Temperature Sensor?

[KUMARB]

(1) What is the purpose of a temperature sensor mounted on the thermostat housing of a 1971 280SL? Is it connected to the temperature gauge in the instrument cluster? Please forgive my ignorance.

(2) Also, would you know if there is any unused threaded taping on the engine for me to install a temperature switch? I would like to connect the temperature switch to operate the auxiliary fan to keep the engine from overheating. Any suggestions?

Regards,

[Jonny B]

The topic about the wire at the top of the thermostat housing has been raised before. I tried a search on "thermostat" and got one relevant hit, but there was not any detail. You might want to try some other combinations to see if you can find anything more. The search tool is a good one, there is a lot of information on the site.

[jeffc280sl]

The temperature switch on top the thermostat is known as the 100 degree C or 212 degree F switch.  On the later USA versions this switch is part of the emissions system. When the temperature exceeds 212 this switch activates the two way valve and ignition timing advances.  This causes the idle speed to increase and I imagine fuel is burned more completely and emissions are reduced.  You can use this switch to turn on an aux fan although the temperature is a liitle high.  I suggest you consider a separate adjustable thermostat from the after market.  Weather is getting better so the overheating issue will become active again.  You may want to consider a heater hose bypass.  Search on the topic for details.

[KUMARB]

Thanks, JeffC and Jonny, for your advice. It was very helpful.

The whole emission control system has been very confusing to me. I looked into the MB Service Manual, and it shows emission control system for a carburetted engine and nothing for injected engine, and fails to note that they are different. Compounding the confusion is my own car where emission control has been tampered with by the previous owner. The vacuum lines to the two-way valve are disconnected, relays and their mounting bases missing. I am trying to figure them out to be able to restore my car to its original working condition.

I have two vacuum ports on the intake manifold. One of them should be connected to the two-way valve. The other one, I assume, is a test port, which needs to be kept capped. Is that correct?

Regards,