71bmr02

id the relay

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I was hoping to find a delay relay for the wipers to upgrade my system and came across this  on a wiring harness i have.  No numbers on it, all worn off likely from being in storage.  This doesnt appear to be the wiper delay relay, what is it?

 

Thanks

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Not 100% sure, but that looks like the little box from a late model that tracked engine run time and would then light up the EGR and Reactor Service lights on the center dash pod.

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The EGR check lights where activated mechanically off the speedo cable. If I remember, that looks like the relay for the magnetic vacuum switches off the smogged 02's.  I have been known to not remember everything correctly...:)

Matt

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On 3/23/2018 at 10:13 AM, Schnellvintage said:

The EGR check lights where activated mechanically off the speedo cable. If I remember, that looks like the relay for the magnetic vacuum switches off the smogged 02's.  I have been known to not remember everything correctly...:)

Matt

 

+1

 

I agree with Matt.  It’s a good ol' Drehzahlschalter (an engine speed relay), and it controls the magnetic vacuum switches on 1974 and later 2002’s.  It is part of the U.S. emissions system.  It is not found on tii’s, which have a similar looking, but different, Zeitschalter (a timed cold start relay).

 

Please don’t ask me any questions about how and when it works, as the above statement totally exhausted my knowledge of it...🙁

 

The last two photos show one in captivity, on my ‘76 in August 1983 and in February 2013.

 

Regards,

 

Steve

 

 

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Edited by Conserv

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Definitely not a wiper relay-all the ones I've seen have black plastic cases, and live under the dash, near the turn signal relay and the hood release latch.

 

The seven terminal wiper relay with the intermittent setting feature you seek will be found on '76 2002s, some '75s and all E21 320's.  On the '02s, look for a wiper lever that has three markings on the knob--a dashed line for intermittent, a single line for low speed and two lines for high speed.  

 

If you have a squarelight car, it'll be pre-wired for the intermittent feature; you just need the relay and the proper steering column wiper lever; if you have a roundie with a wiper relay, you'll need the proper dash switch that governs wiper speed (three positions vs two) and a wiring harness (pm me if you'd like the wiring diagram). The wiper switch on the stalk remains the same.  If you have an early roundie with no relay, you're better off finding a Hella universal intermittent relay kit.  

 

cheers

mike

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Thanks all.  consensus seems to be it's an engine speed control relay which makes it almost useless except as a wall hanger an I'm not so sure i'd want to take up that much wall space.   Unless someone wants to kick in another shot at this, we'll save the forum brainpower for something more important.

 

Thanks again

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"Drehzahlschalter" translates as "Speed Switch"... perhaps the Change Over Relay?  Sounds like a kick-down switch as you would find on an automatic tranny car.

 

 

image.thumb.png.686eccda7d02091499fbc32ed81a1737.png

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2 hours ago, Swiss 2002Tii said:

"Drehzahlschalter" translates as "Speed Switch"... perhaps the Change Over Relay?  Sounds like a kick-down switch as you would find on an automatic tranny car.

 

 

image.thumb.png.686eccda7d02091499fbc32ed81a1737.png

 

I suspect this is not a wiring diagram for 1974 through 1976 U.S.-spec cars, with full U.S. emissions controls.  I’m not absolutely certain one exists that includes the emissions system.  And I believe that 1974 through 1976 U.S.-spec cars are themselves not identical from an emissions control perspective, since all 1975 and California-only 1976 examples had thermal reactors.

 

The Drehzahlschalter is part of the emissions controls, which is what the electromagnetic vacuum valves also serve.  And it appeared originally on all 1974 through 1976 U.S.-spec 2002’s (not on 1974 tii’s). My ‘76, for instance, has a manual transmission, and was manufactured with a manual transmission.  I’ve shown photos above of the original Drehzahlschalter on my ‘76.  If you ditched the emissions system, you generally ditched this!

 

Just to be clear, I wasn’t speculating in my prior post that this might be part of the emissions system, after 42 years with my ‘76 — which retains  its fully-operational emissions controls — I am quite confident I know what a Drehzahlschalter relates to; I just don’t know when and how it “does its thing,” but it revolves around engine speed.

 

Regards,

 

Steve

 

Edited by Conserv

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Great info Steve.  Now I know a little more than I did a few minutes ago! Always learning! :)

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Yep...it's the speed relay. 

The only function of this relay is to provide  +12V  to the WHITE electro-magnetic vacuum valve on the bulkhead.

This happens when the engine speed is 1650 +/- 50 rpm.  The +12V closes the WHITE valve, thus shutting off vacuum to the DASH POT, which  extends the rod to crack open the throttle.

This is useful when decelerating (throttle closed, high rpm) to reduce vacuum and high pressure in the engine (think blow-by from the valve cover).

If you don't have/use the Dash Pot, then toss the White valve and Speed Relay into the neighbor's pool.

 

5ab89364acfcc_BMWSpeedRelay.thumb.jpg.bf39e8d1635aabbcefa585092d8cfea3.jpg

 

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4 hours ago, John76 said:

Yep...it's the speed relay. 

The only function of this relay is to provide  +12V  to the WHITE electro-magnetic vacuum valve on the bulkhead.

This happens when the engine speed is 1650 +/- 50 rpm.  The +12V closes the WHITE valve, thus shutting off vacuum to the DASH POT, which  extends the rod to crack open the throttle.

This is useful when decelerating (throttle closed, high rpm) to reduce vacuum and high pressure in the engine (think blow-by from the valve cover).

If you don't have/use the Dash Pot, then toss the White valve and Speed Relay into the neighbor's pool.

 

5ab89364acfcc_BMWSpeedRelay.thumb.jpg.bf39e8d1635aabbcefa585092d8cfea3.jpg

 

 

Thanks, John.

 

Very good to know, finally.... 😗

 

Love the illustration!

 

Best regards,

 

Steve

 

Edited by Conserv

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