thunder52 Posted May 21, 2019 Share Posted May 21, 2019 1998 Outback, 2.5, auto. Neither cooling fan will stay on when commanded, engine hot or cold. Everything I have found when searching is about the fans either not coming ON, or not shutting OFF. They run and cycle with test connectors. They will come on for about 3 seconds when temp reaches ~203F, and/or when a/c is turned on and engaged and then shut off. Have checked all fuses, swapped out all relays (under hood and under dash), swapped 2 wire coolant sensor, and swapped ecu. No joy. All swaps were with known good parts. What would be causing system to lose signal? Also when they start with a/c, there is about a 2 second lag between a/c clutch engaging and fans starting. (Then fans stopping, but clutch still engaged) As an aside, does anyone know what all the cooling relays are called, and what location is which? Service manual says a/c relay in a/c holder, sub-fan 1 in f/b, sub-2, main-1, main-2 in a/c holder. Okay fine, but under hood cover calls all under hood ones "a/c relay". I think I figured out which is which, but confirmation would be helpful. Thanks, Jon Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 21, 2019 Share Posted May 21, 2019 You'll have to pull a diagram and start testing to see what you are losing when they turn off. I can almost guarantee that no one here including myself has ever seen that failure mode. There is about 5 relays and multiple fuses involved as well as the relay control ground signals from the ECU. It's also important to note that these are 2 speed fan motors and they have three wires - two power and one ground. A single power (either one) and ground gives low speed, two powers and ground give high speed - so check that both fans work on both speeds. Could be something weird with the motor windings causing them to stall when they are commanded to high speed. That's a tough one for sure. You will need test equipment to monitor the voltage and voltage drop in various conditions as well as watch ECU live data, etc. GD Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 21, 2019 Author Share Posted May 21, 2019 Thanks for the reply. Yeah, complaints are all for either on, or off. I try to think of the system as mechanical, or electrical. I.E. the a/c test bypasses the sensors, and the ect test uses the sensors. Trying to find the physical link in the diagram for the a/c system to turn on fans, but it only gets me to the mode control with no information on what connects with what inside. Both fans do work on both speeds. I will try disconnecting fans and use test light to see if circuit stays live or not. Don't know if the a/c evap temp sensor comes into play or not. Been poring over the diagrams for a couple of days trying to figure routing. Jon Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted May 21, 2019 Share Posted May 21, 2019 No the system is very simple. When the AC is commanded on, the fans are commanded on through one of their power leads. If the engine coolant temp rises above 204 then the other power lead is switched making them run in high speed if the AC is still on. The AC pressure switch will kick off the AC clutch but the fans will still run as long as the mode selector is in AC or defrost. The functioning of the AC system has nothing to do with the fan operation - even if the AC is inoperative the fans will still run when the mode selector is in an AC or defrost position. GD 1 Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 21, 2019 Author Share Posted May 21, 2019 Thanks. That is the way I figured it. Just can't see the where the a/c switch engages the fan system. Looking for something in that circuit that would interrupt operation. Just tested with engine running and a/c engaged (and stays engaged): Both fans connected- fans cycle Passenger disconnected- driver cycles Driver disconnected- passenger cycles Both disconnected- passenger side has constant hot on yellow/red, no power to drivers side Ground is constant on all tests on both sides. Thanks for taking time to help me. Jon Quote Link to comment Share on other sites More sharing options...
sparkyboy Posted May 23, 2019 Share Posted May 23, 2019 (edited) Maybe try a power probe on the fans to see if they operate properly with a given 12v signal? Then if it were me I would grab a relay and switch and just hardwire the damn things, but I'm geto like that The ecu triggers these via the coolant temp sensor? A fancy scanner will let you trigger the fans through the eco circuit and read what else is going on. They are expensive tho, $1200 for a snap on one used! But an almost invaluable tool for any obd2 diagnosis. Beyond that perhaps find the pin on the ecu and supply that with 12v? But be careful and don't go about that willy nilly! Some circuits get 5 volts and the ecu pin for "fans" might be an out signal to the relay. Good luck man, hope it's an easy fix and be sure to keep us updated! Like GD stated this is a new one! Edited May 23, 2019 by sparkyboy Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 23, 2019 Author Share Posted May 23, 2019 thanks for the come back. Still no luck. I have now also swapped out the fans with other know good. Also for ghits and jiggles I installed NEW ects. All fans, old and new, power up fine. After the fan swap, things changed somewhat: Ignition in run- no fans Start engine a/c on or off- pass fan on Back to RUN-a/c on- pass on, driver on then off Back to RUN-a/c off- pass still on Key off- fan off Rinse, repeat With that one fan running constantly I can't get temp over 184 Battery disconnected overnight, and confirmed green test connectors not connected. Thanks, Jon Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 23, 2019 Author Share Posted May 23, 2019 I might rig something up if it was mine, but this the fishing car for a couple of ladies, (In their 70's) Don't want it to overheat and croak. (The car, not them) Quote Link to comment Share on other sites More sharing options...
sparkyboy Posted May 24, 2019 Share Posted May 24, 2019 (edited) Well cool! Then the fans are off the list. Cts? Might be fooling the ecu into thinking the car is always warm enough to need the main fan. But that would cause hard starting at engine temp cold? And you tried 2 already... Might want to use mechanical gauge or laser temp reader to see if the cts is reading what the actual coolant temp is. Happy wrenching! Edited May 24, 2019 by sparkyboy Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 24, 2019 Author Share Posted May 24, 2019 TA-DA (So fat) Got under the dash to see if any aftermarket stuff was wired to fuse box and found the mirror/lighter fuse was blown. Replaced it and all works! Last test is to reinstall the customer fans and test. Don't know where that system comes into play' Stay tuned for the exciting conclusion. (and what about Mary Ann?) Jon 1 Quote Link to comment Share on other sites More sharing options...
thunder52 Posted May 24, 2019 Author Share Posted May 24, 2019 Half way worked with old fans. Did test ground to: Old fans----Pass to left pin-1.2 ohm -- center pin-0 ohm Driver to left-.5 ohm --center--1.0 ohm known good fans----Pass to left pin- .5 ohm---center-1.0 ohm Driver to left- .5 ohm --center-1.0 ohm Conclusion? Bad fan holding signal to ground, and lighter fuse blown. YMMV Thought I would send this to add to the body of knowledge if it helps. 3 Quote Link to comment Share on other sites More sharing options...
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