Coolant Temperature Sensor--2 pins?

[bsharp8256]

Hey everyone, new MB owner here.

I've got a '73 350SL, and the temp gauge is totally dead. Using an infrared thermometer I can tell that the temperature is fine, but in any case it's something I'd like to fix since it'll be my daily driver starting this week. I figured the best place to start would be with the sensor/sender, but I can't seem to find the correct one anywhere! I got tired of looking and called my closest dealership, and they told me it would be about $115...

So now, with new motivation, I come to you guys for help. The problem is that all the parts stores and sites say I need a 1-pin connector for a gauge, and a 3-pin for a temp light (which I don't have). Mine is a 2-pin connector with a plug, and I haven't seen this referenced anywhere. I could run out and pull it for some pictures real quick, but I'm at work and it's raining, so I'd rather not if someone has some past experience with this. To avoid confusion, I guess now is also the time to mention that it is a 73 350; the vin is 107043-prefixed. I don't see any reason why they'd use different sensors, but you never know.

Thanks!

[mbboy]

Google Mercedes 0280130014, and see if that's the 2-pronged sensor you have. If it is, you may have a 1972 350, as it seems that the '73 did have a single connector.

Good luck

[bsharp8256]

No, that was the wrong one. Maybe I'm calling it by the wrong name? In any case, here are some pics. In the first one, the blue arrow points to the one in the link you gave me, and the red one is the one that (I think) I need. The second picture didn't come out as clear as I had hoped, but it should give an idea of what it looks like under the plug.

Thanks for your help!

[mbboy]

If you're talking about the thing with the two white ears on it, those are vacuum ports, and the thing itself is a called thermo-vacuum switch.

They come in different colors, and I can't really tell what color your is.

[bsharp8256]

Ah thank you! A quick search found the part. Fortunately, since I was totally wrong about what it was, it turns out I don't need a new one after all. My car starts fine in the cold. Unfortunately, that means I still don't have a working temp gauge.

I actually replaced the other sensor you linked me earlier a few days ago--I believe that's temp sensor #2 in a D-jet system, correct? What would you suggest checking first to get the temp gauge working again?

Thanks,
Brandon

[RadioTek]

The two sensors that you are pointing to don't have annything to do with your temp guage. the one on the left with the two big terminals is the 100 degree c switch for the aux iliary fan, and the other one with the small terminals ( the same as on your fuel injectors) is Temp Sensor 2 for the D-Jet injection system.

The guage sensor has a single terminal, and is located toaward the back of the heads, either on the left or right one depending on year. They're usually near the rearmost injector.

Hope this helps,
Scott

[mbboy]

After looking closer at the 2- terminal switch, the two connectors I thought were the ports of a thermo-vacuum valve do look more like plugs. So, I'll defer to Scott on this, as he evidently knows more about your car and your problem than I do.

Good luck with your gauge problem

Originally Posted by RadioTek

The two sensors that you are pointing to don't have annything to do with your temp guage. the one on the left with the two big terminals is the 100 degree c switch for the aux iliary fan, and the other one with the small terminals ( the same as on your fuel injectors) is Temp Sensor 2 for the D-Jet injection system.

The guage sensor has a single terminal, and is located toaward the back of the heads, either on the left or right one depending on year. They're usually near the rearmost injector.

Hope this helps,
Scott

[cushjbc]

bsharp,

The sensors in your pictures are a thermal-time switch used for cold starts in conjuction with your start valve, and a coolant temp sensor (T2) that sends resistance signals to the D-Jet computer (ECU). They are not related to your inoperative temp gauge.

The temp sensor for the temp gauge in your instrument cluster is located at the aft, inboard end of your right (passenger side) cylinder head closest to the exhaust valve of cylinder #4. You can see it better if you remove your air cleaner and the vacuum hose at the aft end of the right valve cover.

I have spares but we should make sure yours is broken first.

1. Find the sensor
2. Make sure the wire is connected
3. If the wire is connected and the temp gauge is inoperative, do a continuity check from the connector to the #4 terminal of the #1 instrument cluster connector.

[bsharp8256]

Thanks for the replies everyone, you've awesome and it looks like I'll have something to do this weekend.