Computerized System Monitor

[senrak]

Before I start pulling things apart, I wanted to ask for some advise here. Lord knows there are some smart guys on this site.
My 82 XJ is finally on the road after a frame up rebuild. I'm having trouble with the computerized monitor system. It intermittently stops working properly. There doesn't seem to be a reason, like going over a bump or vibration. It will start flashing the red light, then go through the check of the functions as it is suppose to, but for unknown reasons it will continue to do it over and over again. Sometimes it will not come on at startup as it should. Sometimes the tack goes off momentarily at the same time.
I'm thinking a bad ground, lose or broken wire. Maybe a bad connection in the unit itself. But, If anyone here has had this problem and knows what to look for, please chime in.
Thanks,
Dale

[mlew]

The monitor circuit boards are known to get loose solder joints and cause that exact problem . Take it apart and re-solder all the joints on the circuit board. Even the wires that attach . That should take care of it. The buttons on the display can also do the same thing. They are magnetic switches, just replace the little glass bulb in them. They are easy to find on the net, search for magnetic switch and you'll find them.

[senrak]

Circuit board looks good

Okay. Sounds logical.
Took apart the dash unit and got down to the monitor circuit board. Everything about the board looks great. It is even coated in liquid plastic to keep everything sealed including the wire connectors that plug into the board. I'm finding it hard to believe that there are any loose or corroded connections here. I'm on to double checking wires and magnetic switches.

Like I said, the tack goes dead at the same time. The tack has no connection to the monitor in the instrument panel, making me think the problem is an intermittent power loss at a connection elsewhere. .
Any ideas?

[senrak]

Magnitic Switches

I have taken the control switches apart and they seem to be working properly. How do you tell if the magnetic switches are bad? When I check them with an ohm meter they appear function as they should. Normally closed, when the magnet passes, they open momentarily.

[DiverRay]

I know the board LOOKS good, but re-flow the solder on all connections. You cannot see if it has a "cold solder joint" or if the connection has cracked with your eye. Sometimes it will test good with an ohm meter, but if you wiggle the wire or twist the board a little you MAY see it move. An analog meter works better at finding these things. Easy way to make sure it's NOT the problem is just re-solder the joints. Don't forget to add just a little solder to each joint, as that will help it flow properly.

[senrak]

Plastic on circuit board

The board has been coated in what must be a liquid plastic glue like substance.
How do I get that stuff off to actually get to the solder joints to re-flow them?

[crazy steve]

Before you start in on the monitor board, make sure all the other plug connections are good. 95% of all electrical problems on the XS/XJ bikes are bad connections, usually at the plugs.

[senrak]

Plastic Coating

Thanks for the advise Steve. I have read that in many threads before and followed it to the letter. I have been through every one of the connectors on this bike with a magnifying glass, various wire brushes, nail files, and dielectric grease. I believe this electrical problem is in that tiny 5%. That being said, I would like to be able to rule out a cold connection on this board, but I can't get past this plastic c>~p. I need to know how to get the coating on this circuit board off.
If anyone can answer that question please respond.

[CaptonZap]

Without resorting to harsh chemicals, you are stuck with mechanical removal. A pen knife, some good light, and a bit of time spent scraping should get the job done. Sometimes, if the coating is thick enough, and it's adhesion to the board is not that tenacious, you can get one edge of the blob lifted and peel a big chunk off.
On the other hand, adhering to the "better living through chemistry" mantra, you can try any paint remover that has as a main constituent methylene chloride. It is one of the harsh chemicals, so use care in handling it. Apply a small blob to the solder joint with a small brush, and remove when it softens the plastic coating, since it will also attack the circuit board. Most removers wash off with water, but be careful with the splash, since the movements are not designed to be exposed to moisture.

CZ

[senrak]

Thanks Capton.
I thought that may be the answer. I'll try peeling first, but this is so nicely sealed I'll do it with great reservation. What a PITA

[Jerry]

Make sure the carbon brushes in the XJ alternator (different system than on an XS) are not hanging up or giving you intermittent connection or output. The brushes are getting hard to find and Yamaha recommends a 10,000 mile maintenance schedule...a bit ridiculous given the brushes last a lot longer than that! The XJ went to the brush system to generate more power for the digital display.

16 years on this list and I've never heard of the XJ control board having cold solder joint problems. The rectifier board yes and I had to re-solder mine as other have had to do. That board is not coated, by the way.

Check your brushes and their carriers.

[senrak]

Thanks for the replies you guys!!
I am open to any and all. Like you said Jerry, that board looks great. I will look at the generator brushes. I'd hate to screw with the thing and have it not be the fix.