SECA Computer Problem?

I have a 81 750 SECA. The tail light warning is on all the time while the tail light works fine. I checked the voltage and ground, both are fine and the Bulbs are good. Occasionally the "TAIL" light warning will go off, but comes back on after a short time while riding?

Anyone else have this issue or know what could be causing this?

Thanks

Lyle

 

a dirty bulb socket could cause this... also, a mismatched bulb would, too.

make sure the bulb is an 1157 or equivalent (not an LED replacement).. make sure it's not forced into the socket backwards, and it probably wouldn't hurt to clean the contacts inside the bulb socket with some emery paper.

 

The bulbs are new, Yamaha spec bulbs. They are inserted in the correct orientation, and the contacts are clean. I even have 2 other sets of sockets, and the wanring light still comes on? I'm beginning to wonder if the computer it self is faulty?

 

The tail light check is based on measuring current draw for the tail light at all times, and for a higher current draw when the brake light is actuated. The computer also pulses the brake light at startup (too quick to see) to check that the filaments are good.

Current draw is sensed by running supply to the tail lights through a couple of power resistors in the computer. If the resistors were bad, then the tail light, or brake light, wouldn't light, so that shouldn't be part of the problem. It could be that the comparator input to the CPU is bad, I suppose.

Have you noticed any pattern to when the warning comes on? Like, maybe, it comes on the first time you've held the brake for more than a split second? Have you verified that the brake light is lighting properly, and on both bulbs?

Cheers,
Paul

 

First of all. Thanks everyone for the help.

When the bike is started, it goes through the system diagnostic check, the TAIL indicator comes on, the the red warning light soon after?

There is no patter on when it goes off. Is there a way to test the comparitor on the bike with out stripping the gauge cluster?

I have thought about tearing down the gauge cluster and reflowing the solder joints just is case a solder joint on the circuit card assemby is either cracked or corroded?

Any thoughts?

 

Not really. I mean, you could check resistance between the input and output pin of the harness for the tail light and brake light (which you would have to trace out manually), but anything more would require opening the cluster and removing the computer.

The resistors are .47 Ohms for the tail light and .12 Ohms for the brake light. Some pictures here: http://www.xjbikes.com/Forums/viewtopic/t=14068.html

I'll ask again, though: did you verify that the brake light is coming on correctly and on both bulbs, when the brake is pressed/pulled?

Thanks,
Paul

 

Both bulbs are working when either brake is applied. I will measure the resistance this evening and let you know what I find. Thanks again.

 

Both bulbs are working when either brake is applied. I will measure the resistance this evening and let you know what I find. Thanks again.

Also, you claim you converted your XJ to fuel injection? Can you post a thread on how that was accomplished?

 

One good thing, I think, is that with the number of 750 SECA owners on this site that ripped off the stock cluster and switched to something else, there should be a few good used computers available.

Your idea about cold solder or a cracked trace might be correct, though.

P.S. The input and output wires you'd need to measure to check the resitors are accessible in the headlight bucket.

Cheers,
Paul

 

Sorry it took so long to post this update:

I found the problem. There was a module hooked up in-line with the the wire feeding 12vdc to the break lights. The module is supposed to make the break lights blink slightly when voltage is applied. Apparently this module was cuttinh the voltage too much tripping the sensor on the computer. I removed the module. Now the computer is working fine.

Thanks