88 5kq - want to add oil pressure and voltage gauges

[Huw Powell]

> I want to add oil pressure and a battery voltage gauges on my 1988 5kq.
> The factory gauge cluster only has fuel and water temp gauges.
> 
> I have an old (20yrs) Stewart Warner 3 gauge set (oil, water temp, voltage)
> available.

> All 3 gauge inputs are electrical.
> The electric gauge I would hook up to the alternator sensor wire post.

Or any "key on" hot wire would work (usually blue/black).

> I'm not sure what to do about the oil pressure connection. The original
> Stewart/Warner gauge came equiped with a rather large, leaky, mechanical
> "pressure/voltage" transducer. I'm assuming that inside the transducer was a
> mechanically operated variable resistor.
> 
> I assume that the car oil pressure sender is of the idiot light design . .
> .on/off pressure switch, or is it?

Usually the set up is two on/off type senders, a low and "high" one. 
They feed into a control unit that also gets tach information.  At low 
revs, the low sender must be triggered to fire the warning light/buzzer. 
  At higher revs, all that is needed is for the "high" sender to 
trigger.  I think they are something like 0.8 and 1.8 bar, but that is a 
bit of a guess.

> In models with an oil pressure gauge, does the car not also have an idiot
> light warning for low oil pressure?

On oil pressure gauge cars, one of the senders has two connections - one 
for the warning light system, and one that is variable for the gauge.

> Anyone want to discuss the Theory of Operation of the audi oil pressure
> transducer?

I think I just did...

> Maybe I can adapt the Stewart/Warner oil pressure gauge to work with the
> audi system - maybe a resistor network to modify the input signal - or
> replace/add an audi pressure transducer.

You might see if you can get a set of used type 85/89 auxiliary gauges 
and senders - they might mount in your S/W pod if you are lucky.

The third gauge often found (on your donor Audis) is an oil temperature 
gauge, which is driven by a sender mounted in the bottom of the oil pump.

Each of the two gauge circuits are driven by 12 volts applied at the 
gauge; all three have easy to replace little bulbs in sockets.  Often if 
you find a donor set, you will also get a bunch of wires that make your 
connections simpler (one ground, one power wire, one light wire, two 
wires for senders).  Just make sure that if you buy a set, it also 
includes the oil temp sender and the two pin oil pressure sender.  And, 
ideally, some copies of the manual pages showing wire colors...

PS, I just installed a set of these along with one or two others in a 
1957 Trojan loader instrument panel...

-- 
Huw Powell


http://www.humanspeakers.com/loader

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