[Tigers] Instrument Sttabilizer frolics

[Stu Brennan]

Now I'm just guessing, but I suspect the other two parts are a resistor and 
a zener in the 10 to 11 volt range.   The zener provides the steady voltage 
that the transistor sort of tracks, so that its emitter is always at about 
10V as long as the battery voltage is above about 11.   The resistor feeds 
some current from the Battery voltage  to the zener, to keep its voltage up. 
The problem with this design is that it's not short proof, and it will keep 
trying to pump  current into the 10V line until the transistor melts.

Stu

-----Original Message----- 
From: Rollright at aol.com
Sent: Thursday, August 23, 2012 3:37 PM
To: tigers at Autox.Team.Net
Cc: todbrown at roadrunner.com
Subject: [Tigers] Instrument Sttabilizer frolics

Hello,

Well after looking under the dash in the usual place (and unusual ones as
well), my trusty local garage found the verdamnt  "I.S." where it was
supposed to be, but covered and obscured by a dealer-installed hazard 
warning
flasher. I forgot to look under it.....duh.  BTW, the Steve Laifman  seat
removal pins have worked great.
    Troubleshooting: my IS-governed gauges gave  strange readings. The temp
seemed to run high (on a hot day over 250  indicated even with Derale fan
and fan shroud bottom extension from Canada).  Fuel gauge was funky, reading
OK on the right or full end of the  gauge, but when it hit about 2/5 full,
it dropped to zero. My .IS,  under  test yielded 5 Volts and was of the 
newer
semi-conductor type. Got a new one  from SS and it measured 10 Volts
installed.
    With new IS installed I tested the temp gauge this  weekend in full
engine-running heat-soak. What had been 250 + was reading 195.  With the
electric fan running it goes even lower. Gas hasn't gone down far  enough to
report as of yet.
    Make note: if your fuel and especially temp gauge  read where they
shouldn't, check the Instrument Stabilizer voltage!
    BTW: I took the old IS apart and there are only 3  electronic
components inside: an NPN transistor labeled FZT651 and two ancillary 
surface mount
components that look like either capacitors or resistors...that's  it.
One of the ancillary components is dead (hence the half voltage).

Hope this is of help to someone.......

Best regards,
Jim Armstrong
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