"Dynamic oil pressure warning system" questions

[jackbombay]

So my 86 Quantum has the Dynamic oil pressure warning system, IT uses two sensors and RPM input to set off the buzzer. Below 7 PSI at Idlw and you get a light, below ~26 PSI above 2500 RPM and you get abzzer and a flashing light. The 2.0 Audi TD did not come with an alternator so I am using the one off the quantum, but it has no "W" terminal, so I have no RPM input for the Oil pressure warning system which means  (I think) that the car will always think it is Idling so the higher pressure switch will never "be in charge" of the warning.

   The tach in the car is for a 5 banger gasser, if I got a new alt for the Audi 5 banger Diesel with a "W" terminal would it's signal be correct for my existing tach? and what about for the Dynamic oil pressure warning system?

[Otis2]

Jack,

A diesel alternator with a W signal will not power the gasoline tach that you have in the car now.  

You'd have to hack either the output of the W signal, or the calibration of the gas tach, to make it work.  This company sells a gadget that converts the W signal into something that a gas tach can recognize:  http://www.dakotadigital.com/Detail.cfm?Category=122&PartNumber=DSL-1

That may be the simplest option if you want to retain the dynamic oil pressure system.

My Vanagon is too old for the dynamic oil pressure system.  So I just used a tach from an '85 Jetta TD, and when I plugged it into the W signal from my AAZ-engine alternator, it worked fine.  I have an oil pressure gauge that I like better than idiot lights and buzzers, anyway.

If you go that route, you'll have to calibrate the diesel tach, as Murphy's Law says the alternator pulley won't be the same size on your alternator as it was on the car you take the tach from.  I took my car over to a local John Deer tractor dealer, and had them temporarily put their optical tach on the engine while I tuned the adjustment screw on the back of the tach, to calibrate it properly.  

Check this page out, too:
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml

Also, I seem to remember someone once mentioning that it is not rocket science to add a W signal to any Bosch alternator, but I can't give you any more details on that little project.  Once I had a working tachometer in my dash, all these options became pretty academic.

[jackbombay]

Thanks for the post!!

[racer_x]

So my 86 Quantum has the Dynamic oil pressure warning system, IT uses two sensors and RPM input to set off the buzzer. Below 7 PSI at Idlw and you get a light, below ~26 PSI above 2500 RPM and you get abzzer and a flashing light. The 2.0 Audi TD did not come with an alternator so I am using the one off the quantum, but it has no "W" terminal, so I have no RPM input for the Oil pressure warning system which means  (I think) that the car will always think it is Idling so the higher pressure switch will never "be in charge" of the warning.

   The tach in the car is for a 5 banger gasser, if I got a new alt for the Audi 5 banger Diesel with a "W" terminal would it's signal be correct for my existing tach? and what about for the Dynamic oil pressure warning system?

The alternator with the "W" terminal will work for the dynamic oil pressure warning system, but not for the gas tach.

Also, make sure your sender switches are for the diesel engine, not the gas engine. There are two different sensors and the diesel engines use the lower pressure switches. Gas pressure sender switches in a diesel will give you a lot of false alarms.