Author Topic: Temperature Switches  (Read 953 times)

TEJOLX47

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Temperature Switches
« on: June 29, 2018, 09:57:42 »
Hi,

Can anyone tell me how the temperature switches (17ºC and 100º) work?
Bottom line questions are:
1. For 17ºC switch, is current sent if temp is greater or smaller than 17ºC?
2. For the 100ºC switch, is current sent if temp is greater or smaller than 100ºC?
My expectaction - that could be wrong - is that each switch would only send current when the abnormal situation applies, i.e., temp bellow 17ºC (engine tto cold) or above 100ºC (engine too hot).
Many thanks in advance.
Cheers
Francisco
Francisco

1970 280 SL (US delivered, Auto, AC, PS)
181 Light beige with 423 Tobbaco brown top

Peter van Es

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Re: Temperature Switches
« Reply #1 on: June 29, 2018, 13:31:15 »
You'll find all details here: https://www.sl113.org/wiki/Restricted/Engine-starting-aid-tour

You will need to become a full member before you get access. If you sign up now, you'll have access immediately after payment.
1970 280SL. Please do not mail or PM me questions on Pagoda's... I'm not likely to know the answer.  Please post on the forum instead!

TEJOLX47

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Re: Temperature Switches
« Reply #2 on: June 30, 2018, 19:30:38 »
Thanks Peter.
I have read most of these documents, but - not being an expert - I am still trying to put all together.
Eventually I will get there.
Regards
Francisco

1970 280 SL (US delivered, Auto, AC, PS)
181 Light beige with 423 Tobbaco brown top

Benz Dr.

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Re: Temperature Switches
« Reply #3 on: June 30, 2018, 20:48:21 »
The switch on the block goes to ground when the temperature is under 17 C and this will advance the ignition timing about 20 degrees to help with warm up. At 100 C the switch on the thermostat housing will go to ground and this will also advance the ignition 20 degrees to help with cooling down a very hot engine.

The problem with running ignition timing ATDC at idle is that it will make the engine run hotter than it would if set BTDC. The main problem, as I see it, is 100 C is already too hot and any timing advance probably won't work to cool your engine off once you're at 100 C or more. If a switch could be found that would close at 90 or 95 C then it would likely work much better. All of this is dependent upon the vacuum switch over valve working which is wired as a different circuit with the speed relays. If none of this stuff is working you are stuck with poorer warm ups after starting, a loss of 20 degrees of vacuum advance for your ignition timing ( which means poor performance and a thirsty engine ) and no vacuum advance once running too hot.

At that point, either you have to fix it so that everything works, or remove it all and go to the earlier 051 ignition system found on late 230SL's, 250SL, and early 280SL's. You would need a coil, distributor, and throttle body from an earlier engine.   
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

TEJOLX47

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Re: Temperature Switches
« Reply #4 on: July 09, 2018, 17:01:16 »
Many thanks.
That's the logic I missed to understand the way the emission control system works.
Cheers
Francisco
Francisco

1970 280 SL (US delivered, Auto, AC, PS)
181 Light beige with 423 Tobbaco brown top