pcristquester Posted November 20, 2014 Report Share Posted November 20, 2014 My pusher/AC condenser fan doesn't run when the AC is on. Checked that it works when supplied with 12v and ground to the proper terminals on the connector. Tried swapping thermosensor number 2 and still no go. I have about 12v to the blue/red wire all the time and 14v when car is running, but the blue/yellow doesn't seem to be grounding out to complete the circuit to kick the fan on when its supposed to. Thanks in advance peeps Link to comment Share on other sites More sharing options...
ucw458 Posted November 20, 2014 Report Share Posted November 20, 2014 The relay tree next to the battery has a relay just for the pusher fan. Check there. Link to comment Share on other sites More sharing options...
pcristquester Posted November 20, 2014 Author Report Share Posted November 20, 2014 I swapped the relay with another unknown condition relay from my other car, no change. How do I test the relay? Link to comment Share on other sites More sharing options...
ucw458 Posted November 20, 2014 Report Share Posted November 20, 2014 Ground both temp switch wires on the radiator. All 3 fans should come on. If not then the relay is bad or there's no power going to the relay. Link to comment Share on other sites More sharing options...
pcristquester Posted November 20, 2014 Author Report Share Posted November 20, 2014 Will do. Thanks Jeff Link to comment Share on other sites More sharing options...
alp247 Posted November 20, 2014 Report Share Posted November 20, 2014 I had this same issue and it ended up being the sensor on the thermostat housing. I chceck all the relays and the pusher fan and that was the last thing. after i changed it from my other car (AC Delete) the fan started working. If you are worried about the car getting hot when the AC is on you can ground that wire for now and it will come on automatically when the AC is turned on. Link to comment Share on other sites More sharing options...
pcristquester Posted November 21, 2014 Author Report Share Posted November 21, 2014 I'll try that too, but want everything to work as designed. My understanding of that sensors' function is to shut off the compressor when coolant temp gets above 235? Link to comment Share on other sites More sharing options...
alp247 Posted November 21, 2014 Report Share Posted November 21, 2014 yes that is the function of that sensor. Link to comment Share on other sites More sharing options...
mikec Posted November 22, 2014 Report Share Posted November 22, 2014 There are two fairly independent wiring circuits to the fans on 87-later cars. One is for normal engine cooling mode and the other is controlled by the a/c computer: The primary and secondary fans each have two relays that can run them: one relay for the engine-side cooling function and a second relay for the a/c function. The pusher fan has just one relay but two different things can activate that relay. Engine cooling: simple temp sensors and relays... no computers involved:* temperature sensor switch underneath "primary" fan trips a relay which in turn makes that fan run when radiator water temp reaches a certain point, roughly middle of the dash temp gauge.* temperature sensor switch underneath "secondary" fan trips two relays which makes that fan AND the front pusher fan run when radiator water temp gets even hotter, roughly 2/3rd to 3/4s on the dash temp gauge. Ergo all three fans should be ON at this point... A/C mode:* A/C computer uses two relays to run the primary and secondary fan whenever the a/c computer cycles the compressor clutch ON; these are different relays than the ones triggered by the radiator temp switches for engine-cooling mode.* a pressure sensor in the a/c refrigerant lines triggers the pusher fan relay IF the refrigerant pressures get higher than normal - indicating a/c operation on a hot day. Because of the engine-cooling relay wiring, there is feedback that causes the secondary fan's engine-cooling relay to trip (running the secondary fan) even though the secondary fan should already running from an a/c controlled relay just described. Look at the a/c refrigerant lines between the headlights and near the a/c receiver/dryer tank... you'll see two different sensors in that piping. One is the "dual pressure switch" that protects the a/c system components from too little or too much refrigerant* if there is too little refrigerant, the compressor OFF pressures will be really low and the switch will OPEN preventing the compressor from running; this protects it from running without the oil that's also in the refrigerant.* if the a/c refrigerant pressures get dangerously high for some reason - too much refrigerant, blockages in the system, lousy airflow through the condensor (front radiator), etc - the high-side of this switch opens to cut off the compressor before the pipes burst. The other sensor switch - the smaller one if I remember correctly with black and black+yellow wires in the harness side of the connector - is the pressure switch that trips when the a/c is working hard on a hot day... i.e. when refrigerant pressures are normal-high. You can unplug the connector on this one and jumper across it as a test, that should run the pusher and secondary fans. Running the a/c on a cool day though generally won't generate normal-high refrigerant pressure so the pusher fan won't run. So I wouldn't worry about "pusher fan doesn't run when air conditioner is on" as that's normal if the outside air temp isn't high. mike c. edit: the little temp sensor switch on the thermostat housing is the ground for the compressor clutch relay; this switch is normally closed unless the coolant temps are dangerously high - then the switch OPENs to kill the a/c in an effort to help save your engine from overheating. This sensor tends to rot internally (the connector tang will spin easily when this happens) rendering the a/c clutch/compressor totally inoperative. Very common failure. Link to comment Share on other sites More sharing options...
pcristquester Posted November 22, 2014 Author Report Share Posted November 22, 2014 Well done mikec! I hope I can someday understand people's questions and be able to break it down so thoroughly and clearly like you have. Obviously, my assumption about the pusher fan operating always when the AC is on was wrong. I was wondering about that pressure switch too, so now you've taught me how to test it as well. Thank you so much!Parker Link to comment Share on other sites More sharing options...
pcristquester Posted November 22, 2014 Author Report Share Posted November 22, 2014 Jumper at the pressure switch confirmed it's all good! Guess I've either never ran it in hot enough weather or didn't pay attention to which fans run when. Thank you guys Link to comment Share on other sites More sharing options...
vbrad511 Posted November 23, 2014 Report Share Posted November 23, 2014 I ran a jumper between my secondary fan and the pusher. When it warms up all 3 kick on. Honestly don't remember if it comes on with the ac anymore... Link to comment Share on other sites More sharing options...
ucw458 Posted November 23, 2014 Report Share Posted November 23, 2014 I ran a jumper between my secondary fan and the pusher. When it warms up all 3 kick on. Honestly don't remember if it comes on with the ac anymore... That's kinda redundant. If you ground the secondary temp switch wire the pusher fan comes on as well. That's how it's wired from the factory. Jumper the 2 temp switches and all 3 come on. Link to comment Share on other sites More sharing options...
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