bobsblue95
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Post by bobsblue95 on Apr 6, 2012 16:31:08 GMT -6
With all due respect to Randy T., driving around with a "Low Coolant" warning all the time would make me crazy paranoid! So I decided to do a more "politically correct" mod. With a few simple wiring changes, my fans will now run at low speed whenever the key is in RUN, and at high speed whenever the low speed relay used to kick in.  Here's how... Open up the passenger side kick panel to access the PCM. Unplug the BLUE connector and find F7 and F8 as shown. (Note for 96 and later, the connector is different as Sall points out below. Same idea, but pins 32 and 33)  Use a 1/16" allen wrench to remove the blue and green wires from the connector (again, not sure if this works on the later connector.) Just push it into the larger opening on the face of the connector and the terminal should release. Don't pull hard. If you have to pull hard, it's not released.Insert the Blue wire where the Green wire used to be. This makes the Low speed setting run the fans at High speed.  Connect the Green wire to ground (I attached it to the PCM housing.) This turns the Low speed relay on ALL the time (even key off.) We need to remove [Hot at all times] 12v from the relay and replace it with [Hot in Run] 12v... For this part, you may want to remove the Ignition Module for clearance. Locate the three relays on the firewall. The right ( passenger side!) relay is the low speed fan relay. The middle relay is the main ABS relay. Pull BOTH straight up to remove them from the bracket, then unplug them and set the relays aside for now. On the low speed fan socket, locate the ORANGE wire and cut it as FAR from the relay socket as you can. This orange wire from the fan relay needs to be spliced into the ABS main relay BROWN wire. A scotchlock should work, but I chose to solder mine. I don't like seeing scotchlocks under my hood. That's it! The brown wire provides 12v only at key on, so the low speed fans turn off with the key. If you're wondering if running the fans all the time will make them fail sooner... probably (although at low speed, not appreciably, IMO.) But I'd gladly sacrifice two cooling fan motors to keep an Aurora engine alive longer! Cheers, Bob *UPDATE* I found this circuit that should work for manual adjustment of low-speed fan setting. This circuit works by supplementing, not bypassing the PCM, so the PCM can still command the fans as it normally would. You adjust potentiometer R4 to turn the fans on at any temp you like. This mod *will* run the fans after they key is turned off, until the temp drops below the set level.  Basically you replace the light bulb with the low speed cooling fan relay. R1 may need to be adjusted to limit current through transistor Q1. I'll build one and figure out the needed tweaks. |
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Post by sall on Apr 6, 2012 17:53:26 GMT -6
Good stuff! Should be a little different on '96-'99 PCM though, but same idea can be used.
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bobsblue95
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Post by bobsblue95 on Apr 6, 2012 21:32:51 GMT -6
Well if someone with a 96-99 can check the schematic for the cooling fans and see which pins are used for high and low speed relay control, that'd be great. I think I'd be surprised if they are different though. Note that even with the FSM, as you can see in the first pic, I verified continuity to the relay before proceeding. My other idea was a manual switch that would let me select high or low speed at will, but I like this "automatic" solution better. On a side note, every time I look at the fuse box labels and see CLNG FAN, for some reason I keep thinking there must have been a Ceiling Fan option that I didn't get!  |
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Post by sall on Apr 7, 2012 7:41:16 GMT -6
The pins differ on the '96-'99 as connector is different. Here are those pins on '96-'99 PCM: PCM C2 Connector:  everything else looks as if it is the same:  May prevent proper warm up[time] in winter with fan always on but can't verify. I like the idea of manual switch. I have four spare relays on the CarPC. Hmm. Regardless excellent idea. I wonder if the fans are simply dual speed or if can use a PWM for complete variable speed based on temp... |
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Post by nelson480 on Apr 7, 2012 8:14:03 GMT -6
This is a cool idea robert! But its easier for me to just run the A/C. That runs the fans and keeps it right at 200 in bumper to bumper ;D
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bobsblue95
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Post by bobsblue95 on Apr 7, 2012 9:48:21 GMT -6
Sall, they are just DC motors. Just vary the voltage. The low speed is accomplished by running them in series instead of parallel. I suppose PWM could work though.
I don't think warmup will be a problem. There is still a thermostat. I suppose it will operate a little more frequently now, but again, a fair trade-off.
With your car pc I suppose you could write a plugin(?) to monitor the coolant temp and control the fan speed accordingly. You'd have to totally bypass the relays and use heavy duty triacs for PWM (maybe a blower motor controller?) I'd just have it control the original relays.
Dan, that reminds me... I gotta overhaul my A/C, and soon! Gotta do the works, including one of the blend door actuators.
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Post by wireless on Apr 7, 2012 13:10:40 GMT -6
Dan, that reminds me... I gotta overhaul my A/C, and soon! Me too! It's starting to heat up here rather quickly.. I'm considering doing this, but not set on it yet! |
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Post by aba1987 on Apr 7, 2012 13:54:35 GMT -6
Dan, that reminds me... I gotta overhaul my A/C, and soon! Me too! It's starting to heat up here rather quickly.. I'm considering doing this, but not set on it yet! I wanna do it too. Kinda at limbo. |
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Post by sall on Jun 3, 2012 18:21:57 GMT -6
How is this working out for you in the TX heat now, Bob? This deserves a sticky too!
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bobsblue95
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Post by bobsblue95 on Jun 4, 2012 7:22:18 GMT -6
I haven't had any problems, she holds steady around 220, maybe 230 if I'm stopped for a long time on a hot day, and drops below 220 as soon as I start moving. Before the mod it would get up around 240 before I'd hear the high speed fans kick in and it always made me nervous. It seems as though the water pump doesn't quite push enough volume at idle.
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Randy T.
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Post by Randy T. on Jun 9, 2012 6:34:12 GMT -6
Awesome Bob! Thanks. I am going to have to tackle this sometime, if I do I will get some more pics to add. DING DING*** LOW COOLANT...... lol. How hard would it be to keep the fans running after you shut the car off? Just a minute or two would be fine. I love it when I turn my Aurora off because when the fans slow down they have a jet sound to them. *Stickied, thanks again Bob. Your Aurora is running a little hot for my taste, pull your thermostat, mine runs around 175-200 and still has good heat in the winter.
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Post by sall on Jun 9, 2012 8:04:21 GMT -6
How hard would it be to keep the fans running after you shut the car off? Just a minute or two would be fine. I am currently kicking something up using a microcontroller to do this and had that option in mind. The PCM will actually do this but not unless the coolant temperature is above 300*F IIRC. Way too high for my taste. With no coolant actually circulating though I am not sure it does much good? Haha good opportunity for electric water pump then you could keep circulation while still cooling. Anyways, mine probably won't be done for awhile, but will use the ECT sensor resistance to turn on/off low/high the fan relays via microcontroller. I don't need/want the fans running at all times just to lower the factory on/off temps. This module will basically bypass the PCM altogether with an extra input for when AC is commanded. |
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Post by nelson480 on Jun 9, 2012 10:42:06 GMT -6
How hard would it be to keep the fans running after you shut the car off? Just a minute or two would be fine. I am currently kicking something up using a microcontroller to do this and had that option in mind. The PCM will actually do this but not unless the coolant temperature is above 300*F IIRC. Way too high for my taste. With no coolant actually circulating though I am not sure it does much good? Haha good opportunity for electric water pump then you could keep circulation while still cooling. 300 degrees? This engine would be locked up at that temp Anyways, mine probably won't be done for awhile, but will use the ECT sensor resistance to turn on/off low/high the fan relays via microcontroller. I don't need/want the fans running at all times just to lower the factory on/off temps. This module will basically bypass the PCM altogether with an extra input for when AC is commanded. |
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Post by sall on Jun 9, 2012 13:16:24 GMT -6
Kid you not brother. Talk to the engineers lol. That's why this mod is 'optimal' haha.  |
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Post by nelson480 on Jun 9, 2012 13:56:26 GMT -6
That is insane. The engine would be done at that temperature.
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XJSman89
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Post by XJSman89 on Jun 9, 2012 23:07:36 GMT -6
That is probably to prevent heat soak... It is possible that it would soak to that temp if it was at like 280 when you turned the car off. I would like to be able to do this as well to cool it off, I need to figure out the turbo mode option on my alarm so that I can let it run for a couple minutes after parking the car by pressing a button. It is meant to let a turbo cool off if you've been running it hard. The option is there, just haven't configured it.
Great writeup, bob!
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Post by nelson480 on Jun 10, 2012 0:38:12 GMT -6
Isn't it on 4cyl mode at 260?
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bobsblue95
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Post by bobsblue95 on Jun 10, 2012 22:36:11 GMT -6
How hard would it be to keep the fans running after you shut the car off? Just a minute or two would be fine. I am currently kicking something up using a microcontroller to do this and had that option in mind. I found a really simple circuit (less than $5 to build) that will allow you to set your own low-temp fan setting, retain original PCM fan functions, and keep the fans running after key-off until the preset temp is reached. (added to the end of the first post) |
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Post by sall on Jun 11, 2012 6:03:35 GMT -6
I am currently kicking something up using a microcontroller to do this and had that option in mind. I found a really simple circuit (less than $5 to build) that will allow you to set your own low-temp fan setting, retain original PCM fan functions, and keep the fans running after key-off until the preset temp is reached. (added to the end of the first post) Nice little circuit. I would prefer much like your original post to control both high and low at different temps than the PCM setting though. The microcontroller program board/two microcontrollers is $4.30 shipped. I have like ten of them though plus like 50 various microprocessors lol. I'm certain I have everything for the circuit you posted to test on a breadboard. I can understand some would not want to bypass the PCM altogether but for what I would like to do I really see no way around it(other than $300 tune for a mod you can do with $5 worth of parts lol). Unless you can have mod the ECT to falsely report temp but then it would throw the gauge off... dangerous  . And Collins... for that turbo cool down function on your remote start, I would say run that wire directly to the low speed cooling fan relay trigger with a diode inline and a diode on the low speed fan relay relay trigger from the PCM to the relay to prevent back feed. As I mentioned earlier though I'm not sure leaving the fans on will do much good but it may help as there is no coolant circulating. |
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Randy T.
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Post by Randy T. on Jun 11, 2012 6:22:32 GMT -6
As I mentioned earlier though I'm not sure leaving the fans on will do much good but it may help as there is no coolant circulating. That's what I was thinking after I had mentioned it. |
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bobsblue95
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Post by bobsblue95 on Jun 11, 2012 7:06:47 GMT -6
I found a really simple circuit (less than $5 to build) that will allow you to set your own low-temp fan setting, retain original PCM fan functions, and keep the fans running after key-off until the preset temp is reached. (added to the end of the first post) Nice little circuit. I would prefer much like your original post to control both high and low at different temps than the PCM setting though. The microcontroller program board/two microcontrollers is $4.30 shipped. I have like ten of them though plus like 50 various microprocessors lol. I'm certain I have everything for the circuit you posted to test on a breadboard. In my case I plan to keep the high speed fan connected to the low speed output and use this circuit to turn low speed on/off instead of it running full time. The PCM turns on the low speed output any time it calls for the high speed output, so no worries, it will still kick the fans on (high only) whenever it would have before. It would be trivial to double this circuit for dual adjustable temp settings though. The PCM cooling fan outputs are "active low" meaning they connect ground to the relay to activate it, not 12v. As long as your remote start cool down function does the same, you don't need to worry about isolation diodes or anything, a splice will be fine. The fan relays have constant power, so *any* time the control pin gets grounded, the fans run. It's perfectly safe to apply ground to the inactive PCM fan lines as they are in a state of high impedance when off, basically already diode protected internally. If your cool down wire provides power instead of ground, just have it drive a relay that connects the low speed relay to ground. Sall, can't you use your carputer to monitor ECT and drive one or two of your relays to do this job? Seems like a microcontroller for this task is overkill, even on the Aurora lol. |
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Post by sall on Jun 11, 2012 9:52:57 GMT -6
The microcontroller would be less components. Only additional components would be small voltage regulator and a pot to set the on/off temp. It's also good practice for coding(for myself at least). I will explore some analog circuits further or possibly use two of the circuit you posted and make them talk to each other. I posted a brief question on another forum for some input or insight on additional circuits.
I could in theory write a plugin to make the OBDII and Relay App talk to each other but I don't fully trust the CarPC to take on this task. Too many variables for failure. Partially the reason I have not switched to digital gauge cluster overlay.
lol and yeah I should take the time to look at the schematics again. If Collins only outputs a high then he could use a relay like you said or a transistor to switch it low. But as we discussed it's really only going to further cool the coolant in the radiator, it's not circulating. Remote electric water pump install? Now that's overkill haha.
Do you by chance have the temperature/resistance chart handy for the ECT sensor, Bob?
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Post by poofables on Jun 11, 2012 11:15:55 GMT -6
How hard would it be to keep the fans running after you shut the car off? Just a minute or two would be fine. I am currently kicking something up using a microcontroller to do this and had that option in mind. The PCM will actually do this but not unless the coolant temperature is above 300*F IIRC. Way too high for my taste. With no coolant actually circulating though I am not sure it does much good? Haha good opportunity for electric water pump then you could keep circulation while still cooling. Anyways, mine probably won't be done for awhile, but will use the ECT sensor resistance to turn on/off low/high the fan relays via microcontroller. I don't need/want the fans running at all times just to lower the factory on/off temps. This module will basically bypass the PCM altogether with an extra input for when AC is commanded. When I replaced the clutch fan in my jeep with an electric fan, I used a fan relay with a temperature sensor. Drill and tap thermostat housing and thread the sensor in there. then you can adjust when the fan comes on and off based on temperature. It will continue to run after the engine is off as it is on constant hot. You could do this with the fans and electric water pump if you wanted them to run after the engine is off. |
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Post by sall on Jun 11, 2012 11:21:06 GMT -6
lol Okay. I think I can simplify this for those like myself not wanting fans on at all times. Forget everything lol. Use the circuits you posted(or equivalent) to set your desired low speed temp on/off and just do the pin swap on the PCM like the write-up. I am pretty sure those parts can handle the vehicle voltage, but will look a the datasheet. I think a TVS or other protection would be a good idea as well, but not exactly necessary. Does this sound feasible. I'm a bit tired today haha. Still brainstorming. Poofables, no sense in adding another ETC as we will utilize the current one. I think I am slowly changin my mind about the MC. Found 'em:  Do you think a good temp to turn the low on is about 205-210*F? Highs kick on at OEM low temp of 229*F. |
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bobsblue95
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Post by bobsblue95 on Jun 12, 2012 21:34:15 GMT -6
haha right! I was thinking along similar lines, plus the benefit of having spare fan motors in my inventory is kinda nice.
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Post by shelbyracing on Jun 14, 2012 17:43:37 GMT -6
This should be stickied to performance mods under cooling.  This is some good stuff man, how about only on when car is running? What could we splice in to for that, Fuel pump ground and leave hot wire alone? |
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bobsblue95
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Post by bobsblue95 on Jun 14, 2012 20:58:17 GMT -6
This should be stickied to performance mods under cooling. This is some good stuff man, how about only on when car is running? What could we splice in to for that, Fuel pump ground and leave hot wire alone? Hmm, that's a thought. I'll look at the fuel pump schematic and see. Might take a long run of wire to reach the rear relay center or pcm though. |
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Post by shelbyracing on Jun 15, 2012 12:13:32 GMT -6
If I knew which wire it was @ pcm I'd be doing this right now  Shouldn't there be a wire running from pcm to rear? I was thinking about taking low speed and connecting it right in to the fuel pump wire. It would be a lot of probing so I'll be lazy and wait for your revealing of the magic wire lol  Even if I have to fish it through to the rear shouldn't need but 16 or smaller gauge I want to get a service manual badly but as everything else $$$.....  |
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Post by shelbyracing on Jul 26, 2012 20:40:45 GMT -6
Okay so I've looked at it and the fuel pump is constant ground and most everything  so I took a different approach. I installed a probe above my radiator between the fins. I have it adjusted to a bout 180-185 degrees. It was only 20 bucks at advance and the knob is above my overflow tank barely. The pressure switch circuitry is connected to the low speed fan control out of pcm and other end is grounded. Then the high speed is in low speed place. Now my fans run on low anytime my radiator is around 180 degrees and run until it is down to 180 regardless of key on/off. ;D |
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98aurora
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Post by 98aurora on Jul 28, 2012 17:22:16 GMT -6
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Here's how...
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This is some good stuff man, how about only on when car is running? What could we splice in to for that, Fuel pump ground and leave hot wire alone?
Shouldn't there be a wire running from pcm to rear? I was thinking about taking low speed and connecting it right in to the fuel pump wire. It would be a lot of probing so I'll be lazy and wait for your revealing of the magic wire lol 
Even if I have to fish it through to the rear shouldn't need but 16 or smaller gauge 
so I took a different approach. 