Hey everyone.. me again with my turdbox 89 hatch.I recently threw a rod through the side of my d15b2 and picked up a low mileage d15b7 for a decent price from a trusted shop, took old motor out swapped in d15b7 and extended the fan wires (since the b7's fan switch is on the thermostat housing , not on back of block like b1/b2) and started car up after installing everything else. Motor runs great! But started over heating (if it wasnt for knowing what a over heating motor smells like. Wouldn't know it was, cause even my temp gauge isnt isnt working!). Fans won't come on at all unless I unplug the connector and jump the wires. I replaced the switch twice, still nothing, thermostat is fine, car runs perfectly cool when I jump the fans to stay on. All grounds are in place (One on trans that is the battery ground, One on the valve cover to the rad support, and 2 that go to the thermostat housing.) Second problem is my temperature gauge doesn't work correctly anymore, once car warmed up it would be directly on the C. When it was over heating it was slightly above the C. Took cluster apart to see if it was the gauge itself, when I unplugged one of the connectors for the cluster (the connector that makes the instrument lights work) the gauge works fine. Goes right to the middle (operating temp) as soon as I plug it back in, it drops back down. Same thing used to happen with my fuel gauge. But opposite. (Fuel gauge would peg full no matter what, 4 different clusters and 6 different sending units, finally hooked up an aftermarket one) Any help would be appreciated

 

Do you have a multimeter?

Which wires are you jumping? Straight to the battery? Have you tested for 12v at fan connector? Checked under dash fuse 15? Does your relay click (no idea where it’s at tbh)? The relay grounds at G201 which is left inner fender (in engine bay) near windshield washer reservoir.

As for the temp gauge not working - try cleaning up the ground on inside driver side (assuming North America) footwell? I believe that’s where it grounds. There’s also a ground near bottom of steering shaft check that out.

Just curious if you have a instrument cluster lighting dimmer switch?

 

The 2 wires that come off the back of the block, radiator fan switch , usually it's on the back of the block with a 2 prong connector, on the b7 it's moved to the thermostat housing. If you ground the wires together it kicks the fans on and they run constantly. I get 12v at the fans and at the relay. Fans work fine unless I plug them into the fan switch. Fan switch is brand new replaced twice thinking I got bad one from store. I do have an instrument cluster dimmer switch ,

 

 

Changed out the ECT and the coolant temp sending unit again and traced the wires while replacing the thermostat and the water pump and magically the temp gauge works again but fans still won't turn on by themselves...