1967 Temperature Gauge

[Chris C.]

First mark on gauge reads 100 degrees.
What temperature is second mark?
Third mark on gauge reads 210 degrees.
What temperature is fourth mark?
Fifth mark on gauge reads 250 degrees.

My guess has always been the fourth mark is right in the middle of 210 - 250 (230 degrees), but the second mark is tougher to guess. Anyone know for sure?

Thanks Chris

[Larry M.]

Re: 1967 Temperature Gauge

Just answered this same question on the Corvette Forum a few days ago. According to Wilcox website, the first mark represents 109 ohms resistance. Based on original AC temperature sending units, 109 resistance represents a temperature of 180-190 F.

Any added resistance in the wiring from sender to dash or in the firewall connector block will l create a higher resistance at the dash gage and therefore show up as a lower temperature. Variations in original AC sending units with temperature can also affect the dash gage reading.

Best is to shoot the sending unit and intake manifold beneath it with a HIGH QUALITY and accurate IG gun when your gage just hits this mark. Then you know the right number for YOUR system.

Larry

[Ken A.]

Re: 1967 Temperature Gauge

That is incorrect, 180 temp =105 ohms. How do I know? I'm looking at the GM B/P as I type this. But you are correct in advising the OP to
figure out the right numbers for HIS system.

[Phillip M.]

Re: 1967 Temperature Gauge

Just so happens I removed the O.E.M. temp. sender from my '67 small block to fix a coolant leak, and decided to take some temperature readings just for curiosity. I placed a Styrofoam cup inside of a polypropylene container and filled both with water and microwaved to boiling (the PP container reduces heat loss in the inner foam cup of water). The sender was wired to the temp. gage in the car using the top connector of the car wiring and ground was wired onto the sender body. This was suspended in the cup of hot water along with an electronic meat probe with digital readout. This allowed an instantaneous readout of the car temp. gage and digital reference.
What I found is that the second hash mark on the car's gage corresponded to a 180 deg. F. reading on the reference probe. I then decided to do a resistance check comparison on the sender. I measured 120 ohms resistance at 180 deg. F., and 586 ohms resistance at 72 deg. F.
Of course these readings may be particular to my car only, but it satisfied my curiosity in the reading of the temp. gage in my car.

[Timothy B.]

Re: 1967 Temperature Gauge

Phillip,

When I checked my 63 sender resistance it was approx. 110-115 ohm's at 180* running engine temperature.

[Gerard F.]

Re: 1967 Temperature Gauge

Chris,

I think Larry is correct, the second mark on a 67 temperature gage is somewhere between 180-190d.

If you want to check it on the road by just lifting the hood, try one of these:



Yes it is just a cooking thermometer taped to the radiator hose. They call it an analog temperature gage ( I could not explain it to my wife when I stole it from the kitchen drawer)

The variance in the resistance of the sender and the gage in these older cars is not precise. But if you are consistently hitting the 210 mark and above you have a problem.

I had that problem with my 67 327 with its original aluminum radiator. The problem was resolved with a flush of the radiator, a reverse flush of the engine, new refurbed (correct dated) water pump and a new fan clutch. Now I only slightly get past the second mark, cruising in the desert or traffic in hot summer weather (and with the Vintage Air blasting). If it hits 210 I turn the AC off.

[Ernie F.]

Re: 1967 Temperature Gauge

The chart posted below was taken from multiple original NOS gauges and even used original working gauges and has been our calibration chart for years. The scale is so non-linear that even 20 ohms on the colder side won't make much of a difference and the difference between 105 and 109 ohms input in regards to the first has mark would be minimal. Either way, these are the gauge expected (averaged) inputs required from the sender. As we all probably know, if you find an aftermarket sender that puts out like the original senders you've found your needle in a haystack, it's always best to try to find an original.

Due to the issues created by the crappy senders today, I make an adjustable resistor for the back of the gauge which will allow you to make a linear change in the non-linear gauge for all temperature gauges 1965-1982. Simply put, you can adjust the gauge to pretty much match the sender with accuracy. It's on our website and it works! I'm not sure if me posting this here violates some NCRS posting rules because it has our logo on it, but if it does I'm sorry and will remove it if needed.