The Stovebolt Site Forums The Shop Area Interiors Instrument gauges testing '46 Chevy 1/2 ton

Got a bit wild today and decided to try restoring the gauge cluster myself. Need feedback on testing methods and results received, please.

Took it apart, cleaned pieces and tried testing each gauge. But, don't know if the reading obtained indicate each gauge is good or not.

For the speedometer a cable was attached to a drill. It read, at full trigger, about 30mph. Good or bad?

Temperature gauge: Water was heated to boiling, the gauge bulb sensor was immersed. Note, by the time the test started the water had cooled to no longer bubbling. Gauge read about 15 degrees higher than either the analog or infrared digital thermometers, used to cross check readings, I'm thinking this one needs replaced?

Gas gauge: Ohm meter readings fluctuate between about 34 and 40.
Is it good or bad?

Battery gauge: Ohm meter readings fluctuate between 1.4 and 2.0.
Is it good or bad?

Oil gauge: used a bulb syringe to launch a puff of air. The gauge read 15 pounds. Good or bad?

What should each of these be reading?

Is or are there better ways to test these gauges?

Starting from the top,
If the speedo needle moved smoothly and didn't bounce, it's likely fine.
+/- 15 degrees on that gauge is probably well within the original spec.
Test only tells you the winding is intact. connect it in series with a good gas tank sensor or a variable resistor of the same range as the sender and a battery. Changing the resistance should move the gauge in scale.
If it is a volt meter attach it to a battery and check the reading with another volt meter. If it's an amp meter, connect it between a battery charger (set for less than the scale of the gauge) and a battery and check the reading.
oil gauge sounds about right, but checking with a calibrated pressure supply would be more accurate.

Jim,
Check out this article about the gas gauge.
Harold

Thanks guys. I'll do some more checking.

I need some guidance on my speedometer. Not reading at all moving down the road. My first test was to hook the cable to a drill. The drill moved the gauge but it was bouncing as much as 15 - 20 MPH. Based on the previous comment I guess this is bad? I was assuming this was not a problem and believed the problem was the speedo gear in the transmission that drives the cable. (It could still be bad also because there is zero movement while driving the truck) Is a bouncing speedometer repairable (by a total amateur with good mechanical aptitude) or does it need to be replaced. I have changed the plastic gear in a transmission on am automatic transmission in a 72 olds before but a lot of the post I have seen on the subject here suggest matching the gear could be a challenge.

See if this will help you.
Harold
Speedometer Repair

I didn't read all the link Harold46 posted but I know from experience that they will "bounce" but will stop and run smooth if lubricated. I hope your fix is that simply.

I will try lubricating the cable first. If that does not work I will probably try the repair/refurbish as outlined in the link Harold46 provided. That looks more like a winter project at the bench and a lower project compared to the other items on my list. I am anxious to finish some of the other repairs to get it back on the road for a few cruise in's and back road drives this summer. Thanks for the tips.

this forum is awesome just joined today.

Regarding the Ammeter test above. I tested the one Sparky came with using the steps given in another thread in the SB.

To recap that: Used a wire lead fixed to a battery, with the other end alligator clipped onto one terminal of the ammeter. Used a test light attached by the clip to the other gauge terminal. Used the pick end of the test light to touch the other battery terminal. The test light glows, but there is no gauge movement.

I tried 2 other gauges, both new old stock. Results were the same. Is the test process incorrect?

Thanks

Use a bigger bulb like a headlight. Should see amp draw (movement) in one direction on gauge. Reverse terminals on gauge, should see movement in other direction on gauge.

Hookup Example: (which you did correctly) Bat + to gauge Term 1, gauge term 2 to bulb 1, bulb 2 to batt neg. Don't use the pick test light bulb this time.
Whatever you do, just quickly touch don't clip it on both battery posts.

The fact you tested several and got NO reading is confusing to me. All I can think of is you need a bigger test draw (bulb). A super small fraction goes thru the windings, the rest is shunted. Gauge tolerance not reading a pee wee bulb draw.

Ok thanks. I wondered too if the alligator clips used for the test connections maybe we're not making a sufficient contact. I'll try a headlight.

If the bulb was lighting, you had contact.

Good news!
Using a headlight in the test circuit, instead of the pick/test light worked. All three ammeters tested good.

It appears the pick/test light was the problem.

Maybe this learning adventure will help others too?

Thanks to all that helped.

Speedometer rebuild completed today...yea!!! Took a while to get it thru my thick head on some aspects, but the Tech Tip in the Stovebolt was a tremendous help. A test with a cordless drill seems to indicate all gear alignment and assembly was good. There seemed to be a few minor differences between the GMC gauge used in the TT vs the '46 Chevy, but once I understood the concept all worked well.

A suggestion on removing the needle someone offered in another forum, don't recall who or where or I'd give them credit, recommended using a stout dinner fork. That instead of a screw driver. Working the tines under the needle and protecting the dial face from scratching with a piece of paper or tape worked very well.

If taking the odometer back to zero is desired, align and start each decal at the "o" marked on each wheels right side.

Using a 10 penny nail to hold the odometer stack while going thru the cleaning, decal placement and checking gear alignment was helpful too.

The deteriorated grommets used with the screws holding the spring assembly to the rest of the speedometer case were replaced using rubber vacuum hose cut about 1/4 inch in length.