Car Overheats With A/c On Only.

Discussion in '1994 - 1995 Specific Tech' started by Twista, Aug 25, 2013.

  1. Can anyone test this out for me. With your car on and a/c on your fan should be running @ HIGH. Now unplug the ECT sensor (while a/c+high speed on) does your fan speed change at all or does it stay the same.

    With my car and the high speed fan on and i unplug the ECT sensor the fan ROMPS up higher and spins faster. So it seems my fan is running in medium speed when Highspeed is triggered with the manual switch. Without the switch installed it runs in Normal mode with the A/C on.

    Now i unplugged the ECT sensor with the fan spinning @ super high my temp still are about 215-220 with the a/c in this weather.


    I turn the A/c off the temp slowly drops back down to about 200. If i idle it drops to 195. A/C back on and driving its up to 230 again.

    So im stuck here today deciding if i should drop $160 on a brand new fan or not. Im really hesitant because i dropped so much money on this issue and the fact the car still gets HOT with the fan on super high. For all i know the fan could be turning off while im driving and turning back on when i stop.

    Car is pretty much stock. besides full exhaust..
    Stock fan and shroud
    Its 90 degrees outside right now.

    What i changed so far:
    Radiator to new oe style radiator
    Waterpump
    Thermostat
    ECT sensor
    New Sensor
    Fan switch for High
    Mechanical temp gauge
    drained system and added new coolant with new radiator (no flush)


    What i havent done is:
    Changed to a NEW oem fan
    Flush the coolant system with chemicals

    What would you guys do in my shoes? Besides ripping out the A/C
     
    #1 Twista, Aug 25, 2013
    Last edited: Aug 25, 2013
  2. parts store junk ect sensor or motorcraft?
     
  3. check your grounds. a bad ground can peg out your gauges when there is a load placed on the alternator.
     
  4. I eliminated the stock gauge for a mechanic gauge so i get the real temp.

    2 different part store ones. Problem remains.
     
  5. If your fan is kicking into high with an override switch then it's not the fan.

    Were it me, I would start with a wiring diagram so that you can map the sequence of events that cause the fan to go into high speed. You shouldn't have to run many traces if that's the only problem.

    One other thing that comes to mind is sealing the air gap between the radiator and the condenser. I saw that you said you changed radiators out. Folks often neglect that little detail. You can use the adhesive foam weather strips that you would find in any hardware store. The path of least resistance for air is the gap between these two surfaces... Sealing that gap will ensure air is being pulled through both heat exchangers.


    Mustang-94-95-CCRM-AC-Diagram[1].gif
    Diagram courtesy of www.veryuseful.com
     
  6. Belt tensioner?
     
  7. Yeah, either the belt is a little too long and the tensioner is bottoming out when the AC is on, or the tensioner itself isn't providing the required belt tension.
     
  8. New project right there :nice:.....hmmmmm, ...... got any pics??
     
  9. Car seems to running @ 210-215ish now max in 85 degree weather with the a/c on forever. Doesn't climb like it did.

    So im happy. I just installed a new air deflector to replace the missing one.
     

  10. Yeah...

    7feff883-4120-4792-b790-d79550d3911f_300[1].jpg

    Apply between condenser and radiator. :D
     

  11. Going to do that also. since i figured out my main problem. Anything else wouldnt hurt.
    Do you have any pictures where you applied it to? Like what areas exactly?
     
  12. This image is from a different car but you get the idea. Apply the weather strip around either the condenser or radiator so that there's no air gap in-between. This forces the air to go through both vs. being drawn from the gap at the outside edge between the radiator and condenser.
    2012-03-20184122[1].jpg