# Adding a temp gauge to a beetle



## RangeR BoB (Aug 17, 2000)

All:
I want to add a temp gauge to my beetle. I could cut a hose and install a sender. here's the deal, however. there is a perfectly good sensor installed in the car already, I just don't have an easy way to read the circuit.
According to my shop manual, the temp sensor has 4 pins, 2 of which are the temp resistor. The resistance goes from around 1kohms at room temp, to 250 ohms at operating temp (like a standard VDO sender)
Your homework assignment, should you chose to accept it, is to develop a circuit to monitor this resistance, without actually changin it. That way your temp gauge will work, and you don't screw up the engine computer.
Any ideas? Something along the idea of a shunt or brodge, I would guess. Any electrically inclined readers out there?


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## VelvetFoot (Jun 22, 2001)

*Re: Adding a temp gauge to a beetle (RangeR BoB)*

Hi.
I haven't looked into this too much yet, but I did notice that there are 4 wires going to the sender. Are they all used by the engine, or could two of them perhaps be 'vestigial' and available for use. Perhaps there already is something in that sensor that is not being used, since we don't have water temp gauges like Jettas and Golfs.
I did mess around with it previously and I seem to remember that it was more suited to a 300 F degree VDO gauge. That was more than my 250 F water temp gauge I have. So I would need LESS resistance, and I'm not electrical enough to know how to do that.
I did take one of the sensors apart and took a vdo 250 F sender apart as well. There are carbon elements that seem to be interchangeable. Putting the oem sensor back together was a little messy - it was like closing a can or something - but that crimped seal really doesn't have to be waterproof, just weatherproof so I figure silicon would have done it. 
I threw the stuff away, cause I assumed there were only two conductors in the harness, since we don't have a gauge.
Does anybody know for sure what those 4 wires do?


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## VelvetFoot (Jun 22, 2001)

*Re: Adding a temp gauge to a beetle (VelvetFoot)*

On my TDI, according to Bentley, the gauge is two sensors in one. One for the computer and one for the 'gauge'! But Beetles don't have a gauge! What's going on?


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## RangeR BoB (Aug 17, 2000)

*Re: Adding a temp gauge to a beetle (VelvetFoot)*

According to my understanding from the Haynes manual, one set of terminals is for the 'puter, the other is for the ID-10-T lite on the dash.
SO I cut a hose and put a sender there.
I did find that we have a coolant afterrun pump, however. Nifty.


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## paultakeda (May 18, 2002)

*Re: Adding a temp gauge to a beetle (RangeR BoB)*

quote:[HR][/HR]I did find that we have a coolant afterrun pump, however. Nifty.[HR][/HR]​And this is nifty why? Explain, dammit!


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