-----Original Message----- From: 928 SPECIALISTS [mailto:p928sp@928gt.com] Sent: Wednesday, June 23, 1999 8:33 PM To: 928 Subject: [928] Cooling fan operation CONTEST !!! S4/GT/GTS Cooling Fan Myths and Mysteries Contest !! First person to post to the Rennlist the correct answers for the following questions wins a free 928SP HeatShield windshield sun reflector. All questions are if the system is working as designed. (A) Fans will come on when A/C system (if it is working) is active with ignition switch on, hood open or closed. True X or False _ (B) Fans will come on when engine coolant reaches a certain temp (speed of each fan increases with temp) with ignition switch on, hood open or closed. True X or False _ (C) Fans will run when intake reaches a certain temp and will continue to run until temp is reduced below intake temp switch threshold, ignition switch off (key in or out of switch) and hood closed. True X or False _ ;-) David Roberts 928 SPECIALISTS Phone: (770) 928-4777 Fax: (770) 592-4608 Website: http://www.928GT.com E-Mail: 928@928GT.com From: Jim [jim@928intl.com] Sent: Tuesday, July 18, 2000 11:32 AM To: 928 Subject: [928] RE: All Fans Run All The Time 87 928 S4 When the intake temp sensor 928 606 217 00- thermo switch-- middle of the plenum somewhat to the rear fails the cooling fans can run all the time - one possible cause of this problem in a very complicated engine cooling management system . Jim Bailey 928 International jim@928intl.com 79 928 5spd 80 928 5spd 68 911 5spd From: Wally Plumley [wplumley@avana.net] Sent: Thursday, August 10, 2000 8:46 PM To: Pirtle, John Subject: RE: [928] no fan run-on At 07:06 AM 8/10/00 -0400, you wrote: >I keep thinking this and I hope you're right, but is it normal for them to >run-on with the key in one of the ignition positions? Yes, it is. Wally From: Dr. Bob [dr.bobf@worldnet.att.net] Sent: Thursday, December 28, 2000 11:14 AM To: 928 Subject: [928] re: .../rad. fan funny business David R. Hendrickson wrote to the list: > >[rule #1 :) 88 S4 AT - 106k miles] > > >on another note, in the two months that i've had the car, the fans don't >run after shutting off the engine unless i turn the key back on to power >them. they'd run for a minute or two then shut off. the last couple days >the fans have been running for about 5+ minutes in a fast/slow cycle. the >tech at the shop today noticed that the driver side fan is not running at >all now (i know that it was working previously). the A/C pump is seized, >so i'd guess there's zero freon pressure. now Wally told me which sensors >the fan system looks at (inlet air temp, water temp and freon press.), but >would a sensor reading or the fan brain (r/h side of hood latch or under >the pass seat side box?) kill one fan? (controlled individually?) or is >the fan dead? the wire plug feels firmly in place. i suspect the longer >running time and fast/slow running of the single fan is it trying to make >up for the lost additional cooling ability of the dead one. i'm prob'ly >forgetting something here... Start off with the simple stuff on the fan motor. There are individual fuses for the fan motors, so check both to make sure they are OK before you dig any deeper. If both fuses are OK, try swapping the wire leads at the motors and see if the previously dead fan springs to life. If it doesn't, it's probably the fan motor. If it does, go back to the controller output unit on the front apron. That output unit receives a speed signal from the controller, both output transistors receive the same signal. Therefore, if one fan is running and the other is off, you can eliminate any upstream controls and focus on the output unit itself and the wiring between it and the fan motor. The output unit features a pair of FET-type transistors that switch the DC power on and off for the fans. Speed is varied by swithing them on and off quickly, with slow speeds having less "on" time compared to faster speeds, and finally high speed that is "on" all the time. A capable lister in Europe wrote about disecting the controller and replacing the FET stages successfully; the components are marked with industry numbers and may be available locally to you. Alternatively, replacements are available from 928 International, 928 Specialists, and Devek in both new and used flavors. As far as the fan(s) running after engine shutoff-- Only on the hottest days after a hard uphill pull have the fans stayed on in my '89 after key off. "Normal" operation has the fans off a second or two after key off. So, look at what has changed to help diagnose the change in operation of the fans. Your shop did a clean-and wash of the top section of the engine where the temp sensor-II is located. That's the sensor that manages fan run after key off. They also did a coolant replace, which may or may not have included an adequate 'burp' to get any remaining air out of that high spot in the intake manifold where the sensor sits. The sensor is a reverse-resistance type, where the resistance of the sensor actually rises as the temp goes up. Start off by removing the two electrical connector at the sensor, and cleaning the contacts on the end of the cable as well as the tabs on the sensor itself. Replace the connector on the sensor and give it a try. Burping the coolant system is a task that involves bleeding air out of the high spots. I won't go into details, but will state that both the dealer and the doctor have 'burped' my car after coolant services, and both times the reservoir bottle needed a pint or so of additional coolant after a week of driving. I thought I had a fool-proof plan when I did it, and still it had a bit of air in it I guess. Anyway, look to see that the reservoir has sufficient coolant in it. My low-level light gave a warning after the dealer did it at purchase; when I did it, it wasn't low enough to turn the light on but still took a little to top it up. Hope this helps! With luck, a fuse will get replaced and all will be well once again! dr bob From: Wally Plumley [wplumley@bellsouth.net] Sent: Wednesday, March 21, 2001 10:24 PM To: 928 Subject: [928] Re: Installation of Aftermarket fan At 08:53 PM 3/21/01, August Spillers wrote: >Installed Rapid Cool fan on my 81. > >Question: After connecting the wires back up, when should the fan start? >I know it's supposed to start after 90 C; right? But what if it does'nt >start? I checked the fuse #16, put in a new 25 just in case. Is the >relay that is described as the AC fan applicable to the electric fan? In >the event that there is no power coming through these wires for whatever >reason; is there an alternate area. I tried two wires coming off what >looked like a compressor up front but nothing besides minor sparking. If you simply replaced the existing electric fan with the new one, the fan will be operated by the fan relay (XVIII). The operating coil of this relay receives power from relay X on terminal 86, so the coil gets power anytime the ignition switch is on. The ground side of the coil (terminal 85) is connected to the freon temp switch, located on the top of the receiver/dryer in front of the radiator. When the freon gets hot, this switch closes, powering the relay coil, closing the relay contacts, powering the fan. In addition, terminal 85 is connected to the temp switch located in the forward face of the radiator, low on the left side. When the coolant gets hot, this switch closes, powering the coil, closing the contacts, powering the fan. If you pull the connector from the top switch on the receiver/dryer and short the terminals in the harness, the fan should run (ignition switch on). Likewise, if you pull the connector from the radiator switch and short the contacts in the harness. If not, pull the fan relay XVIII, and jumper terminals 30 and 87 in the socket. The fan should run. If not, you have a problem with the fuse or the wiring. If the fan runs with 30 and 87 jumpered, but not with the switches jumpered, the relay is probably bad. Wally Plumley 928 Specialists From: Wally Plumley [wplumley@bellsouth.net] Sent: Monday, October 15, 2001 11:31 PM To: 928 Subject: [928] Re: '89S4 Cooling Flap Problems and Questions There are three sensors for the fans/flaps: Coolant temp sensor - located in the lower left forward face of the radiator (Sounds as if this one might be your problem). Freon temp sensor - located on top of the receiver/dryer. Inlet air temp sensor - located on top of the manifold - mainly used for cool-down after shut-down. If the fans are off, the flaps should be 0% open (closed). If the fans are running at low speed, the flaps should be 30% open. If the fans are running at high speed, the flaps should be 100% open. If the coolant is hot (over 85 deg C), the fans should be on full speed and the flaps should be fully open. Sounds as if there may be a problem with your coolant temp switch. Wally Plumley 928 Specialists From: Wally Plumley [wplumley@bellsouth.net] Sent: Tuesday, October 16, 2001 9:02 AM To: 928 Subject: [928] Re: '89S4 Cooling Flap Problems and Questions At 05:46 AM 10/16/01, rodlonsdale2 wrote: >I have a problem with my flaps on my late 89 S4 (first of the digi-dash) >in UK although the sequence is different. My flaps and fans appear to >work satisfactorily as long as the A/C is off. Having said that I will >check the sequence now I have read Wally's note as well as the two >references from Darren. As soon as I switch on the A/C, which in itself >seems to work OK, the flaps shut although the fans continue to run. They >shut sufficiently quickly that I cannot get from leaning into the car, >to operate the A/C switch, back to the engine compartment to see them >close. Could this be the the freon temperature sensor? Definitely not the proper mode of operation. The next test probably should be at the control box, which is located between the passenger seat and the door. I have a problem here - I don't know how the box is oriented on a RHD car. There are two plugs, identified as I and II. If you look down upon the box, with the part number visible at the top and the plugs at the bottom, the left plug is I and the right plug is II. If you hold the disconnected plug so that you are looking at the connectors with the wire harness coming out at the top, pin 1 is bottom left, with 1, 3, 5, 7 going up the left side, 2, 4, 6, 8 up the right side. There should be a dot between 1 and 2. To test the freon sender: Connect an ohmmeter between pin 4 of plug II and pin 7 of plug I and test the resistance with the A/C running. 1.5 bar - 22 */- 4 ohm 5 bar - 53 */- 4 ohm 10 bar - 92 */- 5 ohm 15 bar - 125 */- 5 ohm I doubt that the problem is the sender. Unless you have ready access to a set of A/C gauges, I would suggest that you just check the resistance with the A/C running, and see if you get 20 - 50 ohms at idle, and that the resistance increases slightly when you increase engine RPM and hold it for a moment. To test the flap motor: Use a jumper wire to connect pins 5 and 7 of plug I for four seconds. The flaps should be closed. Connect pin 2 of plug II to pin 7 of plug I for four seconds. The flaps should move to the 30% position. Connect pins 7 and 1 of plug I for four seconds. The flaps should move to the 100% open position. If the flap motor does not perform as specified, check the wire harness between the plugs and the motor. If it is good, the flap motor may be bad. If all of this works correctly, the control unit may be bad. >My current temporary solution has been to disconnect the link from the >motor to the flaps leaving the flaps continually open and all seems >well. However I would like to reinstate them and would welcome any >comments. The only problem that I have noticed is a small tear in the >boot that covers the motor and one task this winter is to take the motor >off to see if the has been any water damage. > From Wally's notes it appears that the motor operation has three stages >- closed, 30% open and fully open or are these just particular positions >to illustrate measuring points on a smoothly variable opening motion? These appear to be fixed positions. 0% is closed, 30% is about 10 mm (memory here - don't take this as an exact spec), 100% is wide open. >When the flaps are 30% open I presume that the vanes are turned 30% >which is not necessary the air flow being 30% (or is it ?). >Interestingly this problem has been with the car since purchase but >disguised by other A/C problems that were solved by cleaning up the >outside air temp sensor in the cooling duct to the alternator. The >engine temperature is constant at one needle width below the second >white graduation without the A/C on and flaps connected, and with A/C on >and flaps disconnected. However with A/C on and flaps connected the >temperature creeps up and, on a warm day (we have them occasionally!), >it will get to nearly the red mark but has never gone to it. It also >seems that switching the A/C off does not open the flaps but stopping >and shutting off does reinstate the normal operation when the A/C is >off. Can't help but be impressed with the system that still has >sufficient cooling on a warm day (for UK that is) with the flaps shut to >prevent real overheating. >Any further comments Wally? Your input is read fanatically here and is >much appreciated. Rod Thanks. Good luck! Wally Plumley 928 Specialists