DIY AIC
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Logistics Pro
Joined: Oct 2008
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From: Avilla, IN
DIY AIC
I will be doing a DIY AIC mod following these instructions: North Texas Power Stroke Association - DIY AIC Mod
I will be ammending these instructions so that I do not have to use the e-brake. Also I will be using a resistor in series with the potentiometer to change the RPM range available from the 1200-2500 to approximately 700-2000. By my calculations, I'll need 750 Ohms to achieve this.
The only thing I need to know is what the original voltage drop across the potentiometer is? I would assume it is 12V but I'm not sure.
I will be ammending these instructions so that I do not have to use the e-brake. Also I will be using a resistor in series with the potentiometer to change the RPM range available from the 1200-2500 to approximately 700-2000. By my calculations, I'll need 750 Ohms to achieve this.
The only thing I need to know is what the original voltage drop across the potentiometer is? I would assume it is 12V but I'm not sure.
Posting Guru
Joined: Dec 2008
Posts: 2,347
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From: Maysville, Kentucky
The problem is what is the amp draw on the circuit. Doesn't the TPS operate on a 5v system to tell the PCM what the throttle posistion is? So your AIC is telling the computer the voltage is higher then what it is. So you need to put 12 volts in and drop it to 5v at 0 ohms prior to the pot. which means more resistance less voltage and different throttle position so thinks the PCM.
Let me look in my electronic book tomorrow and I'll figure it out.
Let me look in my electronic book tomorrow and I'll figure it out.
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Logistics Pro
Joined: Oct 2008
Posts: 4,818
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From: Avilla, IN
Well, judging from the wiring diagram, it will already be dropped to 5V. So I guess that's my answer. I suppose I could put a resistor in there that will handle the power associated with a 12V circuit, and it will either be overkill or just right. Either way it will work.
Post Fiend
Joined: Dec 2010
Posts: 10,121
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From: Orrville, Ohio
My understanding of the design of this mod is that the 2k pot lowers the output voltage to a lower voltage to be read back to the PCM. That's what the pot is for. As you add resistance (measured in ohms) to a given voltage signal, that voltage drops. 2kohms won't affect it much but as you dial the pot closer to 0 ohms (more resistance and closer to a dead short) the output voltage of the signal will drop.
Post Fiend
Joined: Dec 2010
Posts: 10,121
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From: Orrville, Ohio
Thinking about doing this mod on my truck as well. It would be nice to aid in warm-ups on these cold Ohio mornings.
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Posting Guru
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From: Maysville, Kentucky
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Posting Guru
Joined: Nov 2007
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From: West Texas
I used teh exact same pot that guy said to use and it is a 0 to 3000 ohm. No idea why. You won't need a resistor though. And I also rigged it not to use the parking brake. Just ground the wire that goes to the parking brake switch instead. I really like mine and have been using it a lot.
Only weird thing is when I start it up cold I set it at 1000. After about 2-3 minutes it jumps up to about 1400. haven't figured that one out yet. Oh and to save some money, go to the junk yard and yank some relays from the underhood fuse box on a truck like ours. Just about any 5 pin ford relay will work the same.
Only weird thing is when I start it up cold I set it at 1000. After about 2-3 minutes it jumps up to about 1400. haven't figured that one out yet. Oh and to save some money, go to the junk yard and yank some relays from the underhood fuse box on a truck like ours. Just about any 5 pin ford relay will work the same.
Postmaster
Joined: Jun 2007
Posts: 2,795
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From: Rogue River, OR
Here is an alternative to all that work and time. These are almost plug n play. Make an offer and Free Shipping. 
Rog
7.3L DIESEL 95-98 7.3 FORD AUXILIARY IDLE CONTROL - eBay (item 270594395156 end time Jan-11-11 13:11:56 PST)
Rog
7.3L DIESEL 95-98 7.3 FORD AUXILIARY IDLE CONTROL - eBay (item 270594395156 end time Jan-11-11 13:11:56 PST)
Posting Guru
Joined: Nov 2007
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From: West Texas
Mine was free except for the pot. I robbed everything else off of other trucks. I mounted the **** in a open spot above the warning lights on the right side of the dash. I think it looks good. Right now the switch is mounted by my knee on the bottom of the dash. It's about to get moved to the console as soon as I get my new air seats and finish the center console. I'm putting all my gauges and switches in there.
Post Fiend
Joined: Dec 2010
Posts: 10,121
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From: Orrville, Ohio
RRranch, I have a theory on the idle speed increase after a few minutes. As the truck warms up the ECM adjusts the injector timing. Normally, the idle speed of the truck would be reset as well by the ECM but since this mod essentially fools the ECM into thinking that you are sitting in the seat with your foot on the throttle holding it at high idle, the idle speed is not controlled by the ECM. That's my theory at least....