Having a problem with my temp gauge. I took the sender out and tested it and it seems to be roughly within spec, 61 ohms at 82C, 105 ohms at 60C, and I brushed the inside of the connector as best I could but the gauge itself never moves. I even tried grounding that connector for a second to see if the needle jumped, but it didn't.

So now I have my instrument cluster out of the car now and I wanted to see if I could ground out the gauge to at least see the needle jump.

The body electrical system doc showed me which pin it was on the connector (circled in red below), but I'm not sure how to test the gauge out of the car. Maybe I need to give the whole unit 12V and a ground, and then ground out the TEMP pin? Or take it apart further and test the gauge itself?

 

The Black/Yellow wire to the gauge cluster (ME-01) supplies voltage to the gauges. The Yellow /White wire to the cluster (ME-02) supplies a ground signal to the gauge from the temp sender. Thus you need the pin for voltage connected to voltage and the pin for the temp sender connected very briefly to a ground to get the gauge pin to move. If the ground is supplied too long the gauge can be damaged. You don't want to peg the needle. ME-01 and ME-02 are both round plugs. It's also possible that the pin in ME-02 for the Black wire might need to be grounded but not likely (Black wire supplies a ground to the gauge cluster).

 

I just tested connectivity from the sender to the ME-02 pin on the black connector and that was fine, so everything is pointing to a bad gauge.

Does anyone make an aftermarket gauge that operates in roughly the same ohm range as stock? Every gauge I see that posts specs seems to talk about 1000-2000 ohms, while the factory gauge is more like around 50-200 ohms.

Really sucks that the sender is 1/8" BSPP too, although I snapped one off in the block this weekend and was able to easily unscrew it with a screw extractor by hand since it's not tapered, but the problem is most aftermarket gauge senders are 1/8" NPT which might fit but won't have a very good seal.

 

why should you use the stock location when there are other locations available to put an aftermarket sender?.
Think outside the STOCK box...and go with a new location,leave the old sender hooked in and use a new gauge with new sender in another location.

 

I've successfully (and with no drama) installed 1/8NPT sending units into the stock hole...twice now, in fact.
Mr. S does have a point however, you can find other suitable locations; some more useful than others depending on your option package.

 

Me Japanese...

Me play joke...

British pipe thread muffuka...

 

I thought about giving the NPT sensor a shot since the threads are almost identical. Did you use teflon tape or pipe dope to help with the seal?

I saw a few posts about drilling and tapping into the block but that makes me nervous. With my luck I'd drill through a water jacket and into an oil passage.

Wound up going the lazy way. I bought one of those $10-$15 inline aluminum adapters with 1/8" NPT threads to put in the upper radiator hose with an Autometer gauge to mount on the A-pillar. I realize it will only give me a reading after the t-stat opens but I'm ok with that. I hope I measured it right. Seems to be 1-1/2" (38mm) I.D.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

 

best place to put an aftermarket gauge if you want to leave everything else intact, is in the BAC coolant line. That line is not affected by the thermostat.

 

You know, in theory that sounds great but in my limited experience (only two engine refurbs, both S5 NA) that loop is awful.
For a coupla reasons.

-The "heatsink" on the BAC is a joke and there's no way it does anything meaningful.
Yeah, I know it's really a sorta reverse heatsink- meant to induct/stabilize heat, rather than conduct it away- but the contact patch between the water fitting and the BAC valve is awful and can hardly be doing any more heat stabilization than the the surrounding air alone.
In other words, the BAC location (again, on a S5 NA) is already heatsoaked more than that little water line/sink will ever achieve.

-I've torn down several throttle bodies and every one has had all sorts of crud/grit in the thermowax area. I suspect this is due to the fact that the top of the thermowax is the highest point in the cooling system, yet there is no provision for an air bleed, so the water flow through that sub-circuit is inconsistent and subject to blockage.

I don't see a real downside to the upper rad hose location other than the temp gauge may take a bit longer to begin reading after a cold start but you're certainly getting full coolant flow over your sensor.