Re: upshift indicator [4k/CGT]

[ejfluhr@austin.ibm.com (Fluhr)]

>Does your upshift indicator light come on?  Mine never has.  I haven't 
>thought much about it, until last night my friend told me he replaced his 
>vacuum advance on his distributor because it was bad and his light started 
>working (made his car faster of course too).

Yes, a broken vacuum advance diaphram in the distributor can prevent the
upshift light from turning on.  There is also a small switch located on
the vacuum line to the distributor (usually very close to the distributor)
with two electrical wires and input and output vacuum ports.  This
measures the level of vacuum and sends a signal to the upshift control
unit, telling it to turn off (or stay off) if the engine is under
heavy load (i.e. relatively little vacuum).  Check that this switch is
in place and attached to the two-wire electrical connector.

>I guess the simplest way to check for a failed vacuum advance would be to 
>check the timing with it disconnected and compare that with the timing 
>with it connected (while accelerating both times).

Just put a vacuum hose on the vacuum advance in the distributor and
suck on the hose.  If it is working, you should feel it.  (Ummm....
NO sexual innuendos here, please!! :)

Another way to check the system is to pull the vacuum hose off of the
distributor and close it off.  This will emulate a working vacuum
advance (at least, to the upshift unit), and you can see if the upshift
light comes on when running the engine.

>Is there a better way to fix the upshift light (another cause beside a
>failed vacuum advance)?  I doubt it's the bulb, ya think?

Another important part to check is the upshift control unit.  This is
located in the fuse box under the hood...I think in relay position #4.
Mine had two or three bad solder joints at the base where the relay
pins connect to the internal epoxy board.  I resoldered the relay and
it has worked fine since then. 

The control unit receives a signal from the coil to determine engine
RPM.  You should check that is wire is not broken, and that the contacts
at the coil and fuse box are clean.

In your case, with an '85-'87 CGT, I seriously doubt it is the upshift
control light, because it is a small LED and is unlikely to burn out.  On
the '81-'84 Coupe, however, the upshift indicator is an Osram bulb
(like the other warning light bulbs in the dash) and can blow itself out.

Later,
Eric
'85 Coupe GT
---
Eric J. Fluhr                                Email:  ejfluhr@austin.ibm.com
630FP Logic/Circuit Design                   Phone:  (512) 838-7589
IBM Server Group                             Austin, TX