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A/C fan when controlling single engine fan via PWM

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Hi all

I have a single Spal 16" Extreme fan which I'm planning to control via PWM.  The main reason for doing so is that this particular fan is rated at 26A but draws significantly higher inrush current when switched on.  The other reason is that the motor is not designed to run at full duty for prolonged periods. Others have reported better performance when using PWM control to have the fan switch on at a lower duty cycle before ramping up at higher engine coolant temperatures.

I can set this up easily enough using a General Purpose PWM output and even map duty in 3D against ECT and road speed. No problems there.

Where I'm stuck is how best to use the same fan as an A/C condensor fan and control it in a similar fashion to the standard Engine Fan output, that is have it trigger whenever the A/C compressor clutch is active, with a suitable time delay to stagger the extra load at idle.

Ideally, I'd want 2 different PWM tables dependant on whether or not A/C clutch is active.

No A/C = engine fan would kick in at around 30% duty at 87-88'C then hit full duty by 92-93'C. Thermostat is rated at 82'C.

With A/C enabled = engine fan would kick in a few seconds after the A/C is active, then run at 30% duty up until 87-88'C, above which it would revert to the no A/C map, ie 30% duty ramping up to fully duty by 92-93'C.

In both scenarios, it would be great if I could have the fan cut out above certain vehicle speeds.

I figure one way to achieve the above is to have a normal GP PWM function for the fan, with the duty cycle mapped against ECT on one axis and A/C Clutch state on the other axis.  I haven't figured out whether this is possible yet, but it would remove the ability to tune fan speed against road speed.

I know the conditions can be set up to only use the GP PWM function when those conditions are met (ie no A/C), but this doesn't appear to allow me to specify a different GP PWM function on the same physical output when different conditions apply (eg A/C enabled, more than 2 seconds has elapsed).

How might this be achieved?

Any help much appreciated.

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I may have figured this out.

Create a Virtual Aux 1 with GP Output function, specifying conditions A/C clutch active for X seconds AND ECT < 87'C

I set the Aux output for the engine fan to GP PWM, specifying conditions Virtual Aux 1 Active OR ECT > 87'C.

Then use something like following table for the GP PWM output:

815368268_GPPWM-enginefan.PNG.8da0b3652e402b8e6b37fa1df41206a5.PNG

If I have this right, when A/C is off, only the areas of the table from ECT > 87'C will be used.

When A/C is off, the areas of the table from ECT < 87'C will be used, allowing me to have the AC fan reduce duty as the vehicle speeds up (where additional condenser airflow is not necessary).

Does this look right?

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If you have any luck PWM this can you let me know. I tried using a 100amp jaycar PWM relay but kept braking the drive pin and flogging out the pin locator. Current In rush from memory is 150 amp so wire it accordingly. 

On my sr20 when it cut in at 100% It droped rev's which could not be dialed out. 

In the end I used a soft starter PWM module to run it. 

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7 hours ago, Ducie54 said:

If you have any luck PWM this can you let me know. I tried using a 100amp jaycar PWM relay but kept braking the drive pin and flogging out the pin locator. Current In rush from memory is 150 amp so wire it accordingly. 

On my sr20 when it cut in at 100% It droped rev's which could not be dialed out. 

In the end I used a soft starter PWM module to run it. 

Thanks. I found your post on HP Academy about this and saw the inrush current graph published by Spal that you posted. That was for the lower power version of mine! 150A was more higher than i was expecting (even if only for a millisecond) and precisely why i want to start it up at low duty.

The Jaycar doesn't have a great rep and can't handle inductive loads, therefore requiring a diode. If you didn't use a diode this is what may have killed it. Or it was just not up to task - i have read plenty of online posts about them not working.

I'm looking at the Haltech HT-030202 which in the past looked the same as one Jaycar used to sell. But it doesn't have any negative reports i can find. Also, its instructions do not mention being unable to drive an inductive load so, although i have not confirmed this with Haltech yet, it *may* not require a diode.

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So any further ideas on whether it is possible to have 2 different 3D PWM tables for engine fan depending on whether or not a condition is met (in this case, specified time after AC clutch is enabled but could equally be AC pressure switch active). 

Otherwise, would my solution work? Ideally it would be nice to have the flexibility to run the fan a bit faster when AC is enabled versus not under certain conditions so 2 different tables would be nice.

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I think your first proposal above should do it fine.  It is usually best to keep things as simple as possible, considering 99% of cars get away with just on/off control for an engine fan you are possibly over thinking it...

If you really want to, depending on how many IO you have spare, you can do a bit of a hack to get a 4D PWM.  A bit hard to explain, but an example below.  You need to use two GP PWM aux outputs.  One controls the fan directly, the other is just wired direct to a digital input.  This Aux we set the DC table to a flat 50%, and instead use the frequency table as our 4D (this is because a DI cant measure DC but can measure frequency).  We use the DI to measure the frequency then put that on the axis of the fan control PWM table.   Set the DI to "GP Speed" with a calibration of 360.  (its reported speed will then match frequency).

Example below, Aux 1 is wired to DI1.  Aux 1 frequency table generates a frequency between 10-100Hz based on road speed and ECT variables.  Aux 2 DC table then has the AC request on one axis and the DI frequency on the other.  You can see in this example my fan would get 20% more DC when air con is on and would still vary with road speed and ECT.

4sGekuG.png

 

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Fantastic! Thanks very much Adam. I had to reread slowly but I understand. I may have scope to do it this way.  As you say,  the other way I proposed (thanks for confirming this is suitable by the way) will likely do the job, but great to know the other option is there if that flexibility is required. I really need to run it on the road and see how much additional airflow is required when AC is on. On my old setup AC pressures would build up unacceptably at low road speeds hence me wanting to get the fan to help, but only to the extent necessary.

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I am doing the same thing using a Mercedes PWM fan controller. The controller has like 8-10awg wires into it stock so it's rated for some good current. I'm running a 14" spal. The corvette uses the same controller put doesn't have the +12v ign signal which may be better with the link system anyway. If the +12v signal is on and the PWM signal is not valid the fan runs 100%.

It's working well so far. 

The fan PWM does need to be inverted so it's 90% duty cycle to be off and 10% duty cycle to run 100%. With the mercedes unit as mentioned above anything below 10 or over 90 and the fan will run 100% speed.

Doesn't really solve the AC issue as I believe most cars don't just bump speed with the AC it usually causes one of the fans to run all the time for airflow over the front core. I think it may almost be better to just have the fun run at 50% minimum if AC is on. Not sure how/if that's doable in the link software scheme though.

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13 hours ago, barge said:

I am doing the same thing using a Mercedes PWM fan controller. The controller has like 8-10awg wires into it stock so it's rated for some good current. I'm running a 14" spal. The corvette uses the same controller put doesn't have the +12v ign signal which may be better with the link system anyway. If the +12v signal is on and the PWM signal is not valid the fan runs 100%.

It's working well so far. 

The fan PWM does need to be inverted so it's 90% duty cycle to be off and 10% duty cycle to run 100%. With the mercedes unit as mentioned above anything below 10 or over 90 and the fan will run 100% speed.

Doesn't really solve the AC issue as I believe most cars don't just bump speed with the AC it usually causes one of the fans to run all the time for airflow over the front core. I think it may almost be better to just have the fun run at 50% minimum if AC is on. Not sure how/if that's doable in the link software scheme though.

 

Thanks very much for the input. I did do some reading on controllers. I read a detailed writeup for my Spal 16" fan on a BMW by using a Volvo fan controller. I believe the Corvette controller is designed for use with a brushless Spal fan and so may not be appropriate for a conventional brushed motor.

I'm going to try with a solid state relay first, as that is the cheapest, neatest and most configurable option. But I'll keep in mind the possibility of a separate controller.

I can do 50% duty with A/C enabled using both strategies referred to in the above posts (mine and Adam's). I came up with 30% as a random guess at what will be needed. It only requires a small amount of additional airflow to bring A/C gas pressures back down and only when vehicle is stationary or at very low road speeds.  More cooling might be required on hotter days where the compressor is working harder, in which case I might enable the A/C fan by A/C pressure switch instead of A/C compressor clutch.  That way the fan would kick in whenever pressure climbs and will remain on until pressure reduces below the switch point.

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The very newest Corvettes may use brushless fans but the controller i'm using is for a normal brushed fan.

https://rennlist.com/forums/928-forum/917865-mercedes-or-corvette-pwm-cooling-fan-controller-info.html

This is a pretty good overview of the controller i'm using. I was able to source the pins for it and reused the connector housing i got with the one i bought.

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On 7/14/2019 at 8:52 AM, Ducie54 said:

If you have any luck PWM this can you let me know. I tried using a 100amp jaycar PWM relay but kept braking the drive pin and flogging out the pin locator. Current In rush from memory is 150 amp so wire it accordingly. 

On my sr20 when it cut in at 100% It droped rev's which could not be dialed out. 

In the end I used a soft starter PWM module to run it. 

Following up on the above post, the Haltech tech guys have confirmed their solid state relay is sourced from the same supplier as Jaycar and is potentially susceptible to damage when driving inductive loads without flyback suppression. They do not show the flyback diode in the wiring diagram however. Also, Haltech's published wiring diagram differs from the wiring diagrams you posted in this thread, which don't look right to me: 

I have had a go at amending how I think the SSR should be wired based on the latest revision of Haltech's installation manual for its SSR and posted in that thread.

Alternatively, if the SSR option doesn't work, I'll probably end up using the Corvette C6 fan controller or similar OEM solution as barge suggested.

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