1990lumi Posted July 30, 2014 Report Share Posted July 30, 2014 replaced all the relays under the hood have new cooling fan it works when hardwired to battery, but it does not kick on when my car is running and the coolant will boil over and spray out the radiator cap and overflow the coolant tank bad coolant switch or something else? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted July 30, 2014 Report Share Posted July 30, 2014 cooling fans are controlled by the ECM, which gets its coolant temp information from the 2-wire coolant temp sensor near the thermostat housing. you'll need to get datastream information to see if the sensor is indicating a coolant temp lower than reality or if the ECM is commanding them on at appropriate times, but they aren't engaged. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted July 31, 2014 Report Share Posted July 31, 2014 try bypassing the relay by jumping 87 to 30 in the fuse box. If the fan comes on then probe the remaining 2 pins for power, should be 12V with ignition on present on one of the pins. The other goes to the PCM and the PCM grounds it to turn it on. If all is well then in theory you have a bad CTS, Like Robert said, the 2-pin one. Quote Link to comment Share on other sites More sharing options...
1990lumi Posted July 31, 2014 Author Report Share Posted July 31, 2014 so either bad cts or ecm Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted July 31, 2014 Report Share Posted July 31, 2014 or a section of the harness requires attention. Quote Link to comment Share on other sites More sharing options...
1990lumi Posted July 31, 2014 Author Report Share Posted July 31, 2014 i just need a second car so i can rip the motor apart rebuild it and replace every sensor and rewire a new harness in this one Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted July 31, 2014 Report Share Posted July 31, 2014 or a section of the harness requires attention. THIS for the 3rd time ive had a cooling fan issue on a car and it was the harness rubbed through on the upper dogbone mounts. for some reason the fan wires were all the way at the top of the loom and got rubbed through...lost 1 fan then the other. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted August 1, 2014 Report Share Posted August 1, 2014 I don't know what year this car is but on my First Gen the fan wires come from below. Quote Link to comment Share on other sites More sharing options...
1990lumi Posted August 1, 2014 Author Report Share Posted August 1, 2014 its for a 1990 lumina Quote Link to comment Share on other sites More sharing options...
Imp558 Posted August 1, 2014 Report Share Posted August 1, 2014 its for a 1990 lumina Yeah, and for some reason I didn't figuere out that "1990Lumi" owned a 1990 Lumina all by myself. I gotta get back on the meds. Quote Link to comment Share on other sites More sharing options...
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