Wow....well, I have to say I never knew that any of the DT250-B bikes had a light to indicate low injection oil.  Are you located in a country other than the U.S.?  Just wondering if some of these bikes that were sold elsewhere had that light, as everything that I've seen here shows that the amber light in the tach face is a turn signal indicator lamp.  Maybe in later model years like the 250-C or 250-D models?
 

DT250B does not and never had a low oil light from Yamaha.

For the 250/400 the first low oil light came on the monoshock 1977 "D" model.  Also got a neutral light at the same time.

Back to the issue...  the indicator light should connect to the green and dark brown turn signal wires.  Yes, the ones that both get power from the switch depending on if you switch right or left..

It's an ingenious system...  one wire gets power and the tiny bulb grounds through the turn signal filaments on the other side of the bike.  Not enough current can flow through the 3 watt bulb to make the other lights light up. 

Sometimes someone runs one side of the indicator bulb to ground thinking that's what it needs.    Not correct.  What indicator needs is one wire that powers with left turn on and the other wire with power when right turn on.  No ground wires.

Thanks for that explanation, MarkT.  Wow...that really is a rather unique setup!  Can I assume then that the connections I would be checking on would be located in the headlight shell (being the closest to where the indicator light and turn signal switch are located)?

Yes, if I remember correctly, the wires to the dash indicator connect right where the turn signal switch wires connect in the headlight bucket. 

Great!  Thanks MarkT.  I'll check all those connections out in the morning.  Thank you again for your help!

Well MarkT, you were spot on in terms of how I might find the turn signal instrument light wired.  Whoever tried to "fix" the lighting before I got the bike did just as you said; they wired one of the two wires to ground.  Once I corrected it to the way it was supposed to be wired, the turn signal indicator light lit up for both left and right.  Unfortunately, it lit up SOLID and like the turn signals themselves...it (and they) didn't flash at all.  So...I'm going to look at all 4 of the turn signal bulbs themselves to make sure I have the proper 1129 6V 17W bulbs and if so, I'll try pobit's flasher relay that I bought (again).  The challenge continues....

The pobit flasher should fix it.  It's common to have original flasher go bad like that. 

pobit unit is much less sensitive to needing exact bulb load too. 

I'll give it a shot MarkT.  Thanks.  Might be a while before I report back, as my tires arrived today so I'm planning on doing both tires, both sprockets and a new chain before I fire the bike up again.  I'll keep you posted!

After you've fitted the replacement flasher relay, you could have a bit of fun and try to fix the original one.

Gently prise out the fold overs at the wire end and, gently again, pull out the mechanism. It won't some out all the way, as one wire attaches it to the body.

At the top of the mechanism is a small set of points - gently open these up and clean the points faces.

Re-assemble, fit to bike (when convenient) and see if any improvement.

 

Well MarkT, I'm at a complete loss as to why I can't get my turn signals to flash.  After finally finishing up with installing new tires, sprockets and a chain, I finally got back to my electrical issue yesterday.  I had ordered all new and CORRECT bulbs for every socket on the bike and installed them all yesterday.  As noted previously, I also bought the new flasher relay sold by pobit on eBay.  With all the new bulbs installed, the turn signals still would not flash.  They all light up very brightly, but just do not flash.  So, I removed the stock flasher relay and put in the pobit unit.  Same thing...still no flashing of the turn signals.  I just don't get it.  Looking at the wiring diagram, there are only two wires (well, 3 if you include the black ground wire used with the OEM flasher relay) that go to the relay.  The solid brown wire looks like it ties into the main switch (with key), lighting switch (on left handlebar switch), both brake stop switches and the horn.  The brown/white wire appears to go directly to the flasher switch itself.  My question is this:  Is there any wire that if broken or not connected correctly, would allow the turn signals to light up solid but not flash?  I'm now wondering if the problem might lie in the left handlebar switch housing itself (I actually have a new switch but am trying to fix my issue without having to install it and route its harnesses & plugs, etc. to where they need to go), but I don't know if there is anything in that switch that if not making correct contact would allow the turn signals to light up but not flash.  Any help that anyone can offer is greatly appreciated.  Oh...the ONLY other thing that doesn't work now on the bike is the high beam indicator light on the tach.  The high beam itself works fine (in the sealed beam unit), but the blue indicator light does not.  While I'm not 100% sure, I don't see this being associated with the turn signal issue at all.