'67 Gauge Cluster problems...

[Patrick T.]

I'm at the end of my rope on these two items....the parking brake alarm light and the temperature gauge.

The original temp gauge and the rest of the cluster was rebuilt by a well known vendor, I reinstalled it with a new sending unit and it worked fine for months while I was running the car in the driveway.

Now I'm driving the car on the road and when the engine heats up after about 10 miles, the temp needle pegs all the way to the right. When the engine cools down in the garage after a while, the needle goes back to the left and everything is OK again.

Same thing happens with the parking alarm light. I put a new switch at the parking brake console. As soon as the car heats up, the parking warning light comes on and won't go off until the car cools down.

It seems to me that the cause these problems may be at the same source but I haven't got a clue at this point of what it might be. I also have a new NOS signal switch in the steering column. All the other gauges work Ok. Maybe someone could point me in the right direction. Thanks for any advice. PT

[John H.]

Re: '67 Gauge Cluster problems...

Same thing happens with the parking alarm light. I put a new switch at the parking brake console. As soon as the car heats up, the parking warning light comes on and won't go off until the car cools down. PT

Pat -

That "Brake" warning light can be activated by two sources - the switch on the parking brake handle, and the differential pressure switch in the distribution block below the master cylinder (tan wire). Disconnect each one separately and see under which condition the light comes on.

[Patrick T.]

Re: '67 Gauge Cluster problems...

Pat -

That "Brake" warning light can be activated by two sources - the switch on the parking brake handle, and the differential pressure switch in the distribution block below the master cylinder (tan wire). Disconnect each one separately and see under which condition the light comes on.

Thanks John, I try disconnecting the M/C proportioning valve wire first, maybe the valve is bad? PT

[John H.]

Re: '67 Gauge Cluster problems...

Thanks John, I try disconnecting the M/C proportioning valve wire first, maybe the valve is bad? PT

Pat -

If you disconnect the wire from the differential pressure switch and the warning light still comes on, the issue is with the parking brake switch or wiring (when you pull up the handle, the switch closes, grounding the circuit, which illuminates the lamp).

[Patrick T.]

Re: '67 Gauge Cluster problems...

Pat -

If you disconnect the wire from the differential pressure switch and the warning light still comes on, the issue is with the parking brake switch or wiring (when you pull up the handle, the switch closes, grounding the circuit, which illuminates the lamp).

Thanks John, I did just that and will take it out for a run tomorrow. PT

[Jack H.]

Re: '67 Gauge Cluster problems...

Your temp gauge 'pegging' problem may be related to ground reference in the cluster. The temp gauge needle position is dictated by two opposing electro magnets (one pulls the needle to the cold side, the other to the hot side of the dial). That keeps the needle from 'bouncing' in response to road shock/vibration.

The 'cold side' electro-magnet is fixed in magnetic field intensity while the 'hot side' varies in field intensity based on current flow through the temp sender. If the cold side electro magnet 'loses' its ground reference (e.g. gauge isn't FIRMLY seated in the instrument cluster with good/solid electrical contact), it stops applying magnetics and the hot side of the gauge dominates causing the pointer needle to 'peg' hot...

[Patrick T.]

Re: '67 Gauge Cluster problems...

Thanks for the advice Jack, I'll just go ahead and check the ground terminals to make sure they are clean and tight. PT

[Gerard F.]

Re: '67 Gauge Cluster problems...

Thanks for the advice Jack, I'll just go ahead and check the ground terminals to make sure they are clean and tight. PT

PT

You know, if you ground the temperature sender wire connector at the sender end, the temperature gauge will peg all the way to the right.

If you ground the low brake warning switch wire connector below the master cylinder, the brake warning light goes on.

Funny, that my 67 wiring diagram shows these two connections side by side in the firewall harness connector. Maybe the problem has something to do with the firewall harness connector when the engine gets hot. Maybe one gets grounded and grounds the other at the firewall connector.

Just a thought.

[Jack H.]

Re: '67 Gauge Cluster problems...

An EXCELLENT suggestion, Jerry!