yvonnejim

The little light that tells you the "Best" time to shift sometimes works, sometimes doesn't. Where do I start?

rbcsaver

If like my 84 then is a small diode(LED), epoxied in the back, according to North Hollywood Speed and Clock, when they fixed mine. The signal comes directly from the motronics unit. My money would be on a bad diode or connection. I suspect you'll have to send it for repairs if you can't live without it. It is not neccessary for your cars function and some ppl have placed black tape over the "annoying light." Those tachs like the 84's are very expensive and tough to replace as new or used. Much cheaper to repair.
regards,
Steve

Lorenfb

"If like my 84 then is a small diode(LED), epoxied in the back," - rbcsaver -

Wrong!

"Those speedos like the 84's are very expensive and tough to replce as new or used. Much cheaper to repair." - rbcsaver -

The upshift indicator is in the tach & not in the speedo.

It's not a LED. It's a small incandescent bulb. A special chip in the tach monitors;
the injection pulse width (engine load), & the engine speed to determine when to upshift.

I wouldn't assume that the problem is in the tach. It could be a wiring problem from
the DME pin 11 which provides the engine load signal. Check the connections first.

KC911

IMO, if you're driving a 911 and your shift points are based upon the light, then you should have purchased a Prius . That 'best' time to shift light is for optimal fuel economy, and is worthless imo...drive the car like a sports car and ignore the light. Maybe someone else can explain the 'why', but when I first acquired my car (and was learning how to drive her), the light seemed to come on all the time and was extremely annoying. Now when I run through the gears more aggressively, the light rarely comes on (or maybe I've just learned to ignore it)... I'll disconnect mine (as have many others) when I have a need to access the tach.

Keith
'88 CE coupe

Peter Zimmermann

The light provided the Feds with shift points for new car emissions testing. It was never intended to be a suggestion as to how to actually drive the car. And yes, it's really irritating!
Pete

g-50cab

There's a shift light on my 87 carrera? Guess I have learned to ignore it!

KC911

Nah Jeremy, maybe you've never revved her high enough to coax the light on . Peter, thanks for the correction about the reason for the light (emmissions)...I mistakenly thought it was for gas mileage efficiency.

Keith

g-50cab

That's the only time I do recognize it - right before I hit the limiter!

yvonnejim

I just wanted everything to work in the car when it was new. Don't use the light, but thought it would be nice to have a completely original car.

DanS911

One of the local sages (Link) says it does have a purpose in performance driving. He says that when it comes on near the top ("right before I hit the limiter!") it's because you have topped out of the torque curve and might as well shift.
I wouldn't know 'cause mine is so intermittant it works about once a month!
But it is an interesting thought

Joshie

Sorry to hijack, but it made more sense then starting another thread.

What’s a safe rpm limit on these motors? My motor pull’s strong all the way to 6500rpm I’ve been past 7000rpm once or twice, and I felt in my opinion the car still had some pull left. Am I shifting far to late? Note; I don’t always drive it like I stole it, these are the times when I’m having a little squirt.

Mid 80's 3.0lt motor/weber conversion. Lead to believe may have minor head work and mild cams, if that helps.

Thanks.