A/C Hot when lever is off the full cold - one more user stumped
03-01-2013, 10:20 AM
#16
Drifting
If it's as high as 5320 at the hot end then it will be driving the motor towards full hot.
Why has the sensor string resistance suddenly jumped up? Did you measure the internal sensor correctly as I suspect it has drifted high out of spec which would explain the string resistance out of range at high end.
03-01-2013, 08:25 PM
#18
Rennlist Member
Thread Starter
StratfordShark,
I noticed the difference too. I am thinking that part of the story is that it got much colder in FL these last two days, so I will retest tomorrow to make sure. Thanks for following this and helping.
Tails,
Yes, I went through Wally's write up a few times. Is there anything you are thinking that I am missing? Any feedback is welcome, as I am really struggling here.
Thanks
I noticed the difference too. I am thinking that part of the story is that it got much colder in FL these last two days, so I will retest tomorrow to make sure. Thanks for following this and helping.
Tails,
Yes, I went through Wally's write up a few times. Is there anything you are thinking that I am missing? Any feedback is welcome, as I am really struggling here.
Thanks
03-01-2013, 09:05 PM
#19
Electron Wrangler
Lifetime Rennlist
Member
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Update - still stumped!
Took my time and retested tonight:
1. Sensor String - between Setting motor pins 4 and 12: 6,240 and 5,320 Ohms. Delta ~ 1,000 Ohms - OK
2. Continuity of the various parts of sensors circuit: all OK (between Setting Motor pin 12 and Head pin 13: 0 Ohm; Head pin 14 and T31 pin 1: 0 Ohm; T31 pin 2 and T29 pin 4: 0.03 Ohm; Setting Motor pin 4 T29 pin 3: 0.04 Ohm)
3. Outside sensor: between pins 3 and 4 of T29: 508 Ohms OK
4. Sensor String including the Setting Motor - between T29 between pins 3 and 4 car side: 6,990 and 6,020 Ohms, delta ~ 1,000 Ohms. The delta is OK, not sure about the individual numbers.
5. Sensor String: between Head pin 14 (car side) and Setting Motor pin 4: 2,910 Ohms. Also none is grounded / shorted
6. Checked for ground or power on all pins of Setting Motor connector and Head connector : all OK
So, it seems I am good with all these.
The suspect then becomes the Setting Motor, since when we check test 1 above, it excludes it. Maybe someone can tell me if test 4 above indicates something too high / too low as it includes the setting motor on that measurement.
I opened up the Setting Motor and cleaned the contacts using a electric degreaser and cotton swabs. The board appeared fine, but got some gunk from the transistors solders. I am pretty clueless to try to resolder or test the things inside.
I have not reassembled the Setting Motor back...it is getting pretty late.
Any suggestions?
Thanks
Took my time and retested tonight:
1. Sensor String - between Setting motor pins 4 and 12: 6,240 and 5,320 Ohms. Delta ~ 1,000 Ohms - OK
2. Continuity of the various parts of sensors circuit: all OK (between Setting Motor pin 12 and Head pin 13: 0 Ohm; Head pin 14 and T31 pin 1: 0 Ohm; T31 pin 2 and T29 pin 4: 0.03 Ohm; Setting Motor pin 4 T29 pin 3: 0.04 Ohm)
3. Outside sensor: between pins 3 and 4 of T29: 508 Ohms OK
4. Sensor String including the Setting Motor - between T29 between pins 3 and 4 car side: 6,990 and 6,020 Ohms, delta ~ 1,000 Ohms. The delta is OK, not sure about the individual numbers.
5. Sensor String: between Head pin 14 (car side) and Setting Motor pin 4: 2,910 Ohms. Also none is grounded / shorted
6. Checked for ground or power on all pins of Setting Motor connector and Head connector : all OK
So, it seems I am good with all these.
The suspect then becomes the Setting Motor, since when we check test 1 above, it excludes it. Maybe someone can tell me if test 4 above indicates something too high / too low as it includes the setting motor on that measurement.
I opened up the Setting Motor and cleaned the contacts using a electric degreaser and cotton swabs. The board appeared fine, but got some gunk from the transistors solders. I am pretty clueless to try to resolder or test the things inside.
I have not reassembled the Setting Motor back...it is getting pretty late.
Any suggestions?
Thanks
The whole loop is out of spec - you are always above the max spec value. I keep telling you its the loop - please listen.
Alan
03-02-2013, 04:55 PM
#20
Rennlist Member
Thread Starter
Thanks for the help guys.
I found that when I checked resistance at the Setting Motor between terminals 4 and 12 with the slider at 65F I found anything between 3,800 Ohms to 6,000+ Ohms. And with the slider at 85F anything between 4,770 and 6,410 Ohms.
So it goes from acceptable to too high.
Then I left the multimeter connected and started moving the components. I found that when I pushed, pulled or twisted the wires a bit at the Head 15 pin Connector, the change in resistance happened. However it seemed that it was no wire in particular as this happened with almost all of them. At a times tapping at the Head would also cause some changes.
Interestingly enough, when testing the Head according to the WSM (pages 87-110 thru 87-112) it passed all 20 or so tests. So, it really does not look like it is the Head or its connector.
And except for the issue mentioned above, all WQSM tests were OK, indicating a good Setting Motor as well.
And the continuity and short tests on all sensor loop wires were fine too.
Now, how do I identify where the problem is?
The Head 15 pin connector is connecting tightly to the Head Unit (no wiggling). But allows for some movement.
I am almost thinking about using a soldering iron and re-heat some of the solders insider the Head, but again, it passed all tests of the WSM and I am totally clueless about anything inside. I already carefully cleaned the board (before all this, so it was not that).
The other option would be to replace the 15-pin Connector at the Head. It will be certainly cheaper than replacing the Head and maybe that is the problem. But how do I replace that? What kind of tools are needed to replace that connector?
Or maybe borrow a Head Units from soemone in South Florida who would be willing to lend me one to try it?
EDITED: added the resistenace change is happening with the slider in either 65F or 85F
Thanks
I found that when I checked resistance at the Setting Motor between terminals 4 and 12 with the slider at 65F I found anything between 3,800 Ohms to 6,000+ Ohms. And with the slider at 85F anything between 4,770 and 6,410 Ohms.
So it goes from acceptable to too high.
Then I left the multimeter connected and started moving the components. I found that when I pushed, pulled or twisted the wires a bit at the Head 15 pin Connector, the change in resistance happened. However it seemed that it was no wire in particular as this happened with almost all of them. At a times tapping at the Head would also cause some changes.
Interestingly enough, when testing the Head according to the WSM (pages 87-110 thru 87-112) it passed all 20 or so tests. So, it really does not look like it is the Head or its connector.
And except for the issue mentioned above, all WQSM tests were OK, indicating a good Setting Motor as well.
And the continuity and short tests on all sensor loop wires were fine too.
Now, how do I identify where the problem is?
The Head 15 pin connector is connecting tightly to the Head Unit (no wiggling). But allows for some movement.
I am almost thinking about using a soldering iron and re-heat some of the solders insider the Head, but again, it passed all tests of the WSM and I am totally clueless about anything inside. I already carefully cleaned the board (before all this, so it was not that).
The other option would be to replace the 15-pin Connector at the Head. It will be certainly cheaper than replacing the Head and maybe that is the problem. But how do I replace that? What kind of tools are needed to replace that connector?
Or maybe borrow a Head Units from soemone in South Florida who would be willing to lend me one to try it?
EDITED: added the resistenace change is happening with the slider in either 65F or 85F
Thanks
03-03-2013, 11:44 PM
#24
Rennlist Member
Thread Starter
Updae - fixed
Fixed. 
Well, at least for now!
I replaced the multimeter battery as per Alan's recommendation and unfortunatelly the problem remained.
I disassembled the AC Head Unit again and noticed that without the plastic housing, as I twisted it a bit , the resistances would go from spec to high, which was driving the Setting Motor to go to the Hot position.
I then noticed that if I had the internal cirtcuit board pressed against one of the places where the screws bite, the problem would go away.
Then I reassembled and put an extra torque to the screws. Tested everything and it is working.
This might be a temporary solution, but I will take it.
For those facing a similar problem I would say to retorque the screws at the Head and retest.
Thanks to all of you for the help
Well, at least for now!I replaced the multimeter battery as per Alan's recommendation and unfortunatelly the problem remained.
I disassembled the AC Head Unit again and noticed that without the plastic housing, as I twisted it a bit , the resistances would go from spec to high, which was driving the Setting Motor to go to the Hot position.
I then noticed that if I had the internal cirtcuit board pressed against one of the places where the screws bite, the problem would go away.
Then I reassembled and put an extra torque to the screws. Tested everything and it is working.
This might be a temporary solution, but I will take it.
For those facing a similar problem I would say to retorque the screws at the Head and retest.
Thanks to all of you for the help
