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Help with building your Speeduino, installing it, getting it to run etc.
By gbilski
#40956
I just have a question on wiring the U4AC for a PWM 2 wire IAC. There is an idel1 and an idle2 pin, should I be using idle1 for one wire of the IAC and and the other IAC wire to ground?
Thanks,
Gary
By pazi88
#40957
Nope. 2wire PWM iac needs to be wired to switched +12v and idle1. Speeduino only grounds the idle outputs.
By pazi88
#40962
Correct. Also remember to have the 12v switched. Not constantly powered on. Preferably same 12v source as speeduino itself.
By gbilski
#40963
Thank you very much for your replies. I keep forgetting that Speeduino mostly switches grounds. That is the last bit I needed to know, so now I can finish wiring up the car. I am building a complete new engine harness as the existing one is 29 years old and I also want to be able to go back to standard as this car is also pretty rare here.
Last edited by gbilski on Sat Feb 15, 2020 6:15 pm, edited 1 time in total.
By gbilski
#40964
@GhjEng, that is a really helpful diagram. I have found the lack of U4AC specific information has taken me quite some time to figure out how the connections work.
By GhjEng
#40967
gbilski wrote:
Sat Feb 15, 2020 6:08 pm
@GhjEng, that is a really helpful diagram. I have found the lack of U4AC specific information has taken me quite some time to figure out how the connections work.
No problem, happy to help. I’ve got the UA4C too... best thing I can suggest is to go to the UA4C Github and grab the board schematics. It shows everything you need to figure out what’s going on.
By gbilski
#40968
Yes, I do have them, but I only have very basic understanding of reading schematics. Even now that I know that it is switching to earth, I still don't understand the idle1 circuit. I have been working on cars for nearly 40 years, but never really did much with electronics like this.
By gbilski
#41060
No, I don't quite get the schematic, I understand that the circuit grounds the IAC with a PWM signal. I will think on it a little more.

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