I did a head gasket job on my 02 disco back in December, she has 165,000+ on so I figure it was time. That job went well, and from reading on here about the dummy light I decided to add an aftermarket temp gauge made by Bosch. It seemed to be pretty straightforward coming out of the package. It has 3 posts on the backside, one for 12v,one for ground and one for the temp sensor (sending unit). I thought I could get away with tapping into the existing sending unit wires, and the gauge worked except it triggered a trouble code and the red dummy light lit up and the needle never rose above cold. So I undid the wiring to the new gauge and everything went back to normal. Here's where my headache begins, I bought from glow shift a tee adapter (the gs-aw32) and decided to add a sending unit in my top hose. The only problem is now the Bosch gauge isn't working, the gauge itself is grounded to the engine ground on the firewall, I have the 12v power hooked up, and the sending unit is hooked up but to no avail. I called Bosch and spoke to tech support and they suggested that I ground the tee from glow shift so I did, still to no avail.

Can anyone here help me figure this out?

 

Send back what you bought and buy an UltraGauge. Why make this more difficult than it needs to be?

 

I recommend the Autool because it is easier to mount, and matches the dash light color. Also like the ultragauge it has a settable alarm. That said, how many wires does your new sending unit have? What is the PN of the gauge you bought?

 

It has 1 wire on the sending unit and the gauge is already mounted and I'm not concerned with color matching. The part # is FST-8211

 

My guess is you don't have the sending unit adequately grounded, post a pic of your install.

 

So after driving around a while the other day my aftermarket gauge started working, I suppose I wasn't giving it enough time to get a reading. Although it takes about 15 minutes to start climbing, is that normal for it to take so long to start showing a reading?

 

It depends what the low end of your gauge starts at.

 

The lowest is 100° and the highest is 280°.
I also have the sending unit in the hose that is held down by the top half of the fan shroud, and I understand that being in that location I won't get a 100% accurate reading. I had my code reader hooked up and there was about a 15° difference