924 Early 944 Late 944
In degrees Centigrade. Data from Porsche 944 Service Manual section 90. Data in red is extrapolated from BOSCH sender curves.
PROCEDURE - Water Temperature Gauge Sender.
Calibration Check, Early 944
Connector is in engine compartment above the master cylinder. Pin side
of
the connector shown.
( o o o
( o o x
( o o o
X - blue wire with yellow stripe. Water Temperature Gauge Sender.
Practice Calibration Check:
With the engine at room temperature, disconnect connector and measure between ground and the sender pin (marked with an x). The reading should be in the 400 to 600 ohm range. This is just a ballpark figure. If you are outside this value you may have a problem.
Calibration Check:
Now for the real test. Reconnect connector. Start engine. Run engine
until the temperature reaches the far-left mark on the gauge. This is the 40-degree C
mark. Turn off engine. Turn ignition on but do not start the car. Verify that the gauge is
stable on the first mark. If you over-shot the mark, sit there until it cools.
With the temperature stable on the first mark on the gauge, pull the connector again and
measure the sender resistance. It should be 287 ohms. If you are a little off +-30ohms,
that is fine. If the resistance value reads low, the gauge will read on the high side.
The water temperature gauge sender in my 944 read over 1000 ohms. Failed badly. The one I
pulled from the 924Turbo read 394. Another failure. Bought a new sender. At 40 degrees, it
reads 250 ohms (287 ohms is nominal). I am a little low but acceptable. My gauge will read
a little high.
NOTE: Early 944s use a copper wire and copper connector to
attach to the sender. This wire will form a green oxide and it can cause the
gauge to jump erratically. Cut off the connector and strip and clean the wire.
Crimp on a new connector. This will help steady your gauge
readings. The early 944 uses a single wire to connect to the sender and the return path is
by engine ground. Grounding problems often result in erratic gauge behavior.
Also: This is a calibration check and no actual calibration is performed. That requires the turning of screw drivers and the like.
