Constant Speed Solenoid + CSV

[mdsalemi]

I know the CSS is activated to apply a bit of throttle to maintain idle speed when the car is in drive with the foot on the brake, or in the case of standard transmission cars, when the a/c is on.

Question: is this CSS tied in to temperature?  So that on a cold vehicle, idle speed is maintained a bit higher?

Second Question:  When starting from cold, for how long does the CSV stay activated?  Until it warms up, or just briefly until the engine starts?

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[George Davis]

Michael,

The CSV is only activated during cranking, and the total length of activation varies with temperature, from not at all (engine hot) to 12 seconds (engine very cold).  Time is controlled by the TTS.  The time is additive, so if the temp will allow for, say, 4 seconds of activation, then 2 cranks of 2 seconds each will use up the 4 seconds and it won't activate again until the TTS has cooled back down.

The above assumes the car does not have the 1 second relay.  If the 1 second relay is there, the CSV will always activate for at least 1 second during cranking, even if the TTS is timed or temperatured out.

Hope that helps.  Don't know about the CSS.



George Davis
'69 280 SL Euro manual

[Jonny B]

The CSS solenoid, the electric one on the intake runner, is activated by a pressure switch on the transmission. There are two small pressure switches one on each side that will activate the CSS when the tranny is in either reverse or drive. On the later cars (do not know the cutoff/start point), the solenoid is there, but is not even hooked up if there is no A/C. That is where the vacuum dashpot takes over (and all the discussion about the slip fit throttle rod, etc.)

Jonny B
1967 250SL Auto