Wrong Battery Voltage
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Wrong Battery Voltage
I installed the MS2 daughter board and now have an issue with the battery voltage. The indicated voltage is exactly 1/2 the actual voltage. I installed the jumper to power the 4-wire IAC. Any ideas on what this is or how to trouble shoot it?
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: Wrong Battery Voltage
Start by measuring the voltage across the two Boot terminals on the main board (NOT on the daughter board). They're a voltage divider that feeds a signal that should be 1/6 the battery voltage in to the Megasquirt. What voltage do you see there?
Re: Wrong Battery Voltage
The two resistors are good. The voltage at pin 1 on the CPU socket is 5V. The voltage at S12C is 10.4V. The voltage at pins 1 and 3 on U5 is 5V and 6.66V. The voltage at the boot pins on the main board is 1.2V. The batter is exaclty 12V. So, something is wrong.
Re: Wrong Battery Voltage
Pin 1 on U5 measures 10.4V with the MS2 board out and 6.66V with the MS2 in. The voltage at the boot pins on the board is 1.8V with the MS2 board out.
Re: Wrong Battery Voltage
I considered the MS2 board may be bad so I pulled the 12V jumper and installed the MS1 CPU. Same problem. Pin 1on U5 shows 10.4V CPU out and 9V CPU in. The battery voltage now reads 9V instead of 6V. This is definite something on the board. Any help would be much appreciated.
Re: Wrong Battery Voltage
I found the problem. The power supply for the MS was fubar. As soon as the MS powered up the voltage would drop off. I guess the MS2 draws more power so the power drop off was steeper. I bypassed directly to the cars battery and all is good.