No Comunication with computer through serial

wvitpr · Post by **wvitpr** » Fri May 29, 2009 11:21 am

HI,

I have finally got my edis4 system going, motor starts and idles well. But the megajolt is not controlling the ignition advance? and I have lost comunication with through the serial cable? , it is very strange because before I installed into the car all was good, I set up a tables made ajustments etc..... operating perfectly. But now it is dead ???

Any ideas ??

I have checked voltages on the board all seem to be OK.

I think maybe I have blown it up

if by some chance I mixed up the saw and pip connections to the megajolt, would that fry it ??.

Regards

PR

Post by **brentp** » Fri May 29, 2009 5:30 pm

Hello,

What version MJLJ do you have? If a V4, does the power LED light up? Can you pull it out of the vehicle and test communications on the bench, powering it with a fresh 9V battery, and possibly with a different computer?

Was PIP and SAW switched by accident in your installation? It's unlikely that would cause any damage. Although, if there were any wiring errors it would be helpful to know for troubleshooting purposes.

Let us know what you find out.

wvitpr · Post by **wvitpr** » Fri May 29, 2009 11:48 pm

Hello,

What version MJLJ do you have? If a V4, does the power LED light up? Can you pull it out of the vehicle and test communications on the bench, powering it with a fresh 9V battery, and possibly with a different computer?

Was PIP and SAW switched by accident in your installation? It's unlikely that would cause any damage. Although, if there were any wiring errors it would be helpful to know for troubleshooting purposes.

Let us know what you find out.

Hi Brent,
Thankyou for your quick reply,

It is V4, the green led is very bright, I have already pulled it out of the car tested it on the bench with the same result.

I also tried it with a different computer, both of them have native serial ports.

For testing I hooked it up using the minimum wiring requirments only 4 connections power was connected correctly I know that !, and I I'm sure the pip and saw were correct.

When testing voltages on the bench with a 9V I did notice that the voltage across the battery terminals did drop to 7.6volts ? but I guess a 9V cannot supply much current.

I also tried testing with hyperterminal as per your instructions, with no result. After typing a 'C' I get nothing back from the MJ.

So I hope all of that will give you any clues ? ,

Regards

PR

Post by **brentp** » Sat May 30, 2009 7:22 am

Hello,

Your MJLJ was built as a kit correct? It's always a great idea to double check all of the solder joints- retouch any that seem marginal or suspicious.

With the voltage drop across the battery: while the unit is powered up, do any components get unusually hot?

wvitpr · Post by **wvitpr** » Sat May 30, 2009 10:30 am

HI,
Yes it was built from a kit,

After my last post I did some more voltage checks, but I think D3 might be the problem, it has the baterry voltage across it, compared to D2's 0.8 Volt, I also checked the output of U3, which I asume is a voltage regulator and it seems to be doing nothing 7.6IN and 6.3OUT. What would have caused this do you think ?,
as I am sure my power wiring was correct.

So I guess the obvious thing to do is replace the D2,D3 and the voltage reg, but what else do you think ?,

I have checked voltages on the board all seem to be OK.

I feel now when I first checked Votages it was the 9 volt bat that was bad

Thanks for help so far

PR