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Charter Member
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Discussion Starter #1
Autometer vintage showing around 12v, sometimes just below and sometimes up to maybe 13v. Never up to 14/14,5.

Measure at battery and is always around 13.6/13,8 depending on fan etc.

I have an ongoing dilemma with some component in my harness that is very sensitive to lower voltage and have problem fire the engine up when its hot. I think there is a relay or maybe something with the ignition that fails when the enginebay is really hot and the car has set for 5-10 mins in summer. I´ve had this since day one and I´ve decided to fix it now or I´ll go mad. It can also be a diagnostics-problem which I´ll try to explain:

The Autometer is hooked up to the original harness from a, around -90, Mustang. My question to an EEC-nerd or expert if you will is: Where does the EECIV get its "voltage reference" from to calculate ignition/fuel/spark when start with hot engine? Maybe its from the same pin my Autometer is hooked up to and therefor bugging me (for 5 long years now). I´ve been tweaking with my Tweecer some time now and is well familiar with the graphs and tables in the EEC but this I don´t know. Is the EECIV getting reference from just the powersupply itself? I read something about a "charge indicator", a red/green cable out of the main harness under the dash.

Help on this is ongoing nightmare (I´ve posted at least 3-4 topics on this thru the years) is of course appriciated...
 

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Mark 3.1 (Sold)
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894 Posts
I am running the Autometer ultra-lite gages, and noticed an issue with the volt meter. It has an extra terminal on the back that is not used. If you put ignition voltage on this (S?) terminal, instead of the I terminal, the voltage will read low.
DD
 

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Premium Member
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17,956 Posts
Autometer vintage showing around 12v, sometimes just below and sometimes up to maybe 13v. Never up to 14/14,5.

Measure at battery and is always around 13.6/13,8 depending on fan etc.
The real question is, why is this happening?
 

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Mark 3.1 (Sold)
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Let me explain again - with my Autometer volt meter, hook 14 volts from the ignition circuit to the incorrect (S) terminal on the gauge and the gauge reads 12 volts. Hook 14 volts from the ignition circuit to the I terminal and it reads 14 volts. In all cases the system voltage is 14 volts, but connected to the incorrect terminal on the gauge and you get an erroneous reading.
DD
 

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Premium Member
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DD, that makes perfect sense. I'v seen that before.

But that's not what the OP said. Measuring at the battery should be 14.0-14.5V. Although he may have the gauge wired to the wrong post, he also has a problem with system voltage. The question is, Why?
 

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Mark 3.1 (Sold)
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He states that his system voltage is between 13.6 to 13.8 volts which is at the low end of normal. While I'd like to see it closer to 14.0, I think it is considered normal. His observed voltage at the gauge is not normal, but is a display error not a bus voltage issue.
DD
 

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Junior Charter Member
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He mention he was getting that reading at battery with fan on, etc. That voltage maybe normal then. If nothing on it should be between 13.8 and 14.6 normally.
 
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