1963 Corvette Temperature Gauge

[Timothy B.]

I am trying to determine if the needle on my temperature gauge is installed incorrectly. C.S.of Md. restored the cluster and it's beautiful but the gauge will read up near 240 when the engine is hot at idle on a hot day.

I am fairly clear on how the system works and this one seems to work correct except the very hot reading. The problem is either a bad ground at the gauge, a incorrect sender (old AC unit) or the needle is not installed at the correct position.

My question is when turning the key to on position (50*cold engine) how far to the cold side should the needle move left. This needle will move to the low side of 100* (maybe around the 1 in 100). If I disconnect the sender wire from the sender it may move a tick more to the cool side, I thought I saw it move more but really not much if any.

In the summer when I let this engine idle extended it will get hot 210-220 but the gauge reads 240. I can't help but wonder if it's the needle.

[Edward J.]

Re: 1963 Corvette Temperature Gauge

Tim, Do you have a IR gun to take a measurement at the water cross over at the intake? that's the first place to start, or you'll have to throw a parts store sender into the car. and see where you stand.

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Thanks Ed,

From my memory, the sender is the original out of my 67 Corvette so I thought that would eliminate that. I need to get my head wrapped around the issue again, I can get a feedback pot and vary the resistance on the sender wire to the temp overload spec and check the gauge.

I wanted to pick brains to see if I missed anything, I checked the resistance from a known ground under the dash and the temp gauge housing and shows zero or very low resistance so I assume the gauge coil that pulls to cold is OK.

I really don't want to pull the cluster out to replace the pointer and I have a hard time believing it's put on wrong.

Redundant question but are these senders different even during the sixties period from say the early sixties cars to later when they started using the shunt resistor across the gauge coils.

[Richard M.]

Re: 1963 Corvette Temperature Gauge

Tim, The documents(below from lbfun.com) has info which may help diagnosis.

Also note that the gauge is not linear and made to be more accurate within a certain input resistance(sender) range, which is near engine operating temperature.

Also, I don't have a wiring diagram in front of me at the moment, but if I recall, the sender wire passes through the bulkhead connector so if there is any corrosion in there it could affect accuracy.

Rich
ps Is the car running ported or full manifold vacuum? Seems it shouldn't get that hot at idle.

[Larry M.]

Re: 1963 Corvette Temperature Gauge

Thanks Ed,

From my memory, the sender is the original out of my 67 Corvette so I thought that would eliminate that. I need to get my head wrapped around the issue again, I can get a feedback pot and vary the resistance on the sender wire to the temp overload spec and check the gauge.

I wanted to pick brains to see if I missed anything, I checked the resistance from a known ground under the dash and the temp gauge housing and shows zero or very low resistance so I assume the gauge coil that pulls to cold is OK.

I really don't want to pull the cluster out to replace the pointer and I have a hard time believing it's put on wrong.

Redundant question but are these senders different even during the sixties period from say the early sixties cars to later when they started using the shunt resistor across the gauge coils.

Tim:

Wilcox website has an excellent writeup on calibration of the dash gage. Suggest reading it. Get a few resistors from Radio Shack (or elsewhere) and you can check it (dash gage) at various calibration points using the green sender wire in the engine compartment.

You can also run the car and check the sender calibration (resistance) with an IR gun and multimeter as the engine heats up. Get a 3 or 4 various measurements so you can plot the curve. Wilcox site also has this info, and/or it should be in the PDFs that Rich provided.

Larry

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Thanks Larry, Richard and Ed, the article helps and I will try to troubleshoot and see what's going on.

It's going to take lots of self talk to remove that dash again.

[Richard M.]

Re: 1963 Corvette Temperature Gauge

Tim I recently removed the FUEL/BATTERY gauge pod for repair without pulling the cluster. I removed the Headlight Switch, Hood Release, Rollup Switch and was able to jockey it down and out.

I'm thinking if you must remove the TEMP/OIL pod, you may be able to pull the IGN switch, Lighter, and the oil pipe.........Maybe.....without pulling the cluster.

Rich

[Chuck G.]

Re: 1963 Corvette Temperature Gauge

Hi Tim.


Not sure if this will help you. Took pictures of my 63 gauge. Works perfectly. The car runs at 180*.

With the key in the OFF position, you can see the position of the pointer. It's dead over the slash mark to the RT of the 100* mark.

When I turn the key ON, the pointer actually moves a bit farther to the left, maybe touching the last "0" in the 100 mark.

Tough to get a good photo with the flash.

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Thanks Chuck, I appreciate the pictures.

Here are two pics of this gauge, one with the key on and one with it off but the reading did not move. FWIW, this is with a fully charged battery, I really hope it's another inaccurate sender (at least for a 63 gauge).

[Chuck G.]

Re: 1963 Corvette Temperature Gauge

I'd agree with you about the sender with the key ON, but with the key OFF, your gauge points a lot further "left" than mine does.

That being said, to my way of thinking, that would make your temp read lower if you're thinking that the needle is not positioned correctly.

Chuck

[Richard M.]

Re: 1963 Corvette Temperature Gauge

Tim, I dropped a note to Bill Harrison with your issue.....here's his reply.

Rich,
The values for testing are:

340 ohms - 100
140 ohms - 160
90 ohms - 200
70 ohms - 220

Usually with just power and ground they are at or just below 100. With power connected and the sender grounded, they peak way high.
They are often not perfectly linear through the entire range.
I try to position the needle so they're right on at 200 and 220. That keeps you very close when it warms up.

He says at power up the needle should be at or just below 100, just like Chuck's, so I'm thinking yours may be off. But if your needle is too CCW at power up like in your photo, then it'll read even higher at temp if it's readjusted more CW.

Of course, at power up, connected to the sender, the actual engine temperature/ambient is a factor. When you power up what is the ambient temperature of the garage/engine? At cold/cool engine, I'd shoot the sender with a IR gun and put a ohmmeter on it for the actual reading. That may help diagnose if sender or gauge.

Rich

[Ken A.]

Re: 1963 Corvette Temperature Gauge

Tim, I dropped a note to Bill Harrison with your issue.....here's his reply.

Rich,
The values for testing are:

340 ohms - 100
140 ohms - 160
90 ohms - 200
70 ohms - 220

Usually with just power and ground they are at or just below 100. With power connected and the sender grounded, they peak way high.
They are often not perfectly linear through the entire range.
I try to position the needle so they're right on at 200 and 220. That keeps you very close when it warms up.

He says at power up the needle should be at or just below 100, just like Chuck's, so I'm thinking yours may be off. But if your needle is too CCW at power up like in your photo, then it'll read even higher at temp if it's readjusted more CW.

Of course, at power up, connected to the sender, the actual engine temperature/ambient is a factor. When you power up what is the ambient temperature of the garage/engine? At cold/cool engine, I'd shoot the sender with a IR gun and put a ohmmeter on it for the actual reading. That may help diagnose if sender or gauge.

Rich

Rich,
It's amazing how much misinformation is in this thread.
180=105 ohms per GM print. The above values are all slightly off. You cannot chart values using a pot of boiling water.
Ken

[Richard M.]

Re: 1963 Corvette Temperature Gauge

Ken,

Do you have a full list of temperature values to resistance? That would certainly help. If Bill's numbers are off I'm sure he would like to have the actual specs, as would all restorers. I've seen several documents and none seem to match.

It would also be good to know what the 2 dashes represent between the 100 and 180 degree marks. Since the gauge is not linear I've always wondered.

If this is privileged information, I understand if you don't want to post it up.

Rich
p.s. maybe I should stick to 435 horse Holley stumbling and exhaust hanger riveting.

[Ken A.]

Re: 1963 Corvette Temperature Gauge

Ken,

Do you have a full list of temperature values to resistance? That would certainly help. If Bill's numbers are off I'm sure he would like to have the actual specs, as would all restorers. I've seen several documents and none seem to match. Yes I have the print. All Bill has to do is buy the correct
sender.

It would also be good to know what the 2 dashes represent between the 100 and 180 degree marks. Since the gauge is not linear I've always wondered. Factory calibration check points. The low side means nothing with key off.

If this is privileged information, I understand if you don't want to post it up. Yes it is, cannot release.

Rich
p.s. maybe I should stick to 435 horse Holley stumbling and exhaust hanger riveting.

No you're a good resource for this forum. BTW, the OP should contact Brian Tilles direct as he's a good guy & will help him
with his questions.

[Larry M.]

Re: 1963 Corvette Temperature Gauge

Ken,

Do you have a full list of temperature values to resistance? That would certainly help. If Bill's numbers are off I'm sure he would like to have the actual specs, as would all restorers. I've seen several documents and none seem to match.

It would also be good to know what the 2 dashes represent between the 100 and 180 degree marks. Since the gauge is not linear I've always wondered.

If this is privileged information, I understand if you don't want to post it up.

Rich
p.s. maybe I should stick to 435 horse Holley stumbling and exhaust hanger riveting.

Rich:

This is from the Willcox website. I mentioned it earlier to Tim.

http://repairs.willcoxcorvette.com/wp-content/uploads/2010/08/1956-1982-corvette-temperature-gauge-help-guide.pdf

Larry