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Old 08-16-2003, 01:09 PM
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JimF JimF is offline
'94 S500: only 793 sold!
 
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,925
I'm not sure we all are. . .

straight!

The CTS is the B10/8 sensor; that's what I call it; the ECT is B11/2. Check the picture on my page under MENU#18; clearly shows both sensors.

The ECT sensor (B11/2) temperature vs resistance readings are:
Temp(C)--Temp(F)-------- Ohms
20 --------- 68 ----------- 2500
30 --------- 86 ----------- 1700
40 ---------104 ----------- 1170
50 ---------122 ------------ 830
60 ---------140 ------------ 600
70 ---------158 ------------ 435
80 ---------176 ------------ 325
90 ---------194 ------------ 245
100 ------- 212 ------------ 185

The reistance of this sensor should be within +/-5%. Again this is the ECT sensor.

The CTS (B10/8) sensor's temp vs resistance characteristics are different from the B11/2 sensor. But the key values for this sensor's resistance is the resistance value at 100C, 107C and 115C.

For 100C, the resistance sb 310 ohms;
For 107C, the resistance sb 250 ohms;
For 115C, the resistance sb 200 ohms.

At these resistance settings, the fans should come on at low speed (310 ohms); second speed (250 ohms) and high speed (200 ohms).

For your '93 500SEL (W140): If your CTS sensor (B10/8) reads 183 ohms at 80C, it is BAD! Also if your ECT sensor (B11/2) reads 183 ohms at 80C, it's bad also.

This assumes it was read correctly. Hard to see why it's that low: normal failure mode for this device (varistor) is going to HIGH resistance.
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Regards . . . . JimF
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'94 S500 Cpe

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