Gauge Cluster connection question

[02Les]

Anyone know (for sure) what the spade-terminal on the back of the temp/fuel gauge, shown in the pics, is for? I thought about adding an earth lead, but then noticed it has an electrical "thingie" attached on the inside. It is on a '75 cluster, but not on a '73 cluster (just the 3 holes)

[BillWilliams]

No clue Les.

I have the older cars not the new 1975 model :-)

[im3crazy]

See attached drawing. Could it be the RT (red) and (BR) Brown connections to the clock?? (red cloud)

Notice that in your example that doesn't have the terminal that the circuit board is drilled for something. Maybe your earlier version didn't have a clock in the display??

The electrical device is a diode to prevent polarity reversal or backward voltage flow. It does not appear to show on the attachment, but maybe this is it at the red arrow??

[02Les]

See attached drawing. Could it be the RT (red) and (BR) Brown connections to the clock?? (red cloud)

Notice that in your example that doesn't have the terminal that the circuit board is drilled for something. Maybe your earlier version didn't have a clock in the display??

The electrical device is a diode to prevent polarity reversal or backward voltage flow. It does not appear to show on the attachment, but maybe this is it at the red arrow??

Looking at it closer - it's connected to the circuit board and appears to go to/from the BIG RED light for the brake level - handbrake. Curious.

I decided not to connect anything to it in case something went poof!

I looked at Keith Kreeger's "site" at the gauge rehab, and his gauge had this connection also.

I have several gauge clusters and the one with this connection is dated 3/75, some without it are 11/73 and 10/75, so it seems it is for a special purpose.

I love a mystery!

[BillWilliams]

I just wonder if that is for the "low fuel level" indicator.

But I thought that was an option for earlier models and some Euro models. That does not mean the connection could be there on the later cluster and why it is not there on the earlier models.

Yes, a mystery!

Do you have a way to put 12v to it and see what happens? We love a good poof? (as long as it is on your stuff Mr Les :-)

[im3crazy]

If it's connected to/from the brake light, possibly part of the later ignition interlock mess. I looked for a schem of the interlock, but didn't have it.

I like Bill's idea of a low fuel lamp if it's related to an indicator lamp on the display in question which the others don't have.

I would not suggest connecting 12vdc to it, however connecting 110vac may develop better smoke I love a mystery too. I guess we have to keep seeking the answer.

[Green2k2]

I think I remember a few guys talking about this a while back....not sure tho' so, don't get this tattooed on your forehead or anything...but

I "believe" it has something to do with the "e-brake on" indication..or "low brake fluid level" or something like that.

You may find it in a search.

[im3crazy]

I like where you're going with it. Maybe the diode prevents power backfeed from either the ebrake or the plunger switch on the brake fluid resevoir and allows either to light the brake warning lamp. I'll check the schems again, but I'm not seeing the detail on this.

Was there a warning lamp if one of the required safety devices were not engaged in automatics and later manuals?? e.g clutch in??

[Durandal]

well Ive got a cluster marked 10/73 (original to my car) and it has the terminal... further I have a brown with a white stripe wire that connects to it...

[02Les]

well Ive got a cluster marked 10/73 (original to my car) and it has the terminal... further I have a brown with a white stripe wire that connects to it...

Is your car an auto? That might narrow the search.

The earlier clusters have the provision (3 holes) for this terminal, so I can only think it's for some models and not required on others.

[ingraham]

It's shown on the double secret wiring diagram for a US '75 2002. A brown/grey wire from the handbrake lever switch attaches to it, and that illuminates the "Brake" warning light in the cluster.

The Brake warning light is also turned on via a brown/blue wire in the 12-conductor instrument cluster connector from the brake fluid level switch on the reservoir cap.

The brown/grey wire also goes to the seat belt interlock brain. The diode in the instrument cluster blocks the low fluid signal from the seat belt interlock.

You can safely ground this extra terminal, and that will turn on the Brake warning light.

If you apply 12 volts to this extra terminal when the handbrake is applied, you will fry the handbrake switch or your 12 volt source.

[02Les]

It's shown on the double secret wiring diagram for a US '75 2002. A brown/grey wire from the handbrake lever switch attaches to it, and that illuminates the "Brake" warning light in the cluster.

The Brake warning light is also turned on via a brown/blue wire in the 12-conductor instrument cluster connector from the brake fluid level switch on the reservoir cap.

The brown/grey wire also goes to the seat belt interlock brain. The diode in the instrument cluster blocks the low fluid signal from the seat belt interlock.

You can safely ground this extra terminal, and that will turn on the Brake warning light.

If you apply 12 volts to this extra terminal when the handbrake is applied, you will fry the handbrake switch or your 12 volt source.

Thanks Curt. I appreciate the info.

I have left well alone and put the cluster back as it was.

[Michael_V]

Interesting thread. Just ran into this same issue today when I switched out the cluster from my 1974 (that has this spade terminal and a brown/grey stripe wire from the multi connector bundle) for a 2/73 manufactured black 1973 cluster (that does not have this spade terminal). With my original wiring, the "Brake" light would illuminate when the emergency brake was on and also presumably for any actual failure. I noticed the brake light indicator for the mid-year cluster that I put in actually says "Brake Failure", so maybe it doesn't illuminate for the e-brake.

I just tied off the unused brown/grey stripe lead with electrical tape and put everthing else back in with the mid-year cluster. The e-brake does not illuminate the "Brake" light when set now, but the light does come on with the little tester button right above it.