Mystery switch in the battery tray???

I'm still going over my 'new' 96 Sport, and today noticed an unusual switch in the battery tray. It's a pressure switch, and activates/deactivates when the battery is removed. It has a two-wire connector that goes into a nearby wiring harness. Anyone know what this switch operates?
Thanks,
ROE

Ambient temp sensor. That is the sensor that is used to determine ambient temp. Apparently that spot gives a good approximation of ambient.

Thanks for the reply, Explorer. Are you sure it's for ambient temp, and not the battery temp? This thing looks like it's spring loaded, and compresses when the battery is placed on it......

Well technically, yes, it measures battery temp being that it is in direct contact with the battery case. I'm calling on my long term memory here, but I remember being told in DC training that it was one variable the PCM uses to determine ambient conditions. It is obviously affected by engine compartment heat and so if the engine has been run recently, isn't truely an ambient sensor, but gives a good idea of the state of the engine as far as warmup is concerned. I just looked in my manuals and it doesn't actually state anything other than that its for measuring batt. temp. It's just what I recall from my training.

Runnin'OnEmpty said:

Anyone know what this switch operates?
Thanks,
ROE

Click to expand...

Sounds like a bomb trigger to me. The previous owner must have hated their mechanic at some point.

It is used by the PCM to vary alternator output. The lower the temperature, the higher the output and vice versa. This is copied directly from the '00 FSM: "The BTS is also used for OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled, depending upon BTS input (for example, disable purge and enable Leak Detection Pump (LDP) and O2 sensor heater tests). Most OBD II monitors are disabled below 20°F." This last part is why, if the battery doesn't get up to a certain temp., it can cause the AW4 not to go into overdrive (but it's been below 0* here and that's never happened to me).

OK, thanks guys.
Mystery solved!
:repair:

Runnin'OnEmpty said:

OK, thanks guys.
Mystery solved!
:repair:

Click to expand...

Was it Old Man Jenkins or Red Herring?