pin 30 (pwm idle ) always grounded

[rich454mc]

Hi. I'm running ms2 v3.00 firware 2.92. assembled it myself. using pin 30 to control cooling fan relay. about 30 minutes after hooking everything up my cooling fans came on by themselves. after checking wiring, found pin 30 was always grounded even with power disconnected to ms2. if I disconnect the main ms2 connector, it shuts off. i'm sure its a board issue but I don't know where to look. thanks in advance.

[DonTZ125]

Please post up your .msq tune file so we can take a look at it.

[rich454mc]

here you go .

CurrentTune.msq

[trakkies]

Hi. I'm running ms2 v3.00 firware 2.92. assembled it myself. using pin 30 to control cooling fan relay. about 30 minutes after hooking everything up my cooling fans came on by themselves. after checking wiring, found pin 30 was always grounded even with power disconnected to ms2. if I disconnect the main ms2 connector, it shuts off. i'm sure its a board issue but I don't know where to look. thanks in advance.

With the power off, remove the daughter board. Power up and see if the fan runs. If it does, you've got a fault in the driver circuit. It's not common, but I've known a ZTX 450 to fail short circuit. Or you could have a solder bridge at Q4 or Q20 - the PCB pads are very close together. Examine with a magnifying glass.

[rich454mc]

I have done what you said and it is still grounded. I checked q20 and q4 and sure enough q4 was bridged. Thanks for your help.

[rich454mc]

Well . I resoldered the q4 and checked it with a meter and it was ok. tried it in the car and it was fine for about 20 minutes and then it got stuck grounded again. I decided that I must have damaged the transistor by jumping the pins so I replaced it. I tried it again and its doing the exact same thing. once I plug in the ms2 it will be fine for 20 minutes and then pin 30 will ground itself even with no power to the ms2. what other items contribute to pin 30 output?

[rich454mc]

No one knows what components make up the fidle circuit?

[trakkies]

No one knows what components make up the fidle circuit?

If you do the test again of removing the daughter board, is the ground still present? if so, it must be a fault with the driver circuit above. Although I've not come across the symptoms you describe. Are either of the transistors getting very hot?

Still with the daughter card removed, if you jumper from +5v on the proto area to pin 34 on the processor socket, the relay should make. Is it a standard relay?

With MS unplugged, what it the resistance between pin 30 and pin 28? That should measure the relay coil.