Yesterday afternoon I finally took out Lady after 2 months of improvements...
All was well but the gauge cluster of the repro Rally Pac I got from the Parts Plce. It does fog up behind the lens like others had mentioned.

The worst of all is that "normal operating temperature" is indicated at almost full hot! I would assume it should be in the middle.
I know the engine is not running hot, as I can still hold the valve covers and touch the block for a short time.
Idling, 60mph, and heater on full blast caused the needle to fluctuate from HOT to the bar below. Max temp from the heater was only 150 degrees.

I am using a stock replacement sending unit (borg warner WT203) and it reads 100 Ohms (disconnected) and 6.11V (connected) at normal operating temp. I let it cool and took measurements along the way. The gauge middle line is 130 Ohms and 7.03V. A tad above 'C' was 320 Ohms and 9.4V. It does not seem to be a linear scale.

-- Has anyone ever took measurements of their sensors at different temperatures?? I need to see if it is the sender or the gauges.
Would someone be kind enough to take a few measurements?

I will call the parts place to see what they recommend but they will probably blame the sender, as it was not bought from them...... Hate to yank it out yet because I sealed it in so well...
I will borrow our lab's IR thermometer and see what actual temps are this afternoon. At worst I am hoping I can put a resistor in series with it to calibrate it to my sensor. OR maybe the gaude inside the cluster can be calibrated...

The oil gauge reads a little above the middle at the lowest idle and goes up a notch above; not too badly off.

I drove this car home through 98 degrees for over a thousand miles so if there WAS a problem, it would have surfaced already...

Any ideas?
Thanks!

 

Here is the data collected from the profile I performed last year.
I hope it can be useful to others. (Be sure to expand the picture to make sure it is clear to read).

After using the IR thermometer for these tests, I had found that my car was actually running hot when I installed the rally pack. It had only a 2-core radiator, which was plugged up some, and a faulty fan clutch.

So given that IR thermometers cost as low as 10 bucks from Harbor Freight, they should be in every car-guy/gal's toolbox!

Remember this is only a guide - what I got on my particular sending unit and gauge combo. Other combos may vary but should be in the same ballpark...

 

To calibrate your own gauge and sender combo, here is the procedure...

Create your own table like the one posted above. The current and wattage columns are not really needed.

You will need an infrared thermometer, volt / Ohm meter, patience, and a few UNINTERUPTED hours for this procedure.

The first step (and the fun one) is to run the car and get it as hot as it will get through some lead-footed driving.... Then park and pop the hood. Connect the negative volt/Ohm meter lead to the engine block with a gator clip for ease of measuring.

1. Take the car's temperature with the IR thermometer. Take 3 measurements right beside the factory temperature sender and record the approximate average. Generally you hold the IRT about 1/2" off the engine.
2. Pull off the wire from the sending unit and quickly record the resistance (in Ohms).
3. Put the wire on again, turn the key on (but do not start the engine) and wait until the gauge needle settles, which is about 10-15 seconds. Quickly measure voltage across the sender (with the wire on it). Turn key off and then make a note on where the needle is on the gauge.
4. Wait for the engine to cool about 10-15 degrees (as determined with the IR thermometer) then repeat steps 1-4 until the gauge reads below the COLD mark.

Find out what the resistance is at the gauge CENTER line. Using your new cal chart, determine what the resistance was at near your thermostat temperature. Take the resistance difference and add 1/2W resistors in series (or parallel) to the sender to get the gauge to read in the CENTER at your t-stat temperature.

Resistors and the temp sender act a bit differently, so it may take a little experimentation to get your gauge to read dead-on.

Once this has been done, repeat the cal procedure and make some notes what temperatures go with what gauge readings. This way, you will know the actual temps just by looking at the gauge. Either memorize it or make a small cheat sheet to keep in the glove box...

 

I just put a used Rally Gauge in my 1968 442 and the temp reads between center and full swing hot (one notch above center) at 'normal' operating conditions. Not sure the actual temp (need to get an IR thermometer and a new, know thermostat). Anyone have any experience w/original Rally Gauge calibration? Oil pressure is typically one notch above center also. I also installed new sending units, of course, for oil P and T (from BAP).

Thanks to all who provided info about wire connector modifications, especially the trick about removing the green GND wire from the ignition switch.

Speaking of ignition switches, to remove the tumbler, turn key to accessory position, insert paperclip into small hole next to key hole slot, gently pull while turning counter clockwise. Easy if you know how. Also, the molded plastic connector on the back of the ignition switch has 3 fingers. The fingers are barbed radially outward from the switch body. Use 3 jewelers screwdrivers (or similar) to press the barbs inward simultaneously. I used a large screwdriver to gently pry off the connector. That gives you access to the tang so the green GND wire can be removed without cutting it. It's almost as fun as removing the gauges...NOT.

 

My 70 442 uses a Lectric Limited "correct" sender.

At normal operating tempretures, the needle on the gauge stays planted on the first 1/4 hash mark.

The thermostat is a Robertshaw 180 degree high flow.

 

Having the same issue with a factory gauge pac 70- . I run the car and the gauge rises to full hot. I have searched the blogs here and I have not been abel to find what others did to fix this. Are others adding in a resistor. has anyone ever found the resistor on the back of the factory gauge pod bad?. What is resistor rating on the back of the gauge for the temp and oil gauge. Is there a sending unit that works....quick temp check with a meter, doesn't show the car is overheating ~ 180 degs...thanks

 

Update - temp sending unit I bought had a calibration/tolerance that did not work for a factory gauge. Replaced it with borgwarner unit, gauge is reading just below the mid point, works fine now.

 

If you have a part number for the BW part that did work, it would be very helpful for those having the same issues.
Glad you got yours working again!

 

buddy i had mine calibrated to the sending units it would be a good idea to get this right now the fall is almost completely here and this is the slow season for them. I have had no problems afterwards contact year one for the best service.

 

borgwarner wt203, worked for my factory gauge.

 

This is the same I used for the aftermarket RP gauges, so the repros must not have been calibrated from the factory.

 

which oil sending unit are you using.

 

B/W #S769 but I do not think this works withthe repros, either, as it usually makes the needle stay on full High except at hot idle, where it comes down a notch.
Do you know what works withthe factory gauges?

 

The oil pressure sending unit should be for 80 psi. Each quarter line is 20 psi. I am lucky that my originals are still working. For temp, the quarter line is about 180 degrees, and the middle line is 210 degrees.

Look at this sending unit http://www.ebay.com/itm/Classic-Inst...sories&vxp=mtr

 

thanks, I am getting a similar reading for the temp on my factory gauge with the wt203 so it appears to work with my factory gauges. For the oil gauge it runs in the middle when warm, but with rpm increase it will step up then back down with rmp decrease, sometimes I get a little flutter. Checked PSI and she runs at 35-40 psi warm at idle, no issues.
When you raise the rpm, does he oil gauge needle on your factory gauge gradually raise or step up..? thanks

 

I have noticed that some factory gauges work well, and others have small problems.

And to answer your question. Yes, when I raise the RPM, my oil pressure raises as well.

 

I think this winter I am gonna pull my repro gauge cluster and see if there are any trimm pots inside. I need to make the thing somewhat accurate...

 

thanks,.Found feedback on this same issue on a different car site. The car had the flutter issue and the gauge needle moved in steps. The new replaced sending unit was the issue in that case, and I suspect it is in my case as well. I think I will return mine, and find an ac delco unit. Maybe that one will be a better calibrated/design for the factory gauge.

 

Reviving this old thread on purpose.

With the temp sending gauge, what causes the gauge to spike to full H (hot) when the key is turned to 'Run' just prior to starting? Once the car starts the gauge drops to C and then works it's way up to temp. Is this a wire that needs to be truncated? My car came from the factory with idiot lights and now I've installed the rallye gauges.

 

This is a copy of a post from another thread below (post #14):
https://classicoldsmobile.com/forums...-wiring-75378/

 

Thank you Eric,
Going a step beyond that, from that same thread but post number 22, this question was never answered