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914World.com _ 914World Garage _ BigMark Oil Temp Gauge Wacky on a 6 - Help
Posted by: RickS Jun 12 2011, 11:14 PM
Bought one of BigMark's excellent quad gauges (oil temp, pressure, fuel and volts). When oil temp was connected to the 2 ltr four, when the car was cold, the temp would show zero and then gain as the engine warms. With the new 3.0 6, the gauge when starting a cold motor shows ~ 125* and then climbs from there. Seeing temps around 250+ can be a bit disconserting, until you do the math. BigMark doesn't have a solution for the gauge readings. I used a Porsche temp sender as well as one Mark included and they both read about the same.
Soooooooooo... any thoughts on how to recalibrate the temp gauge or sender to accurately reflec the actual temps? What is going on here?
Much grass.
Posted by: McMark Jun 12 2011, 11:17 PM
I don't have a solution for you, but.
Different Mark. 
I changed the title.
http://www.914world.com/bbs2/index.php?showtopic=66564
Posted by: kg6dxn Jun 12 2011, 11:20 PM
Install an engine ground strap.
If the sending units are the same value and the only difference is the engine, it is a difference in resistance to ground giving you the reading.
Posted by: RickS Jun 14 2011, 09:30 PM
Install an engine ground strap.
If the sending units are the same value and the only difference is the engine, it is a difference in resistance to ground giving you the reading.
Unfortunately there is a ground strap from the trans to the underside of the rear trunk just behind the center of the muffler.
Must be a compatibility problem between the sender and the guage - McMark, is there a specific rating or nomeclature for the gauge which must match the sender?
Posted by: McMark Jun 14 2011, 10:20 PM
Again... not my gauges. 
But, I think I can help. You probably have a corroded connection somewhere. Try running a long wire directly from the sender to the gauge and see if that solves the problem. Just run it temporarily at first to see if it fixes anything.
Also try unplugging the wire at the gauge and turn on the key. What does the gauge read with the sensor wire unhooked?
Posted by: RickS Jun 14 2011, 10:27 PM
Again... not my gauges.
But, I think I can help. You probably have a corroded connection somewhere. Try running a long wire directly from the sender to the gauge and see if that solves the problem. Just run it temporarily at first to see if it fixes anything.
Also try unplugging the wire at the gauge and turn on the key. What does the gauge read with the sensor wire unhooked?
Sorry Mark - not trying to diss you, or any other people with your first name (or aliases of Mark or those in the witness protection program, no matter how heinous their crimes).
Great suggestions - thanks.
Posted by: rick 918-S Jun 14 2011, 10:32 PM
if the sender and gauge aren't talking the same language and you have ruled out a ground issue and it's wired correctly, put a potensiometer in line and zero the gauge when cold. Also, if it worked correctly with the 4 cylinder sender can you use that?
Posted by: ConeDodger Jun 14 2011, 10:43 PM
Did you by any chance use pipe thread tape on the sender? It must be put on metal to metal for grounding purposes.
Posted by: RickS Jun 15 2011, 10:50 PM
Did you by any chance use pipe thread tape on the sender? It must be put on metal to metal for grounding purposes.
Good thought - Let me talk to the guy who did the work.
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