Since I completed restoration of my 1934 Hudson 8 CV ten years ago, one issue that has remained unresolved is the inaccuracy of the GAS, WATER and OIL gauges. For those unfamiliar, each of these three "fluids" have floats (in the fuel tank, radiator fill neck and oil pan) that are connected to gauges in the dash cluster.
The GAS gauge reads approximately ½ when the tank is filled dropping to the "bottom line" on the gauge when approaching a true half tank remaining. The needle on this gauge has never read more than ½ full (or ½ empty for those that are a pessimist!).
The needle on the OIL gauge sometimes moves when I first start the car however, rarely reads full - even after a complete oil change and as shown "FULL" by the dip stick. Once the car is started and running, the needle disappears off the face of the gauge (past the "E" mark on the left of the gauge face). Two oil changes ago, I removed the float from the oil pan, manually moved the float arm through the full range of its movement and the gauge needle responded exactly as it should - from left ("E") to right ("F"). I reinstalled the float in the oil pan, refilled the pan with oil however, the dash gauge still did not work. I was suspicious that the cork float may have lost it's "float" as I'd shellacked it when I restored the car so, replaced the cork float material with modern material that I verified floated on oil. The new float material did not make any difference and the needle on this gauge still reads E (except for the random movement occasionally just when cold starting the car).
The needle on the WATER (coolant) gauge behaves much like the oil level gauge. It sometimes flutters a bit when the car is first started and then the needle disappears off the bottom of the gauge face past the mark.
Additional info...
> The car has a complete new wiring harness (from YnZ).
> No burnt or nicked wires... no smell of burned or shorted circuits.
> No fuse failure indicating a short circuit.
> Fluid levels (gas, oil & water) are at correct levels
> I have checked grounds under the dash to each gauge - all read OK.
> I have checked the water and oil sending units and no shorts between center stud connection and the radiator/oil pan (I have NOT checked the fuel gauge sending unit as it's a challenge to access).
> All electrical connections on gauges and sending units are clean and tight.
> All other lights, horns, the red A & C dash jewel lights, radio etc. work perfect.
> These gauges were not rebuilt when I restored the car but came from a reasonably complete 47K car.
> Car IS 6V Positive ground (as from the factory).
Any ideas on next steps to diagnose the problem??
Hudsonly,
Jim
Jim, have you tried connecting a ground wire to each sending unit (attach to a mounting screw). Also ground each wire from the sending units and turn the ignition on and see if you get full gauge response. (Don't leave ignition on for long, just enough for the gauge to register full. ) Good luck,
Geoff
I don't think Hudson went to the positive ground until 1936. I know my '33 is neg ground and I believe '35 is too.
Hi Geoff, I have not tried grounding at both the sending unit and gauge. Will try it this weekend and let you know results!
Thanks!
Jim
Jerry,
My original Hudson mechanical procedure manual states Positive Ground in 1934... (as well as 1935).
Thanks,
Jim
Jim,
Geoff's suggestion can be tried for testing purposes by making a very good connection to each sending unit's ground connection, then connect all these grounding wires together and attach them to the positive (grounded) terminal of the battery. I am looking now at the back of a 1934 Hudson instrument cluster and speedometer that I have. I see that a supply wire connects the three gauges, and then goes to the ignition switch. There is no ground connection at the gauges. Each wire from its sender partially grounds the terminal of its gauge depending on the resistance of the sender, as determined by the level of the fluid. You might connect a small bulb, or a meter, to the supply wire and to the ground terminal of the battery, to be sure that the gauges are getting full voltage. For example, assuming that the ignition switch has a separate terminal to supply the gauges, it might be faulty. Newer Hudsons have a voltage regulator that supplies the gauges. If such a regulator was added to your car, it could be defective, and not supplying proper voltage, which would be indicated by the test light or meter.
Recently I worked on the gauges of a 1986 Jeep that is used for plowing. The only gauge that was reading reliably was the ammeter. The fuel gauge would only go up to a quarter when the tank was full. The temperature gauge was unreliable. The oil pressure gauge didn't read at all. Finally I removed the gauge cluster (thankfully quite easy to do on this vehicle). The terminals were all tight. I took them apart completely, and discovered corrosion, including on the part of each terminal that was inside the cluster. By cleaning them thoroughly I was able to get all the gauges working properly.
So, if the tests that are mentioned above don't find the problems, try investigating the terminals on each gauge.
Per
Update... I have tried adding ground straps at the water and oil sending units and at the instrument cluster gauges - no change.
I rechecked wiring to the gauges VS the factory wiring diagram and wiring chart provided by YnZ with the new harness installed a dozen years ago. Connections are correct, clean and tight. I have not removed the gauges to check for internal corrosion (this maybe the next step?).
Measured the voltage at the terminal on the ignition switch/coil unit (this car has the ignition lock/coil combo under the dash) and with the car not running but key in "on" position, reads 6.4 ~ 6.5 VDC.
As I think I mentioned in my initial post - the water gauge sometimes gives a reading however after a couple minutes the needle goes back to the bottom of the gauge. Today I observed that when the ignition is first turned on, the water level gauge needle seems to flutter around a bit (its at the very bottom of the gauge - so, tough to see). After approx 10 seconds it starts to climb and give an accurate reading. I couldn't run the car today as I'm doing some carb work also but, in the past after 2 or 3 minutes running, the needle on the water gauge disappears.
Does anyone have hints on how to test (an possibly calibrate) these gauges? Anyone in the club experienced at repairing them?
Jim
Jim,
It is good that you have normal voltage being supplied by the ignition switch. I assume this voltage is also at the supply terminal of each gauge. You can try briefly grounding the other terminal of each gauge, while watching the gauge. The needle should move across the gauge. If any of the gauges doesn't move, I think the next step is to take that gauge apart.
The charge light and oil pressure light depend on the instrument panel being grounded, but the gauges are not grounded at the instrument panel. I'm confused as to where you have put ground straps at the instrument cluster gauges.
Per
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