Fan Control Eunos 1.6 1990
 

Hi Just be reading how to install MS 1 V3 on my 1990 1.6 Eunos and the following I just do not understand wher it says " Jump the flat side of your middle Led to your harness " so can some one explain.

Now I just broke off the legs of my Q7 to fit Q4 and checking the part numbers I find Q4 and Q7 are exactly the same PN2222A so what am I missing here, again any help appreciated, Thanks DM

(Simply swap Q7 for Q4, and jump the flat side of the middle LED to your harness. That's it. Under the software you'll enable the middle LED circuit to use Output 4 and then turn output to drive the fan control.)

Q7 is normally a 2N3904, rated at 200mA only. That's why it is suggested to replace it with Q4, which is a normally a ZTX450, rated at 1A.
If you already got a PN2222/2N2222 (rated at 800mA) than that's fine as well. IIRC the fan relay draws under 500mA.

The flat side of the middle led (D15) is the long leg (iow, the upper hole). Simply solder a wire to that pin and that wire is your output to activate the fan.
Do not forget to add a 1N4001 diode. Solder it with the banded side to a 12V source (like S12 for example) and the other end to the fan output. This will prevent flyback currents to damage the circuit.

If you have A/C, I suggest letting the thermosensor control the fan. It activates at 97°C.
Use D15 to activate the A/C fan instead, at say 100°C. That way it'll provide extra cooling when needed.

See also 90-93 MS2 non-sequential | Frank's Westfield MX5 90-93 MS2 non-sequential |

Hi Frank, Thanks a lot, I should have checked the part number before I broke all its legs off so now I will have to get them out and refit same, I wonder why it never said anything about fitting the IN4001 diode as well ? I suppose if you are an Electronics expert then it would be obvious but for a newb like me all steps must be spelled out, so anyway many Thanks for all you help, I have another Thread running on here trying to get some help with my install as I just can not get any RPM on Stim or TS on car, I will checkout you Westfield MX5 links and see if it helps me, so again Thanks, Regards DM

Basically, every output that activates a coil (thus a solenoid or a relay) needs a flyback diode. Once you remove power from a coil, that coil will generate a (high) current in the opposite direction (flyback current).
So, your fuel pump output, fan output, boost control output, idle output etc all need a diodes to redirect that current back to the 12V source, away from the Megasquirt circuits. If you don't add the diodes it's very likely that something gets burned out.

Hi Frank, Thanks again, what a clear precise explanation soon I will be an expert as well, Regards DM

Hi Frank Thanks again, now got my Fan circuit built as you explained, so now and the bad news is as I now have my Megasquirt all finished as per info on here and made my adapter loom to connect direct to MX5 loom and DB37 MS plug, fitted my Motor Bike TPS which uses same plug as Original just had to swap 2 of the wires about so that is all calibrated on MS in TunerStudio, Fuel Pump primes when I switch on, but when I am cranking I am not getting any RPM in Tuner Studio and so no spark at plugs ??, now I have a spark plug stuffed up No1 lead and earthed so I can see if it is sparking when cranking and only time I see just one spark is when I first switch on, so at least that must show my spark circuits are all correct so all I am missing is the RPM,( I know there is a Mod to cure this problem which I will do once I get my engine running) as you can imagine I have been over and over all my mods and wiring several times even sent messages to DIYautotune asking for some help but I suppose they are too busy to be helping me, so if can think of any tests etc I can do to verify my mods please let me know as any help is better than none, Thanks, Regards DM

correct me if i'm wrong here but i have always thought the diode is placed with the band on the output side of the transistor and the other side to ground. so for example a relay coil the diode will be blocking in normal on mode and then allow the reverse voltage as the coil powers down??