cooling fan failure - Solved!
06-03-2009, 11:01 AM
#31
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Thread Starter
I think you have a wiring problem. The fans get their power from the relay. If you remove the relay, they should stop. If they do not, they are getting power from somewhere else and in order for that to happen, the wiring has been "improved". At least that is the way I interpret the wiring diagram.
06-03-2009, 02:14 PM
#32
06-03-2009, 04:58 PM
#36
Three Wheelin'
I am no wiring genius, but the way I interpret Wiring Diagram Type 944, 944 Turbo Model 86 Sheet 9, the coolant fan relay is shown at address E/F 56...
N34 is connected to the fan relay which comes from the high side of the radiator temperature switch and the refrigerant switch. When either of these close, the fans run at high speed since they are not going through the resistors.
Do you see the same thing, or do I need to get new glasses? These things are very hard to decipher for us non EE types.
N34 is connected to the fan relay which comes from the high side of the radiator temperature switch and the refrigerant switch. When either of these close, the fans run at high speed since they are not going through the resistors.
Do you see the same thing, or do I need to get new glasses? These things are very hard to decipher for us non EE types.
06-03-2009, 05:36 PM
#37
Rennlist Member
Pins 1 and 3 (i.e., the two outer pins) control the high speed circuit. Are you sure you jumped 1 and 3 -- i.e., the two outer-most pins in the connector? If so, are you sure the fans were in high speed mode?
06-03-2009, 06:59 PM
#39
Instructor
Join Date: Mar 2005
Location: Mesa, AZ
Posts: 215
Likes: 0
Received 0 Likes
on
0 Posts
I have to agree with cruise98. A ground at FS looks like it will trigger the high speed fan. The AC button by itself does not look like it will trigger anything. But rather the refridgerent temp switch is what turns on the fans.
06-04-2009, 01:07 AM
#40
Testing results (losses are one fuse KIA)
Terminal name and active states, all tests with ignition ON.
AC- 12VDC when active, controlled by interior AC switch
Ts- Radiator sensor lower temperature. Active ground
Tf- Radiator sensor upper temperature and AC high pressure switch. Active Ground.
When the AC switch is turned on, with both Ts and Tf inactive, both low fans come one. When Tf is active, then both fans change to high speed.
The problem Chris has could be explained with a double fault. The Upper Rad sensor Tf is stuck at ground and/or the AC input is stuck at 12VDC. This could be confirmed in a couple of minute by pulling the Fan relay and measuring these terminal.
When you turn off the ignition, the fans will continue to run at low speed if Ts is active.
Terminal name and active states, all tests with ignition ON.
AC- 12VDC when active, controlled by interior AC switch
Ts- Radiator sensor lower temperature. Active ground
Tf- Radiator sensor upper temperature and AC high pressure switch. Active Ground.
When the AC switch is turned on, with both Ts and Tf inactive, both low fans come one. When Tf is active, then both fans change to high speed.
The problem Chris has could be explained with a double fault. The Upper Rad sensor Tf is stuck at ground and/or the AC input is stuck at 12VDC. This could be confirmed in a couple of minute by pulling the Fan relay and measuring these terminal.
When you turn off the ignition, the fans will continue to run at low speed if Ts is active.
Last edited by Bri Bro; 06-04-2009 at 03:34 PM.
06-04-2009, 08:59 AM
#41
Rennlist Member
Testing results (losses are one fuse KIA)
Terminal name and active states, all tests with ignition ON.
AC- 12VDC when active, controlled by interior AC switch
Ts- Radiator sensor lower temperature. Active ground
Tf- Radiator sensor upper temperature and AC high pressure switch. Active Ground.
When the AC switch is turned on, with both Ts and Tf inactive, both low fans come one. When Tf is active, then both fans change to high speed.
The problem Chris has could be explained with a double fault. The Upper Rad sensor Tf is stuck at ground and the AC input is stuck at 12VDC. This could be confirmed in a couple of minute by pulling the Fan relay and measuring these terminal.
When you turn off the ignition, the fans will continue to run at low speed if Ts is active.
Terminal name and active states, all tests with ignition ON.
AC- 12VDC when active, controlled by interior AC switch
Ts- Radiator sensor lower temperature. Active ground
Tf- Radiator sensor upper temperature and AC high pressure switch. Active Ground.
When the AC switch is turned on, with both Ts and Tf inactive, both low fans come one. When Tf is active, then both fans change to high speed.
The problem Chris has could be explained with a double fault. The Upper Rad sensor Tf is stuck at ground and the AC input is stuck at 12VDC. This could be confirmed in a couple of minute by pulling the Fan relay and measuring these terminal.
When you turn off the ignition, the fans will continue to run at low speed if Ts is active.
06-04-2009, 09:42 AM
#42
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Thread Starter
06-04-2009, 10:07 AM
#43
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Thread Starter
I think that all that test did was prove that the coolant temp sensor was work as designed.
06-04-2009, 04:04 PM
#44
Rennlist Member
Ahhh... I thought you pulled the connector off the thermo, but if not then Brian's theory works. jumping 1 and 3 is probably not the cause of the low fans, but rather a bad a/c signal. High fans come on with ignition because high thermoswitch is shorted. Try unplugging thermoswitch without jumping anything. If results are the same (no high speed ever, low speed with ignition on) brian may have it.
06-06-2009, 01:59 PM
#45
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Thread Starter
Problem solved - my usual favorite, internal short in harness.
A/C temp circuit was showing a ground but not at the sensor (this shares the high temp fan switch circuit).
Found a 'pinch' in the harness, that fixed it.
Thanks for playing!!!
A/C temp circuit was showing a ground but not at the sensor (this shares the high temp fan switch circuit).
Found a 'pinch' in the harness, that fixed it.
Thanks for playing!!!