P38A blend motor

wammers · Mar 29, 2020

kermit_rr said:
Yes I've done the calibration, which cycles from current position to cold, then hot and stops

Calibration is when the flap is taken in both directions against the stops and the motor is stalled in either direction. This gives the system info about the null point of the pot. Did you line up the flat on the drive flange with the top of the case then line up the arrows on the gear and pot?

kermit_rr · Mar 29, 2020

wammers said:
Calibration is when the flap is taken in both directions against the stops and the motor is stalled in either direction. This gives the system info about the null point of the pot. Did you line up the flat on the drive flange with the top of the case then line up the arrows on the gear and pot?

The replacement pot i put in had different alignment so the arrows don't line up, it's 90° out so i took that into consideration when i put it all back together

Datatek · Mar 29, 2020

kermit_rr said:
The replacement pot i put in had different alignment so the arrows don't line up, it's 90° out so i took that into consideration when i put it all back together

So for sure it sounds like a timing issue.

kermit_rr · Mar 29, 2020

It's ok, don't panic, being a Muppet as usual! Since i last checked (this morning) the pot is acting up!!

Doh

kermit_rr · Mar 29, 2020

Taken it apart again and the pot is working fine, the solder joints are fine and the wires are fine, yet nanocom was seeing wrong values that it wasn't seeing this morning. I wonder if there's a dodgy connection elsewhere...

kermit_rr · Mar 29, 2020

kermit_rr said:
Taken it apart again and the pot is working fine, the solder joints are fine and the wires are fine, yet nanocom was seeing wrong values that it wasn't seeing this morning. I wonder if there's a dodgy connection elsewhere...

Yep dodgy connection somewhere. Put it back on the car and it worked for a few moments ie. Moved as i changed the temp on the car display, then stopped.
Progress i think, guess what I'm doing tomorrow!!

brianp38dse · Mar 29, 2020

kermit_rr said:
Yep dodgy connection somewhere. Put it back on the car and it worked for a few moments ie. Moved as i changed the temp on the car display, then stopped.
Progress i think, guess what I'm doing tomorrow!!

isolating

Grrrrrr · Mar 29, 2020

kermit_rr said:
Yes i see the value change but can't see if it goes all the way to zero or not as going thru the menus is too slow.
I did take the lid off the motor while still plugged in and turned the pot by hand, it went from 0-92 without any apparent dodgy readings in between

0 - 92 sounds odd. Never really played with that module but I would expect 0 - 256 for bits or maybe degrees movement.

kermit_rr · Mar 29, 2020

Grrrrrr said:
0 - 92 sounds odd. Never really played with that module but I would expect 0 - 256 for bits or maybe degrees movement.

I might be wrong but i think it's a percentage, 0 being fully closed, 100 fully open

romanrob · Mar 29, 2020

kermit_rr said:
The replacement pot i put in had different alignment so the arrows don't line up, it's 90° out so i took that into consideration when i put it all back together

So, does "taking into consideration mean you realigned the arrows, or left them 90 degrees out? they shd be realigned, obv. Or maybe try installing a different pot, since you're back in there. I think, when fitted, mine are showing between 1 and 9k across the wiper and one or other of the reference wires.

Bear in mind that if you have a service book symbol then all bets are off re the motors - HEVAC may try and protect them (eg my RH blend motor feedback problem allowed the LH blend to be controlled by HEVAC, but the distribution motor would not move) are there any gremlins elsewhere?

Grrrrrr · Mar 29, 2020

kermit_rr said:
I might be wrong but i think it's a percentage, 0 being fully closed, 100 fully open

Moght be right there. Rings a vague bell from when Gorsky was checking his.

romanrob · Mar 29, 2020

kermit_rr said:
I might be wrong but i think it's a percentage, 0 being fully closed, 100 fully open

Yes, it is, albeit that on one of mine the blend doors gets to 105

Datatek · Mar 30, 2020

kermit_rr said:
I might be wrong but i think it's a percentage, 0 being fully closed, 100 fully open

From memory it's a percentage, certainly it goes from near zero to 100

wammers · Mar 30, 2020

In practice the pot will never reach it's full travel in either direction. The flap stops will prevent that. Calibration gives the ECU a null point to work from. That is the reason for the arrow marks, they place the pot at mid point initially.

kermit_rr · Mar 30, 2020

To find the mid point, i found the max value and divided in half, then set the pot to that value, then put the output drive on with the flat parallel to the side of the case as normal
I do think it's a cable/connector problem somewhere given it now seems to work intermittently

Datatek · Mar 30, 2020

kermit_rr said:
To find the mid point, i found the max value and divided in half, then set the pot to that value, then put the output drive on with the flat parallel to the side of the case as normal
I do think it's a cable/connector problem somewhere given it now seems to work intermittently

Depending on the potentiometer you used you cannot find the mid point like that, some pots operating on a logarithmic scale, you find the mid point mechanically.

kermit_rr · Mar 30, 2020

Datatek said:
Depending on the potentiometer you used you cannot find the mid point like that, some pots operating on a logarithmic scale, you find the mid point mechanically.

did not know that! it does seem to be a normal scale, just 90 degrees out.. the physical mid point reads around 5K ohms so it must be right?! *must*

Datatek · Mar 30, 2020

kermit_rr said:
did not know that! it does seem to be a normal scale, just 90 degrees out.. the physical mid point reads around 5K ohms so it must be right?! *must*

Fair enough, you have a linear scale pot which is correct. I would still use the mechanical mid point though.

romanrob · Mar 30, 2020

Kermit - you say cable/ connector problem... fyi I cleared my "RH Blender motor feedback faulty" error by replacing one pin (on the LH motor !!) and the entire connector block - so the solution can be in a non-obvious place. Also POs may have spliced/ repinned the connector, so worth running over all the wiring on the blend motor connector IMHO

kermit_rr · Mar 30, 2020

cheers, yes, the PO had cut the cable and replaced/repaired the motor that way, i've redone the connections but need to check the whole thing

P38A blend motor

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