Remove the 4O connection and connect a 1K resistor and a LED to 12V and pin 2 of the TIP122. This will test the TIP122.

If you don't have a spare 1k and LED, you can use the IAC LED on a JimStim which has a 1K and a LED. Connect one IAC LED pin (2nd pin from the bottom of the 10-pin header) to 12V and the other pin (bottom pin on the 10-pin header) to pin 2 of the TIP122. If you can get the LED to light up with the brightness somewhat proportional to the duty cycle then the TIP122 is correct and I would suspect the valve or the wiring.

Jean

 

I still suspect the TIP122 because the valve / the led can't do anything if there is just up to 0.5v attached to because that is what I get at the middle pin of the TIP122 andf therefore at OUT.

 

If your wiring is not correct, you won't get a correct voltage. Doing the LED test is quick and easy and you need to remove the 4O connection anyway to replace the TIP122.

So do the test just to make sure and then if it fails, replace the TIP122.

And by the way, once the 4O connection is off, check what voltage you get on it. You should have very close to 12V if everything is correct (with power on, of course).

Jean

 

Just did the LED test - the LED lights O.K. brighter to dimmer.

Also between pins 4O and 4M...

So the TIP is good then and something with my wiring or valve is wrong - it's OEM wiring, maybe the valve then.

 

It is still possible that the TIP122 has failed but will still work with the very small current of the LED. But at least, you're getting closer to a solution and you know that the PWM converter board is working as it should.

If you ground the 4O wire to the same ground as the one connected to pin 3 of the TIP122, does that activate the valve? If it does then change the TIP122. If it doesn't then check the wiring.

Jean

 

I tried it in the car again today and everything seems to be O.K. - I get voltages from near 0 to near 12V at the valve with the valve test and can hear the valve humming.

One error I made with wiing was wiring the A_GND to one of the GND pads at the connector board - which don't seem to be a real ground. But I had this changed with my last running car test...

Edit:
Last update - it works - thanks Jean and all.!

 

Glad to see it's working.

Jean

 

I put together one of these for a friend with a DIYPNP (yet to do mine) but when the IAC valve is connected the car will idle up to 5000rpm and hold. I unplugged the valve and it drops to the normal idle.

Is this likely to be a setting in tunerstudio or have I installed the TIP122 backwards?

TIP122 is mounted on the top of the board with the heatsink side facing out.

PWM is set to 30.5x1 and 16x on the PWM board.

The PWM board is assembled together with the TIP122 using the DIYPNP case as a heatsink.

 

Settings in TS wrong.

 

So that's the correct installation for the TIP122? I got the impression from elsewhere that it should be on the underside of the board with the heatsink side facing towards the edge of the board (other than the way I have it installed).

I have IN,OUT,5v,12v and GND connected, but I missed the A_GND. A_GND should be connected?

I fear I failed pretty badly. (Built in a hurry for someone else)

 

Yes, A_GND should be connected to a noise-free ground. The TIP122 should also be installed with a mica insulator and nylon screws/nuts.

 

Mica insulator between the heatsink and TIP122 or between the TIP122 and the PWM board?

I would have thought it wouldn't conduct heat properly with it between the heatsink.

 

Between the TIP122 and the heatsink. The mica insulator is a good conductor of heat but not a good one for electricity.

 

I also haven't completed this step (don't have the computer with me currently) What is standard in the R5 spot, and I presume this is 100% required?

I'll have to look into it when I'm in the same town as the car.

 

On the 50th read of the first post I think I'm starting to understand it a bit better.