temp gauge not working after head swap

I have a 99 Legacy 2.2 auto. I swapped a pair of '00 2.5 heads onto it (the stock heads were junk). The 2.5 SOHC heads only required a Y-pipe change. Except I have a single yellow/blue wire that ran to a point (sensor?) threaded into the stock right head. The new head doesn't have that point. And now my temp gauge doesn't work. Does that wire control my gauge and is that missing piece the feed? I don't have the old heads anymore to visually compare.

the temp gauge sending unit is typically located in the coolant ''crossover pipe'' under the intake manifold on the passenger side.

(follow the pipe back from the top rad hose.)

 

i'm nor familiar with the 99 ej22 setup,

but the 90 - 98 phase 1 engines (including the 99 DOHC engines) have 2 temp sensors.

the 2 wire unit is for the ECU,

the one wire unit is for the temp gauge.

 

the phase 2 ej25 engines have a single unit, with 3 wires.

 

since you removed the intake manifold, i suggest you look for the temp sensor with no wire attached.

this assumes that the 99ej22 phase 2 engine has 2 sensors.

(EDIT: rockauto suggests that the 99 ej22 has 2 sensors.)

 

phase 1 engine crossover pipe below, item #5.

the 2 temp sensors are #1 and #4.

 

http://static.opposedforces.com/epc_img/366494903601.png

or,

 

there have been issues with the aftermarket, phase 2, 3 wire, replacement units being bad, not working, right out of the box.

was it replaced?

 

or,

the pins in the sending unit connector are pretty flimsy.

make sure they are not damaged or bent.