MassVette

Been going through all kinds of heating 'events' with the 'vettes.... First, the fan relays melted on the ZZ/502 (that's another story), then the new GM 454 HO Mark VI we installed in the '67 ran at 210 on a cool day, up to 250 on an 85 degree day!
Having installed all new components in the '67, I found this hard to believe, but have since limited the driving to cool days.
A friend of mine suggested we test the actual operating temp. with his digital infrared gauge, so we did. the temp at the sender read 155, while at the gauge read 210! Subsequent spot readings of the radiator, hoses and block confirmed the discrepancy. Anyone have an idea whether the culprit might be the gauge or the sender- or both? Thanks.
P.S.
I'm kinda getting sick of replacing parts- I'd like a little uneventful driving to make it all seem somewhat worthwhile!
:yesnod: :chevy :chevy :yesnod:

stouro

Hey MassVette,
I'm just now working this out on my '62 vette. Infrared Thermo
says 174 and the gauge says 245 with a brand new sensor. Thanks to the help of a couple of guys on foruma and an Electrical Engineer friend of mind
I think the problem will solve. I'm told that I should add a resistor in series
with the gauge to calibrate the gauge to "normal" temperature, in my situation
the resistor I need is a 47 ohm 2 Watt resistor. You can experiment with
anywhere form a 20 ohm to a 68 ohm resistor until you get the proper
reading. Also make sure that your terminals on the sensor and gauge are
clean (no corrosion). I polished them with light sandpaper and put silicone
dielectric grease on the connections. That should get you back in the ball park.
mine was off by over 70 degrees. My guess would be try a 33 ohm resistor first.
Good Luck,
Shawn :chevy

TheOman

There is no end of posting about thisand I believe that indeed it is correct. Seems likley that your sender is at fault. At minimum it is contributing to the problem. For whatever reason the aftermarket cannot seem to make a senders that properly sends the right message to the guage head. I have actulally considered putting a regular old mechanical guage in the car someplace or other to tell me the correct number. I hate seeing that guage creep up too high and if it is wrong I could just glace at the mechanical guage as a sanity check.

There are ways to put a resistor in the wire that runs to the guage and therby lower the indicated reading on the dash. Apparently this method is not accurate over the entire range of the guage reading but at least you get closer to a true reading. Lots of the members have posted on this so if you want to "tune" you guage with the existing sender via the in line resistor method you should be able to search out the posts.


[Modified by TheOman, 7:57 AM 4/25/2002]

MasterDave

Since your two vehicles (and mine) are not stockers, why not do what I did? I installed a new sender, gage and wiring harness and got way too frustrated trying to make the darn thing work. :mad I just installed an aftermarket parabolic gage under the dash and now I get a true temp reading even with the key off.

kellsdad

Try this thread: http://forums.corvetteforum.com/zerothread?id=265820

Kid_Again

...whuzza parabolic gauge???????

MasterDave

No wires (except for the light). Copper one piece tube filled with something, dunno what, with the sending unit built into the line. Simply screw it into your cyl head, run the copper line to the gauge and screw it in. Gives exact readings every time key on or off. Got mine at B&B or Schucks, they're everywhere. Under $20.

MassVette

As usual, this forum has the answers. You guys are the BEST! Thanks !

MasterDave

You're welcome. I put mine on the left side of the steering column under the dash. There was a small hole there already, I just used it. Also the unit I bought came with a bezel which could be turned or angled so I could adjust the gauge for best viewing. Later...

nolandadams@d-web.com

There are a lot of little problems with the stock temperature gauge on 1967 and older Corvettes. For example, the sending unit must be properly grounded in the intake manifold. The single contact sending unit uses this as an electrical path and too much teflon tape can insulate the sending unit. Make sure it's grounded, and some of the problems will go away.
-Noland Adams

62fuelie

Autozone sell a sending unit for six bucks that usually works well on older vettes. It is a Wells model TU5. Approximately 700 ohms @ room temp. No resistors or fancy circuitry needed. Looks like the Delco unit, but has no markings. :D

4_inch_Bore

"Autozone sell a sending unit for six bucks that usually works well on older vettes.
It is a Wells model TU5. Approximately 700 ohms @ room temp. No resistors or
fancy circuitry needed. Looks like the Delco unit, but has no markings."

I was about to post the same thing. I got the same unit, except it was $4.79. I even used some non-hardening sealer. Works fine.


[Modified by 4_inch_Bore, 10:24 PM 4/28/2002]

MassVette

I tried leaving off the teflon on the lower half of the new Wells TU-5 sender I bought at Auto Zone;
PROBLEM SOLVED!!
Again, thanks so very much for all the help. I do appreciate it.
:yesnod: :chevy :chevy :yesnod:

62fuelie

Autozone, or Wells or someone owes me some royalties for all the free advertising I've been giving them. :D