1979-1993 & 94 Conv [Subscribe to Daily Digest] |
 | [Main C900 Bulletin Board | BBFAQ |
Prev by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: '90 heated seats in an '86, how do I wire them up? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 15 Oct 2003 12:32:55
In Reply to: '90 heated seats in an '86, how do I wire them up?, steve, Tue, 14 Oct 2003 10:18:29 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As Irie says, the '86 has a simple temperature switch built into the seat pad, in series with the heater coil. When the seat gets above a temp (I think it's around 88 F), the switch opens, and cuts off power to the heater coil. When the seat temp drops below a temp (can't remember exactly what), the switch closes. Power is applied whenever the ignition is on. There is a ground wire to chassis, and a power wire to 12 volts.
The controller is different - there are three wires. There is one ground wire to chassis, that connects to the heater coil and a temperature sensor. The other side of the heater coil and the temp sensor both run to the controller (two wires).
The temperature sensor is a NTC device - it's a resistor with a Negative Temperature Coefficient - namely, the resistance drops when the device gets warm. In the controller is a little circuit and a relay. The knob on the front of the unit has four settings - off, and 1, 2, and 3. Off, is, well, off. 1, 2, and 3 correspond to sucessively warmer temperatures. If the seat temperature sensor says the seat is colder than the temperature setting on the switch, the relay closes, and provides 12 volts to the heater coil. When the seat warms up above the selected set point, the relay opens. Hotter settings correspond to lower temperature sensor resistances.
The controller measures the resistance by using the sensor as the lower leg in a voltage divider - the warmer the seat, the lower the voltage.
OK, so how to you make this work? You need to connect up the controller-
Pin 7 - dash illumination - this is the bulb in the controller
Pin 9 - ground
Pin 2 - 12 volts. I'd take this from the seat heater fuse
Pin 10 - tie to the 'high' side of the seat heater element
Pin 6 - sensor in the seat.
The other side of the sensor should be tied to ground. OK, there is no sensor in the seat of an '86. What do you do?
Two options - the best is to get a seat heater pad from a 90 or later. This has the proper sensor. They aren't that expensive.
Option two - wire in your own sensor. Unfortunately, I don't know the complete specs on the sensor. All I know is that it's a NTC thermistor, with a value of around 1K ohms at room temperature (typically 25 degrees C, or 77 F). I don't know the temperature coefficient (how much the resistance would change with temperature).
Finding a sensor out of a later model heated seat would be best. The same system was used on the 9000 in all years, so grabbing a sensor out of a 9000 seat would work. I don't know if a 9000 seat heater pad will fit in a 900 seat.
posted by 192.249....
, Wed, 15 Oct 2003 12:32:55 <-- Viewing This Message
, Tue, 14 Oct 2003 10:40:05
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
