Another strange Cluster Question

...this time about the TBI 9C1 cluster.

The 94-96 cluster can be switched from mph to km/h, standard feature, never seen a car without it.

But - trust me on this - the digital Speed Display of the 1991-1993 9C1 Caprices can do this, too. I just don't know how.

I know it can be switched for a fact, a) because "km/h" lights up on the display's top right hand corner during self test, and b) because I actually owned a 1991 9C1 many years ago that had this feature activated. The car came from the US Air Force in Italy, and it seems they did this to all their cars. Sadly enough, I was too young and careless to take note of HOW they did it, all I remember is it was done by means of a simple On/Off Switch spliced into the existing harness.

I've spent countless hours searching the web and staring at wiring diagrams, but I just don't get it. It IS there, probably put there by GM for the Export LTZ cars, but just HOW do I get it to work?

I've even studied the Export Wiring Diagrams that don't come in the FSM, but again, I can't find it.

It is probably one simple wire that will do the trick. Any ideas, anybody?

Would it have anything to do with the VSS? different pulse would tell the gauge what to read in? Just a guess.... Anyone have gauge I can inspect????

Ironfistdog wrote:

Would it have anything to do with the VSS? different pulse would tell the gauge what to read in? Just a guess.... Anyone have gauge I can inspect????

Theres the one in my cah that still needs the tach wired

WTF! stop day dreaming about go-karts and ice cream and get on that!!!!!
Lol seriously next time your out here I can hook it up if you want. I'm still not in the house..... I'm getting pissed!

Ironfistdog wrote:

Would it have anything to do with the VSS? different pulse would tell the gauge what to read in? Just a guess.... Anyone have gauge I can inspect????

Dunno... On the 94-96, is all seems to happen in the display unit itself. If you had a gauge to inspect, what would you be looking for?

I would get a spare set of harnesses for the back and see what pins were missing.
I would then try to run power to the pink/black wires and ground the black and black/white wires on a good loose battery.
Then get a spare wire with the correct pin and break off the lock tab, if probably probe each empty slot to see what they went too,
You can figure out which wire goes to the speedo with a ship manual or online. And I believe you can check that wire by touching to the power ( it may already be lit because of the pink/Black wires). Thats where I'd start. You could also see if you can compare what the VSS pluse in an export is to the regular American VSS.

Ironfistdog wrote:

Would it have anything to do with the VSS? different pulse would tell the gauge what to read in? Just a guess.... Anyone have gauge I can inspect????

No, VSS will be constant, just the processing inside the cluster will change.

SPCS wrote:

Dunno... On the 94-96, is all seems to happen in the display unit itself. If you had a gauge to inspect, what would you be looking for?

On the '94-'96 cars, eng/metric is selected by grounding a specific cluster pin. The switch is external to the cluster, but the changes are limited to the cluster display.

The '91 parts manual shows 5 specific clusters:

1. Domestic
2. Domestic SEO (9C1)
3. Export
4. Canada
5. Export SEO (9C1)

No illustrations of the differences, and no english/metric switch is listed, implying that if it was there, then the switch was part of the cluster itself.

Either ENG/MET select was specific to the export SEO cluster, and the only way to add the feature is to procure that one, or it was in all the SEO clusters, but switch wasn't installed to enable it (very possible).

So, using a '91-'93 SEO or LTZ cluster, open it up & inspect the circuit board to see if there were provisions for a switch, and try jumping those connections, or grounding any unused pins on the display.

- J

My 9C1 cluster flashes MPH/KPH on startup. My guess is that the functionality is built into the cluster. I can't imagine GM building an export 9C1 cluster when there were so few domestic ones on the whole.

That said, I have one of my spares semi taken apart. If I get a chance today, I'll take the circuit board out and post some pics.

Ironfistdog wrote:

I would get a spare set of harnesses for the back and see what pins were missing.
I would then try to run power to the pink/black wires and ground the black and black/white wires on a good loose battery.
Then get a spare wire with the correct pin and break off the lock tab, if probably probe each empty slot to see what they went too,
You can figure out which wire goes to the speedo with a ship manual or online. And I believe you can check that wire by touching to the power ( it may already be lit because of the pink/Black wires). Thats where I'd start. You could also see if you can compare what the VSS pluse in an export is to the regular American VSS.

Uh oh. This is Germany. No spare sets of anything for a B-Body. But it sounds simple enough. On the other hand,

JaySS wrote:

On the '94-'96 cars, eng/metric is selected by grounding a specific cluster pin.

this is exactly what I gathered from the 94-96, and if the 91-93 cluster works the same, I wouldn't be able to find it that way? I'd have to temporarily GROUND a specific terminal in order to set off the switch... Ok, now that could be done the same way, I get the idea... Is it safe to just go and apply 12 volts to any terminal? No risk of shorting something out?

JaySS wrote:

Either ENG/MET select was specific to the export SEO cluster, and the only way to add the feature is to procure that one, or it was in all the SEO clusters, but switch wasn't installed to enable it (very possible).

So, using a '91-'93 SEO or LTZ cluster, open it up & inspect the circuit board to see if there were provisions for a switch, and try jumping those connections, or grounding any unused pins on the display.

The car I had back then was not an Export model. The primary switch was definitely installed locally, not from the factory, it was just a cheap on/off switch in a drilled hole in the dash, spliced into the wiring harness. Not the type of pulse switch as in the 94-96s, either, but a rocker switch with one OFF and one ON position. I guess I'll be looking for unused terminals, then...

Cadet57 wrote:

My 9C1 cluster flashes MPH/KPH on startup. My guess is that the functionality is built into the cluster. I can't imagine GM building an export 9C1 cluster when there were so few domestic ones on the whole.

That said, I have one of my spares semi taken apart. If I get a chance today, I'll take the circuit board out and post some pics.

Please, please do so! As I said, no spares for TBI car clusters in this country, if I accidentially damage what I have, then I'm essentially clusterless.

Ahh, crap. There's like a million unused terminals on those connectors.