Board voltage low
Moderators: jsmcortina, muythaibxr
Board voltage low
Let me preface by saying that I know just enough about electronics to be dangerous.
The backstory:
I build an MS2 v3.0, loaded firmware and bench tested for approximately 30 mins on a JimStim with perfect results. The ECU then sat on the bench for about 6 weeks while I built the engine and wired the harness. I installed the ECU and powered it up, not realizing I had not attached the chassis ground. It is possible that it made intermittent contact with the ground stud while I was puzzling things out. I attached the ground and attempted to do a sensor check. I could not get the PC to find the MS so I spent 4 hours chasing a com problem with no results. I then removed the ECU and attempted to test it with the Stim and found it would power up and work normally for 15-30 seconds before powering down. I volt tested the board and found I did not have 12v anywhere I was supposed to, more like 2.5v. I resoldered all of the ground and power pins at the 37 pin connector with the same results.
How should I proceed?
The backstory:
I build an MS2 v3.0, loaded firmware and bench tested for approximately 30 mins on a JimStim with perfect results. The ECU then sat on the bench for about 6 weeks while I built the engine and wired the harness. I installed the ECU and powered it up, not realizing I had not attached the chassis ground. It is possible that it made intermittent contact with the ground stud while I was puzzling things out. I attached the ground and attempted to do a sensor check. I could not get the PC to find the MS so I spent 4 hours chasing a com problem with no results. I then removed the ECU and attempted to test it with the Stim and found it would power up and work normally for 15-30 seconds before powering down. I volt tested the board and found I did not have 12v anywhere I was supposed to, more like 2.5v. I resoldered all of the ground and power pins at the 37 pin connector with the same results.
How should I proceed?
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- Super MS/Extra'er
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- Location: Walnut Creek, Calif. USA
Re: Board voltage low
Remove the daughterboard (MS2) and check for voltages on the 40-pin socket of the mainboard, per the manual "build instructions". Post results.
Re: Board voltage low
Found the problem. Too much thermal paste on Q9. I cleaned off the excess, reassembled and bench tested for over an hour. Flawless!
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- Super MS/Extra'er
- Posts: 6828
- Joined: Sun May 15, 2011 11:41 am
- Location: Walnut Creek, Calif. USA
Re: Board voltage low
I'm glad you got it going, of course, but "too much thermal paste" can't possibly have caused the problem. You must have disturbed something that was shorting when cleaning Q9.
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- Super MS/Extra'er
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Re: Board voltage low
Actually, some thermal pastes are conductive (for example those containing silver). They should be avoided in any application where you need isolation. Using little paste may help to keep isolation but that would still not be a recommended method as this may change with time and could lead to a less than optimal thermal performance.billr wrote:I'm glad you got it going, of course, but "too much thermal paste" can't possibly have caused the problem. You must have disturbed something that was shorting when cleaning Q9.
Jean
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- Super MS/Extra'er
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- Joined: Sun May 15, 2011 11:41 am
- Location: Walnut Creek, Calif. USA
Re: Board voltage low
Ah, I wasn't considering electrically conductive thermal compounds!
Re: Board voltage low
The heat sink paste that comes with DIYAutotune MS kits is in fact conductive. I have switched to using a non-conductive silicone based heat sink paste for any TO-220 cased component that needs a mica insulator.billr wrote:Ah, I wasn't considering electrically conductive thermal compounds!
Last edited by prof315 on Sun May 21, 2017 3:55 am, edited 1 time in total.
Linfert Performance/321 Motorsports
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!
Re: Board voltage low
But surely, if only for looks, you'd clean off any excess afterwards? In the same way as you'd clean off flux residue?
Rover SD1 3.5 EFI
MS2 V3
EDIS
Tech Edge O2
London UK.
MS2 V3
EDIS
Tech Edge O2
London UK.
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- Super MS/Extra'er
- Posts: 9130
- Joined: Sun May 02, 2004 6:51 am
- Location: Quebec, Canada
- Contact:
Re: Board voltage low
Of course, you can clean off the excess but even that might not be enough if the paste is conductive. And it's not the same thing as flux residue because a bit more thermal paste is better than not enough.DaveEFI wrote:But surely, if only for looks, you'd clean off any excess afterwards? In the same way as you'd clean off flux residue?
Jean
Re: Board voltage low
Surely if the problem was the supplied paste in the kits, others would have had the same result?
The reason I clean off any excess paste is it remains sticky. So might pick up something from the workbench that could cause a short.
The reason I clean off any excess paste is it remains sticky. So might pick up something from the workbench that could cause a short.
Rover SD1 3.5 EFI
MS2 V3
EDIS
Tech Edge O2
London UK.
MS2 V3
EDIS
Tech Edge O2
London UK.
Re: Board voltage low
Others have.DaveEFI wrote:Surely if the problem was the supplied paste in the kits, others would have had the same result?
The reason I clean off any excess paste is it remains sticky. So might pick up something from the workbench that could cause a short.
Linfert Performance/321 Motorsports
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!
Re: Board voltage low
My enthusiasm is short lived. Another related problem has reared its ugly head. The ECU runs forever on the Stim, all voltages check good. When I plug it into the car harness it will run for 2-minutes and shut down. The 12v side is good, but 5v side drops slowly to 2 volts.
Any ideas?
Any ideas?
Re: Board voltage low
I just logged the episode and it shows the battery voltage (reportedly) starts to rise exponentially from start up peaking at about 25V and then shut down occurs.
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- Super MS/Extra'er
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- Joined: Sun May 15, 2011 11:41 am
- Location: Walnut Creek, Calif. USA
Re: Board voltage low
Disconnect the MAP sensor and TPS and anything else connected to the 5V ref; disconnect right at the MS DB37 connector. See if that changes things.
Re: Board voltage low
Ok, I've narrowed it down to the distributor pickup. I must have it wired incorrectly. Anyone familiar with Bosch Hall effect? 3 wires, red, green, black.
Re: Board voltage low
Yes the connector on the distributor side typically has a + a - and a 0 + is 12V - is ground and 0 is signal. The signal pin is pretty much always the center pineman911 wrote:Ok, I've narrowed it down to the distributor pickup. I must have it wired incorrectly. Anyone familiar with Bosch Hall effect? 3 wires, red, green, black.
Linfert Performance/321 Motorsports
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!
SCCA 2019 SM National Champion Crew Chief
SCCA 2023 FP National Champion Tuner/electrical engineer
100s of MS systems built installed and tuned
Support the developers!