Cluster Temperature Needle Calibration

[puchak]

I'm sure this could be useful for anyone fixing/restoring their cluster. I've done some digging around but can't get a good answer nor does anyone seem to really have this issue.

I went through and restored my cluster. New housing, buffed and polished screen, gauge faces replaced, and lastly needles touched up or replaced where needed. Novus 1-3 is your best friend.

However, this is where it goes wrong -- the engine temperature needles are reading slightly off now... The temperature reads at a very low 80 degrees on my 300TE. I'm pretty sure this was higher before I started fiddling with the cluster, and I've read these Mercedes engines run on the hotter end. Sitting around it doesn't get close to a 90 degree temperature, maybe 83-85 at the most.

I have a good idea of where the needle should sit at a starting point, but I want to know for sure for comparison.

So, my question is: What is the best way to measure the temperature so I can then adjust the cluster needle to represent this? At a very basic level, I'm guessing a temperature gun used somewhere would be best.

 

[gsxr]

For a 1993 300TE with HFM (that's what you have, correct?) or any 400E/500E, the best method would be to connect an SDS with HHT-Win and read the exact coolant temp from live data, and adjust the gauge needle until it matches. Best to calibrate at 80°C or 100°C since there are clear lines at those temps, and that's where you want the most accuracy. Accuracy may vary a few degrees over the full range of movement.

Without SDS, it will be more difficult. IR guns will get you in the ballpark.

 

[puchak]

Correct on the 1993 300TE. I don't have access to an SDS, my shop guy may have one - I'd have to ask. Where could I point the IR gun for said ballpark?

 

[gerryvz]

How do you adjust the gauge needle? Is there a defined process?

 

[puchak]

Once you pull out the cluster, you remove the screws on the back of the cluster, then you have access to all the faces and needles. From there you can pop off the needles with a plastic tool and adjust the resting spot with fine measurements. It's what I did with my speedometer that was off around ~8mph.

 

[gsxr]

Where could I point the IR gun for said ballpark?

Ideally, point near the 1-pin temp sending unit that is the source for the temp gauge. I forget where that is located on the M104 but it may be near the radiator hose water outlet from the cylinder head.

 

[puchak]

The car is a 4Matic so it only got the M103 in the US.

 

[gsxr]

Ohhhhhh. Forget the SDS then... no live data from the M103. You're stuck using an IR gun.

It helps if you post the year and specific model in question, especially if the car is not a 400E/500E. The engine management systems are in different solar systems between the M103 and M119.97x powerplants. In this case you'd need to have mentioned 4Matic, as the RWD 1993 300TE's had M104 with HFM and live data.

 

[puchak]

Good to know! I didn't think there was SDS available but I had to confirm. I remember reading that clearing error codes was super simple, which would explain the lack of SDS.

Thanks for the pointer on the sending unit.

 

[rayhennig]

Not much help but the temp/oil/fuel gauge was replaced on my 124 300CE-24 and the gauge now reads about 10C too high. IR gun says 87, gauge says just under 100, about 97?

Not too bothered but I'd like to fix it.

RayH