'67 Temperature Sending Unit

[Patrick T.]

I've checked the archives, but the question still remains, does GM offer a replacement sending unit calibrated for a 180 degree engine and gauge? The one I bought from Zip now has my temp gauge reading 200-210 and I know this isn't right.

A few years ago I bought a new GM ZZZ crate engine for another Vette with the sending unit already in it, with a 180 degree thermostat; the temp gauge was right on the money at 180 degrees. I can't understand why this one worked OK and over the counter GM replacements don't, or at least the one I have now.

I've also read a while ago about installing an inline resistor on the sender "send" line, before the temp gauge. Has anyone found out what the the "magic" resistor value is? Seems that they would all need about the same correction factor. Thanks. Patrick

[Ed Jennings]

Re: '67 Temperature Sending Unit

Patrick, apparently all the GM units are off. You need to find one that reads about 700 ohms a room temp. As I'm sure you've already read, there are aftermarket senders readily available that will give a fairly accurate reading with most gauges. Keep in mind that if you substitute a resistor in line for an accurate sender, the gauge will only be correct in one fairly narrow range. If your engine should overheat, you need to know it immediately. There are some vendors who offer "relcalibrated" senders. I have no personal experience with any of them, so cannot comment.

[Joe L.]

Re: '67 Temperature Sending Unit

Patrick-----

If you find an NOS GM #1513321 sending unit or anftermarket NAPA or Standard Auto Parts TS-6 unit, I think that your problems will likely be over.

[Patrick T.]

Thanks Ed and Joe! *NM*

[Duke W.]

Re: '67 Temperature Sending Unit

Ed reported on 10/19/02 that the Wells TU5 sender has a correct calibration. Is this the same part as the NAPA/Standard TS-6.

Duke

[James W.]

Re: '67 Temperature Sending Unit

I recall someone saying that you should not use any sealant on the unit such as tephlon tape or the tephlon paste. It was said that this will make it read incorrectly. Is this correct? What type of sealant is reccomended?

Regards,

James West

[Patrick T.]

Re: '67 Temperature Sending Unit

Duke, I found out that Long Island Corvette Supply has the new GM replacement senders which have been recalibrated to 180 degrees, so I bought one.

[John H.]

Re: '67 Temperature Sending Unit

Patrick -

Do you have an I.R. gun to compare the temp of the thermostat housing to your gauge reading? I'd be interested in the correlation with the new "calibrated" sender from LICS.

[Leonard Gionet]

Re: '67 Temperature Sending Unit

I have a 1966 BB that tends to run hot according to the temp guage. I would like to check accuracy. How do I find and buy an I.R. Gun?

[Jack H.]

Re: '67 Temperature Sending Unit

While an IR gun is the GREATEST temperature tool you can have in your crib, it's probably 'overkill' to buy one for a one-time investigation. Almost EVERY tech involved in HVAC work has one a 'loan' to get a one-time reading can do the trick. Good ones run $100+ and feature functions abound (dynamic range, distance to source, 'focus' considerations and accuracy).

To get a simple 'second opinion' that's pretty darn close to reality, you can 'poor boy' the task.... Shut the engine down, use duct tape to wrap the sensor probe of a conventional oven meat thermometer to the back/lower side of the upper outlet hose being CAREFUL to insure it's held firmly in place and AWAY from rotating assy's (read that as the fan and various belts).

Now, start the engine and let it come up to speed and reach steady-state thermal equilibrium. The thermometer is going to be pretty darn close to giving you an accurate reading on exhaust coolant temp! Last, remember underhood airflow was designed for closed hood operation.

You might see a difference between actual readings with the hood open/car stopped vs. hood closed/car in motion. But, for checking the accuracy of the dash gauge, absolute temp isn't the issue--it's relative temp you're after (specific coolant temp vs. dash gauge reported temp) and either a thermometer or IR gun will get you there!

[Gary J.]

Re: '67 Temperature Sending Unit

I was thinking that the sending unit from LI you had to put a resistor in line. I thought I read that in their catalog.