And close the vents.

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 65º 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 75ºF. 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?

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

Here is a picture

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.

How does the plastic cabin grill separate from the sensor unit?
This is the plastic piece that always seems chipped

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

Alan

BUMP...

Quality thread/ info right here!:thumbup:

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)

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

:soapbox: 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?

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???:banghead:

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

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

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!!! :soapbox::soapbox:...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!!:soapbox: 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 !:rockon:

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

Alan