1963 Corvette Temperature Gauge

[Richard M.]

Re: 1963 Corvette Temperature Gauge

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.

I try, but sometimes I get in trouble....

I guess maybe Tim wanted to do some research and get some baseline opinions before jumping on the phone.

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

Hmmm, sorry I missed that Larry, thanks. Interesting what Paragraph 2 says about the Delco Chart. He says they were wrong?

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[Timothy B.]

Re: 1963 Corvette Temperature Gauge

OK, I went outside today and garage probably 55-60*. I checked the ohm's on the car sender with my digital ohm meter and it read 1,087 (something like that) ohm's. Maybe that's why that gauge is moving so far CCW. I double checked this from the tip of the sender to sender body and then from tip of sender to ground on upper A frame and it's approx the same.

I also agree with the coil pulling so far CCW it's hard to imagine it would read so hot.

Think about this for a minute, I have (5) 15 ohm radio shack resistors soldered together so I should have 75ohm's and when I connect them between the sender wire and engine ground, the gauge reads near the mark between 180 and 240*. I guess this mark may be considered approx. 210*.
If I take my ohm meter and re-check resistance from good ground to sender wire clip with these resistors in the above arrangement, the meter only reads something like 38ohms when everything is hooked up. What am I missing here, does anyone know what would happen if the wires are crossed at the gauge plug. The light green wire powers the fuel gauge coil and fuel sender plus the brake warning light and everything seem to be fine unless I installed the plug on the gauge wrong (if that can even be done).

[Richard M.]

Re: 1963 Corvette Temperature Gauge

Tim, As long as you didn't remove the terminals from the plug and got them reversed, I'd say no, you can't reconnect the plug wrong.

If you are reading 38 ohms when your 75 ohm resistor is in series in the path, then you're likely putting 75 ohms in parallel with the meter resistance, yielding 38 ohms. With the plug off the back of the gauge, put your ohmmeter on the S terminal of the gauge to ground. You'll read a value that will be the coil resistance. I just did this recently on a '63 fuel gauge and it's 160 ohms. Not sure what it is on a TEMP gauge.

I just did a quick review of my Ohms law....

R Total = R1 || R2 = (R1 x R2) / R1 + R2

To find R2, which in this case is the meter......

R2 = ( R1 x R Total) / ( R1 - R Total ) = ( 75 x 38 ) / ( 75 - 38 ) = ( 2850) / ( 37 )

R2 = 77 ohms

So I think the S terminal to Ground (i.e. the coil) is about 77 ohms. Not sure what it is to Power.

Sorry this doesn't help your meter diagnosis, but this is why you're reading 38 ohms.......I think.

Rich
p.s. Rivets are easier.

edit.....
According to the Wilcox chart, they state 71 ohms should be the mark between the 180 and the 220, so your gauge seems pretty accurate at that 75 ohm value, give or take a few ohms.

[Duke W.]

Re: 1963 Corvette Temperature Gauge

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.

Let's get back to some basics.

1. What engine configuration?

2. Is it OE or modified?

3. What's the number on the VAC and does it work properly?

4. How about the radiator? Original? DeWitts OE replacement or something else?

A 327 with a properly functioning OE type aluminum radiator, properly functioning fan clutch, and a proper spark advance map should not get that hot after extensive idling even in 90-degree weather.

Duke

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Thanks again Richard and Larry,

I want to correct some info I reported in post # 17. Cold sender ohm readings are approx. 1,004 and the gauge today is right at the bottom of the 100* mark (even with the lower 100 writing), temps are 50-60+-.

At battery voltage with my 75 ohm's connected from the sender wire plug and good ground, the gauge reads about the width of the needle above (to the cooler side) of the 240* mark. It would seem that according to the Wilcox article 68 ohm's puts the gauge at 240* so this gauge and wiring may be accurate.

I am going to make another resistor approx 128+- and check it against the gauge to see if it gets close to 180* and if so I will be looking at the sender resistance at 180* engine temps to see how accurate it is.

Ken,

I would never want to call someone on the phone and bother them with something that may not have anything to do with the services they performed. This is a technical discussion board and we (most of us) are here to help each other from our experiences.

I am always learning and enjoy sharing with others in a effort to help.

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Let's get back to some basics.

1. What engine configuration?

2. Is it OE or modified?

3. What's the number on the VAC and does it work properly?

4. How about the radiator? Original? DeWitts OE replacement or something else?

A 327 with a properly functioning OE type aluminum radiator, properly functioning fan clutch, and a proper spark advance map should not get that hot after extensive idling even in 90-degree weather.

Duke

Duke,

It's my 63 coupe, 327/300hp 4.060, stock 929 camshaft 8* initial 15* V/A #201 all stock with Dewitts OEM replacement radiator, 13lb. radiator cap (307). The engine runs very nice but I have never shot the thermostat housing with a IR gun, extended idle on a hot day it will get hot according to the gauge. I can only recall one time when a small amount of fluid pushed out and it was very hot 90*+ and humid with extended idle and hood open inside garage.

[Duke W.]

Re: 1963 Corvette Temperature Gauge

Assuming that likely ancient 201 15 VAC still functions properly then you have the correct range of total idle advance.

IR gun readings are necessary to validate the accuracy (ballpark) of the temp gage. You will probably get more accurate readings by shooting the upper radiator hose, but also do the thermostat housing and radiator inlet.

The Harbor Freight IR gun I have reads about a 3:1 or 4:1 cone. So hold the gun very close to the surface you want to measure. If it's too far away it can pick up cooler or hotter backgrounds and give a sort of "average".

Also measure the exhaust manifolds (up close). They should be no more than about 500F if the VAC is working properly at idle.

Duke

[Timothy B.]

Re: 1963 Corvette Temperature Gauge

Duke,

I'm going to get a IR gun and double check engine temps but first I want to find a simple potentiometer to add resistance to the circuit and double check the temperature gauge and wiring. I have the steering column out of the car at the moment and want to verify the gauge/wiring before reinstalling, I will post results of my progress.

When C.S.of Md. did the cluster I replaced the main wire harness with L.L harness. Never any problems with anything except this gauge reading issue. When I removed the engine harness/firewall plug to check the connection I did find one wire that had the pin pushed back on the fuse block side. I pulled it out with needle nose pliers and felt it click in place, this wire (pin) was the black + wire that runs from the starter solenoid to ammeter and the gauge now deflects more when load is applied. Don't know how I missed that so I did fix something.

According to the Wilcox information the 63-64 gauge reads 180* at approx 128 ohm's and the earlier gauges read the same 180* temp at approx. 96 ohm's. If the sender is the same part # it's no wonder these readings are all over the place, 30+ ohms can make a big change.

[Duke W.]

Re: 1963 Corvette Temperature Gauge

I recall threads years ago that claimed a Wells TU-5 temperature sender gave more accurate gage readings. I was a little suspicious as I figure that device is the same part from the same plant in other brand boxes just like most "brand" points and other distributor parts are made by Standard Motor Products regardless of the "brand" on the box.

But there were enough guys reporting good results to make me believe it's worth a try.

You can probably find some of those threads in the archives.

Duke