... If Teves, the ECU will be located here

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(EDIT: Sorry, crossposted)

I see you have an F1 car, so Bosch brakes.

 

Is that a RHD car? Same connector, but very different orientation. Helpful, nonetheless.

EDIT: I see. Mine is a Bosch car. Helpful, nonetheless. Same connector.

 

I already had the white (maybe technically clear) connector off the ECU, but hit a road block at the yellow connector. I checked the 10A fuse and it was fine. The larger (30A?) fuse didn’t seem worth checking since I think it’s associated with the blower, which is working fine.

 

Just make sure the fuse or fuseholder isn't melting. It can still be intact, but cause issues, but as you say, if the blower is ok, it should be ok.

 

I’ll double check, but a cursory check didn’t look abnormal. A lot of this will have to wait until later in March due to work, but I’m excited to have another problem to solve on the car. As silly as it sounds, I get kind of bored when the car doesn’t have any real issues.

 

Ordered some new DeoxIT and applied it to the connector with no result. While doing this, I noticed one male pin (actually the +power pin) was recessed significantly and was likely not making contact with the female portion of the connector. I reseated that pin, applied DeoxIT and plugged it back in. Still no success.

I went a little bit out of order from what I said my diagnosis process would be, but I tested voltage on the connector coming from the ECU. I tested the pin that would connect to the red wire on the actuator and connected the other lead to a chassis ground.

Here are the results. You can hear me cycling through different selections for air direction. Not sure what this accomplished, but it does appear some (very low) voltage is being applied by the HVAC ECU.

https://youtube.com/shorts/kLK6C87GSVI?si=JGHmPi-R1I1WeCxn

 

Not 100% sure what's going on here. The red and black wire do control the motor, but I suspect that the ECU doesn't know in which direction to drive the motor (as it doesn't know where the potentiometer/tambour is). Note that the polarity on the red and black wire changes depending on which direction the tambour has to go.

Could it simply be that the chassis is not part of the circuit, so there is no proper voltage reading?

 

Yeah, definitely not the most useful test, but it was easy enough to try before I pull the actuator back out. I just wanted to see if there was any voltage being applied at power-up. Maybe I’ll try the same test with the pin connecting to the black wire on the actuator to compare. As you said, a chassis ground may be worthless. I know somebody previously discovered that the ECU itself switches ground on this circuit, so not sure if a chassis ground accomplishes much. Anyway, just putting the info out there for whatever it’s worth (or not).

 

Bench tested the actuator with a 9V battery. I can hear the motor itself running, but the output shaft does not turn. Reversed polarity and the result is the same. Don’t know if the gears are busted or what, but I guess I’ll have to do a little surgery to investigate. No resistance readings yet as I didn’t want to run the motor much without any idea what is happening inside. Even though the actuator is NOS, I figured there was a chance it would not work.

Any advice on the best way to disassemble the actuator without doing unnecessary damage would be appreciated. I know the info is in a thread somewhere, but might as well try to get as much into one thread as possible.

 

Was your old one missing... I forget. Wouldn't it be best to try to repair your old one and return the NOS item?

Haven't opened my actuator case, but looking at photos, it looks like it involves dremeling the heads off the plastic nails. What damage you do during this process probably determines how you put it back together, rewelding plastic.... or drilling holes and using self tapping screws to reclose the case.

 

Yeah, my original one was missing, so I’m stuck with this one.

 

This isn't the dash actuator but is the same except for the potentiometer. You need to cut around the seam to separate the top and bottom.
The red arrow points to the gear that goes bad.

But note, this is a vert high gear ratio. So if you ran it a lot against a dead stop you might have stripped the gear.

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Perfect, thanks. I only gave it momentary power with the 9V battery. It did not move even a millimeter when it was hooked up to power in the car. Based on where the tambour is positioned with the actuator hooked up, the actuator is not against the physical stops. Based on all of that, I don’t think I did any damage to it, but it’s hard to say. Hopefully the problem will be obvious when I get inside to look.

 

If you look at the top picture you can see 4 small plastic "legs" with the shaft in the middle. The potentiometer chip mounts on those legs.

 

I had opened several. Do not cut the actuator into halves if you want to put them back like original.

Long in short, since it is only glued, use heat gun to warm up the four corners where plastic rivet are, use knife to cut off the portion above surface, insert a flat screw driver into the hole where the wires go through and start to pry from here gently and slowly one by one,

Depend on the skill and luck, sometimes the pin/rivet will successfully come out but sometimes the pin will broke but that is fine as long as the lower and upper case edges are complete and undamaged. Just glue them back with no opening traces.

However, I do see people drill and use screws to put upper and lower case on.

There are other plastic rivets inside to open if you want to take the cracked gear out, same way.

 

Great info, thank you.

 

I used your suggested method and got the case to open. I had hoped to easily spot the problem and, well, see for yourself if you can find anything wrong.

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I’m no genius, but I think I found it. I hoped this wouldn’t be the case on what was advertised as, and appears to be, a NOS part. Like the timing belts, this gear looks to deteriorate over time whether it gets used or not.

All of the plastic posts remained intact during disassembly and I expect reassembly will go smoothly. A certain someone has just earned a sale on an auction website

 

Ugh. I can’t figure this out. I have a spare NOS actuator and it is fine. Even using a 9 volt battery to operate it, I can’t resist the torque of the drive shaft with my fingers.
Anyway, it looks like a few people on the forum are offering repair services.