KYPREO

Thanks Adam. The IN4004 has an average forward current rating of 1A but a non-repetitive forward surge current rating of 30A. When used as a flyback diode, I imagine current wouldn't be flowing through the diode long enough for the forward average current to matter much..it's more the temporary spike from the inductive discharge from the motor when switched off between cycles? Assuming that is correct, the 30A is still probably insufficient for my particular application. While enough for my fan at full load (~26A) is not enough for inrush current, which is around 5x that, so the diode should be able to handle 150A to be on the safe side. You can get fast switching Schottky rectifiers in the DO-201AD size with 5A forward current rating and up to 220A non-repetitive forward surge current rating. Something like Vishay SB-560 which is rated at 60V and 220A and looks quite cheap. The Schottky rectifier is probably more suitable to high frequency switching than the 1N400x diodes anyway. The D0-201AD package is the style of diode recommended by Power-Io who makes high current solid state relays for DC usage (see https://www.power-io.com/products/hdd.htm) Any thoughts appreciated

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.

Bumping this thread. The Haltech SSR is essentially the same as the Jaycar relay listed above. It does not have an internal flyback suppression and so will need a diode to be fitted across the load if the device uses a bit of current (like a fan). Also, Haltech latest revision of the instruction manual shows a different wiring diagram for ground switching a device than those listed above, with the +ve terminal of the load wired directly to battery +ve (although I think this should have a fuse), and the +3 terminal of the SSR connected to switched ignition +ve (which I think should come from the relay output after the main ECU relay so as to avoid backfeeding). Unlike the Haltech, the Link does not need a pullup resistor across the SSR. Based on the above factors, I am thinking the wiring for the Jaycar/Haltech SSR on a Link should look something like this (with flyback diode, eg 1N4004, wired across the load):

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.

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.

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.

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.

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: 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?

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.