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What does this do?

Posted: Mon 11 Jun, 2018 9:14 am
by cpg003
Morning all,

Can anyone give me some clarification of what this is and what it does? It’s mounted underneath the coolant reservoir of my C107 and has two vacuum lines and an electrical connection attached. Thanks in advance.

Ignore the writing on this one, just a pic I found on eBay.
Pierburg Vientil pressure regulator DB2097 ZK 12982 8171

Re: What does this do?

Posted: Mon 11 Jun, 2018 6:49 pm
by John Green
Idle speed adjustment when the A/C compressor cuts in. It interrupts the vacuum to the ignition distributor.

Re: What does this do?

Posted: Mon 11 Jun, 2018 7:57 pm
by cpg003
Thanks John. Much appreciated.

Re: What does this do?

Posted: Wed 04 Jul, 2018 8:28 pm
by Chai
Those with too much time on their hands can clean the very fine metal mesh that acts as an air filter in that part. The filter is located at the top of the unit (yellow looking item in the photo).

The filter in my 40-ish year old unit was partially clogged with dust. The tip of a needle can be used to poke out the debris (I did say ... too much time in my hands).

The air-leak to the vacuum line connected to the distributor when the air-conditioner is switched results in the cancellation of the distributor retard (i.e ignition is advanced and engine revs up).