Temp gauge no workie...
 

so I get home early and find my sparkling, brand-new temp sender in the mail.

Before I start my question, I have a little story... The reason I bought this was because on our last mini-roundup in Giddings, just before I got home, I hit a bump in the road (expansion crack) and my temp gauge jumped totally to the right - HOT setting... I mean instantly from 1/3 temp, to full right - hot. I know i've had problems with the sender in the past.

so I go and remove the 'old' sender, burn my hands, and then put the new one in. Hook up the wire, go to start it, but now it just stays full-cold, at the left - doesn't even move a tiny bit...

any ideas? I checked all my fuses - nothing blown. I can only assume the gauge is OK because it's new (it's not like there's much to go wrong with one, right?). I used to be able to sping the 'white tube' which goes into the sender on my old unit - this would essentially allow me to dial in the starting setting on the gauge. The new one I can't do this.

can we calibrate these things? I don't think so but am I missing anything obvious...

ok, little update

I let the car cool off for 1/2 an hour. When I started it up, the gauge had MOVED! The only problem, is that it started just over the 'cold' line, and gradually got COLDER.

Somehow the polarity of the wire is wrong? Could it be anything else?

I have to tap on mine to get it to move on first startup...it's good for the day after that.

sjd

wrong sender, right Troy?

think so - like you mentioned, probably for a VW - that's EBay for ya

Well, if its like we discussed and the guage works the opposite direction from normal, its that NTC PTC thing - I heard once that Bug senders worked the opposite- for a 912 the resistance of the sender increases as the temperature increases... PTC.

yeah, I just 'verified' this morning, that the gauge is pegged 'hot' upon startup, and then shows colder as my engine heats up. Unfortunately, it goes too far and pegs left...

we could mess with parallel resistors to get it to stabilize somewhere in the middle when its warm but the variation would still be extreme and reversed. Maybe a local bug shop will trade you a spark plug for it or something.... :)

Dang Troy...using VW parts on a Porsche? What were you thinking!!! By the way...a VW oil pressure sender for a 1600 T1 works great on a 912!!

cool.... we need to make a list of this stuff someday

SSSShhhhh...we don't want people knowing all of our secrets!!!

Kev,

If you're gonna list your vehicles in your signature, you should be honest!

Lol...yeah I need to update it it seems...some have come and gone since then...

To find a good temp sender for your 912 measure the resistance between contact pin and housing:
- about 120 ohm at 20 degrees C
- about 145 ohm at 60 degrees C. You can heat the sender with a cigarette lighter and the resistance must go UP.
PTC= positive temperature coefficient= resistance increase with temp
NTC negative..= resistance decreases with temp
So the 912 temp sender is PTC resistance.

To check your dash temperature dial:
-pull the sender wire off
-take a 200ohm 1watt resistor (any electronic shop can supply)
-connect one end of the resistor to the sender wire, other end to the chassis.
-your temp meter should go to the red line= about 100 degrees C.

Happy to help,
Patrick