Originally Posted by tableclocks
my 1994 van 350 temp gage dont work..new sending unit did not help...i changed it to a mechanilal gage and the engine runs rough...so i need the oringial for the 2nd wire on it that goes to the ECM..so it'll run right....can i add a Tee and use the orinigal and the machanical..i do have the room....but will i get enough water in the Tee for the reading to be resonabe ?..thanks for looking and your help...richard...firstname.lastname@example.org
X2 on DoubleVision's comments. The proper place for a gauge sender (mechanical or electrical) is where the plug fitting is located on the exhaust side of the drivers side head. This is located just about between the pair of center exhaust valves which is the hottest place on the drivers side head which runs hotter than the passenger side due to the natural flow imbalance of coolant induced by the direction of pump rotation. If there is a failure of cooling, this location shows the extreme firstest and mostest.
The sensor by the coolant return is a data feed to the computer, it has a different purpose than keeping track of the hottest place on the engine's cooling system. So it is located close to where it gets an average of the return coolant temp. This is used to compute both cold start enrichment (choke) and temperature as it contributes to changes of air density within the intake. This is why you're getting rough running. This sender needs to be installed as the factory has it, not on a tee.