I got a guage for trade from a buddy, it's a water temp guage, it comes with a thermal sensor, my question is this: can i tie in with the factory wiring and route it to the guage instead of using thier temp sender unit and still get the propper readings ? I want to do this because i wont have a free spot on the manafold for two water temp sensors...

 

Check both senders resistance in a hot and cold condition. Could be done with a stove and a glass of ice water. If they read the same you can use either one you want otherwise your gauge or cpu will get improper readings if you use only one or the other.

One thing to keep in mind if you can use the original sensor for both. Piggybacking a cpu circuit can cause problems with the readings that get sent to the cpu.

 

Your car should have two sensors anyways. You can't tie into the one that runs to the ECU, as it will affect the reading, and it is a 5 volt reference. Just remove the one that controls your factory gauge(or idiot light), and replace it with the one that came with with gauge. You *may* get lucky, and be able to use the factory sender. Should be located in the drivers side head with a single green wire leading to it. To test it properly like dankhound said, you will need to remove it anyways, so just put in the proper sender to begin with.