thermo-time switch

[doug]

In the 'Bentley', the chart on page 25 that shows resistance values for the 35degC/8sec thermo-time switch at various temperatures.

• @ 30degC and below, terminal G to ground: 25-40ohms; terminal W to ground, 0ohms.

• @ 40degC and above, terminal G to ground: 50-80ohms; terminal W to ground, infinite ohms.

I was testing the switch on my 528e trying to diagnose a no-start condition when warm. I found that when cold, the switch meets the test criteria, but when the switch is warm, the 'G' terminal shows 75 ohms to ground, and the 'W' terminal shows 150 ohms to ground. Thought I'd swap the switch from my 635. I tested it and got the same results. Is the Bentley wrong, or is this the typical manner in which the TTS fails?

[a]

IVe tested it with a test light, but I forget the particulars. Any way, the light goes out after ~ 8 seconds or so, so I figured the TTS is OK.

[doug]

still trying to verify resistance values...

[doug]

Can somebody measure resistance between each of the two connectors on their TTS and the TTS case (or some other ground) when the car is warm and report back? Thanks.
One should measure 70-80 ohms. The other should be open (according to Bentley), but both of mine measure ~150 ohms. Thanks.

[BAVARIANUT]

It only influences fuel for the first 30 seconds of startup in cold weather. I have one that I just bought off of Haygood a few weeks back. My motor is now shot, so you can have it cheap. Its for an 86 535i. the fuel injection coolant temp sensor is just as old, but never installed.

[doug]

Can somebody measure resistance between each of the two connectors on their TTS and the TTS case (or some other ground) when the car is warm and report back? Thanks.
One should measure 70-80 ohms. The other should be open (according to Bentley), but both of mine measure ~150 ohms. Thanks.

I just tested another TTS in a friends 535i and got the same results as before. Current score is ...

me: 3
Bentley:0

Any nice bored people out there with a multimeter and a warm m20 or m30? Just takes a minute to measure. Pull the connector off (depress the wire keeper and pull) and measure between each of the terminals and the TTS case. One should show around 75 ohms, the other should show open circuit (according to Bentley) or about 150 ohms (based on the three I have measured so far). The TTS is the largest of the three or four devices mounted in the thermostat housing.

[doug]

Any nice bored people out there with a multimeter and a warm m20 or m30? Just takes a minute to measure. Pull the connector off (depress the wire keeper and pull) and measure between each of the terminals and the TTS case. One should show around 75 ohms, the other should show open circuit (according to Bentley) or about 150 ohms (based on the three I have measured so far). The TTS is the largest of the three or four devices mounted in the thermostat housing.

Pretty please?

[doug]

Any nice bored people out there with a multimeter and a warm m20 or m30? Just takes a minute to measure. Pull the connector off (depress the wire keeper and pull) and measure between each of the terminals and the TTS case. One should show around 75 ohms, the other should show open circuit (according to Bentley) or about 150 ohms (based on the three I have measured so far). The TTS is the largest of the three or four devices mounted in the thermostat housing.

Pretty please?

Ummm ... with sugar on top?

[eddycooper]

I have two switches that agree with your measurements.

Eddy

[doug]

I have two switches that agree with your measurements.

Eddy

Thanks. It does pay to be patient. 8)