Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

About cabin temperature sensor

 
Old 11-01-2012, 07:21 PM
  #16  
Charley B
Addict
Rennlist Member
 
Charley B's Avatar
 
Join Date: Apr 2006
Location: Patterson, Ca
Posts: 4,372
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Alan View Post
If the max heating switch is always closed - you will get roasted (but you can set fan to 0 and open the windows. Alan
And close the vents.
Charley B is offline  
Old 11-02-2012, 10:48 PM
  #17  
FiveElements
User
 
FiveElements's Avatar
 
Join Date: Oct 2012
Location: San Ramon, Calif.
Posts: 382
Likes: 0
Received 0 Likes on 0 Posts
Default

If it matters, I'm 44 years old, have an 89 car and my degree in electronics with honors. I've only owned 928 cars for 15+ years including an 85, 87 and 89 now. I know I can fix this simple heater issue. I just need to know what the resistance is for each temperature on the sensors. The heater does go to cold when I put the temp lever full over to 65║ so part of the system is working. I'll look over this chart and start checking. So far, the outside temp sensor is reading 380ohms at about 75║F. If anyone knows the ratings for the inside temp sensor, I can check that next. The center console comes out very easy. I don't mind pulling it out and have already. I checked the wires and fan for the inside temp sensor and all look secure. The mini-fan behind the temp sensor is also spinning. At least, I hear it spinning. This problem did not happen suddenly. It started as an intermittent problem. One day it would work fine and the next day the heater stayed on full intensity. Now the problem is always happening, so whatever is wrong is consistent. Any suggestions?
FiveElements is offline  
Old 11-02-2012, 11:50 PM
  #18  
Calgary Ole
User
 
Calgary Ole's Avatar
 
Join Date: Feb 2009
Location: Calgary Canada
Posts: 909
Likes: 0
Received 0 Likes on 0 Posts
Default

Check that the setting motor works first. They do fail and get stuck in one position.

Here is a picture

Last edited by Calgary Ole; 06-23-2014 at 10:50 AM.
Calgary Ole is offline  
Old 11-03-2012, 06:35 AM
  #19  
John Speake
Addict
Rennlist Member
 
John Speake's Avatar
 
Join Date: Feb 2002
Location: Cambridge England
Posts: 6,903
Likes: 0
Received 4 Likes on 4 Posts
Default

This is the info I have:
Inside Sensor

From Plug T31 4 Pin Console RHS Plug Pin 1 (YE)*
To Plug T29 4 Pin Console RHS Plug Pin 2 (YE)*

2570 Ohms at 20C (68F)
2220 Ohms at 25C (77F)
1900 Ohms at 30C (86F)

I found I could replace a faulty one with an easily obtained thermsitor with a fixed resistor in parallel.
John Speake is offline  
Old 11-06-2012, 08:31 PM
  #20  
PC-85-928S
User
 
PC-85-928S's Avatar
 
Join Date: Jul 2011
Location: Long Island, NY
Posts: 538
Likes: 0
Received 0 Likes on 0 Posts
Default

How does the plastic cabin grill separate from the sensor unit?
This is the plastic piece that always seems chipped
PC-85-928S is offline  
Old 11-06-2012, 09:14 PM
  #21  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,934
Likes: 0
Received 0 Likes on 0 Posts
Default

Only from behind - the reason they are chipped is because people don't know this...

Alan
Alan is offline  
Old 01-29-2013, 08:30 PM
  #22  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

BUMP...

Quality thread/ info right here!
Tony is offline  
Old 01-29-2013, 11:08 PM
  #23  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by jcorenman View Post
..............

Here's a marked-up copy of the wiring for the sensor chain. The test-points are pins 4 & 12 on the setting-motor connector-2 (called "control unit" on the schematic, the control-head is called the "control switch" at the top).
so according to this, one should have continuity at all times (power on...power off) between the yellow wires leading into pins 12 and 14 (temp sensor loop)
Attached Images  
Tony is offline  
Old 01-29-2013, 11:19 PM
  #24  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,934
Likes: 0
Received 0 Likes on 0 Posts
Default

Well its 12 & 4 on the setting unit but yes the total loop should never be OC nor should it be SC to 31 or 30 (will be some resistance) and the total loop resistance should vary depending on temp & slider setting. The total loop resistance should be in the rages of ~3100 ohms - ~5100ohms -> with a ~1000 Ohm variation based on the slider position...

Alan
Alan is offline  
Old 01-29-2013, 11:32 PM
  #25  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Alan View Post
Well its 12 & 4 on the setting unit but yes the total loop should never be OC nor should it be SC to 31 or 30 (will be some resistance) and the total loop resistance should vary depending on temp & slider setting. The total loop resistance should be in the rages of ~3100 ohms - ~5100ohms -> with a ~1000 Ohm variation based on the slider position...

Alan
thats what i thought, time to pull the font wheel and liner.

IT never ends!!!

I wonder what a 26 yr old Aston Martin will be like?
Tony is offline  
Old 01-30-2013, 03:58 AM
  #26  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

OK...so this cant be right

I pulled the front fender liner to gain access to the OAT sensor wiring. The connection was solid. I unplugged it and then tested the wires.

One of the wires that leads to the mix/setting motor is showing ground when using the ground for the head light motor.

The other wire doesnt.

if i then go under the dash and unplug the connector from the setting motor, i no longer get the ground reading.

Is something internal to the setting motor bad? or am i missing something?

Tommorrow i will place a test lead on the ground connector on the seting motor plug to ground and then test the two contacts where the yellow sensor wires connect.


Just in case...how do you get this SOB out???
Attached Images  
Tony is offline  
Old 01-30-2013, 09:02 AM
  #27  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,934
Likes: 0
Received 0 Likes on 0 Posts
Default

Tony - The test is of just the loop not including the setting motor - so you cant test as you describe at the outside sensor. To do something like that that you'd have to unplug the setting motor and short pins 12 & 4 on the connector - then subtract the outside sensor resistance range from the expected vales.

Alan
Alan is offline  
Old 01-30-2013, 04:53 PM
  #28  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

Well, I'm 99.9% sure i do not have continuity along the circuit shown in RED. All the other ones check fine using the same process.

Setting motor plug pin 12 to control head plug pin 13....OK
Setting motor plug pin 4 to OAT sensor plug ................BAD
Inside temp sensor plug to control head plug pin 14......OK
Inside air temp plug to Outside airtemp plug................OK



Neither the setting motor or the control head are connected to their respective connectors. I am just checking continuity of the wiring.

The circuit in question shown in red.

The only place a physical connection takes place is at "T29" and since i already have a good test on a OAT sensor wire going through that connector already i would "assume" that every thing is connected.

Am i missing something obvious? Im just checking plug to plug
Attached Images  
Tony is offline  
Old 01-31-2013, 01:50 PM
  #29  
Tony
No wide loads, please!
Lifetime Rennlist
Member
 
Tony's Avatar
 
Join Date: May 2001
Location: Las Vegas
Posts: 13,130
Likes: 0
Received 0 Likes on 0 Posts
Default

Only thing worse than breaking your car is fixing it and really having NO idea how you fixed it.

All the circuits are now fine. The T29 connector is on the passenger side of the center console area...I pulled it apart there and had continuity back to the connector in the wheel well...the problem now was from T29 to the setting motor Pin 4 ...but where?

I had the pod out anyway so i pulled the end of the harness/connector that leads to the setting motor up and through the area near the ignition switch. It made it easier to get at. I checked continuity from the connector back to T-29...it checked ok WTF!!! ...so where is the problem??

Plugged T29 back together rechecked the whole circuit from the mix motor plug back to the temp sensor...checks OK!! Really scratching my head...but i will take it!

My guess is either a bad SINGLE pin connection at T29...sure didn't appear to be....OR...something was amuck in the 2ft run of harness from T29 to the setting motor that i fixed when pulling it up and out to test.

The circuit no longer shows ground from setting motor pin 4 to OAT pin 1 either !
Attached Images  
Tony is offline  
Old 01-31-2013, 03:08 PM
  #30  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,934
Likes: 0
Received 0 Likes on 0 Posts
Default

Hah! so it all works OK now? Or is it all apart...

Alan
Alan is offline  

Thread Tools
Search this Thread
Quick Reply: About cabin temperature sensor


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: