A friend of mine bought a nice mildly custom 54 Chevy Pickup. Beautiful paint and well put together with a straight 6 235engine. He is having trouble with the gauges and I went over to see if I could help but I have limited knowledge without having putting in the wiring myself. Here is what I found: The wiring is an EZ Wiring harness. The alternator is a 12 volt and it has a 12 volt battery. It is charging fine. The gauges seem to be stock. The temp gauge pegs out to hot side after about 1.5 miles. The engine does not get hot nor does the radiator boil over. The Fuel gauge pegs out to full. He ran out of gas thinking the gauge was correct. The gas tank is behind the seat like the originals. The Amp meter at idle shows the needle to be in the middle but as soon as you give it gas, it drops to the D disharge side of the gauge. The oil pressure gauge is the only one I found to be okay but that is a pressure gauge and only has an instrement light. There may be more variables than I am seeing. I do know that the temperature sending unit threaded stud where the wire goes, rotates. I don't think it is supposed to do that. Do any of you wiring gurus have an idea of what is going on? Since I don't know if the gauges were converted to 12 volt, could it be they need some kind of voltage reducer? I would appreciate you all's input.
The original temp gage was mechanical, it had a tube connected to a bulb in the cylinder head. Is the new one electric?or what? The gas gauge will read over full if there's an open circuit in the wire to the sender, or the sender is bad, or the sender is not grounded. The ammeter may be wired backwards, or it may not be charging. Since you say it's charging fine, it's probably wired wrong. These problems are pretty typical, gauges are complicated things to figure out.
The temp gauge is electric and hooked up to a sensor in the head. I dug up my gauges from my 1953 Chevy p/u and you are correct, the original temp gauge is mechanical. I will double check the alternator to make sure it is charging. I didn't have a way to check it today. The fuel gauge is fairly straight forward and I will have to get the owner to pull the seat out because it won't slide forward. Thanks for the suggestions.
Since the gauges are six volt units wouldn't there be a need for a method to get the proper voltage to each one of the electric gauges? I know I did ten years ago when I rewired a 49 Ford with a stock dash. Here is an Amazon link to an example, seems like I paid less than half the current price. https://www.amazon.com/Gauge-Reduce...olt+to+6+volt+resistor&qid=1691633946&sr=8-14 here is a little more info that I found.... For the electric gauges you need to get the voltage down to six volts so they will operate properly, this thread may help answer some questions. https://www.jalopyjournal.com/forum/threads/wiring-gauges-in-my-12v-conversion.601318/#post-6732911
I got the fuel gauge to work today. The float in the sending unit was jammed against the side of the tank. Who ever installed it did not check, therefore it always showed full. I flipped the float around and it went in like it is supposed to. Now it is funtioning. I hate working on stuff that someone else put in. After crawling under the dash, I found that the gauge cluster is an aftermarket set. I couldn't find who made it but it is not a GM product because each gauge can be replaced individually unlike an original that the housing has to be seperated from the front glass to get to each gauge. I am suspecting that it is a 12 volt cluster of instruments since the rest of the truck is functioning on 12 volts. I tackled the temperature gauge next. Since it is an electric sensor, I had the owner replace the sensor on the engine. The one that was in it was suspect because the stud where the wire is mounted, was loose and you could turn it 360 degrees. The new one does not do that. Anyway, I started the truck and the needle started moving as it is supposed to do but it eventually pegged out at hot. I put my hand on the radiator and it was barely warm. I ran out of time to continue on this today. Do you all think that the thermostat was put in backwards and not opening? I am thinking of pulling it out anyway and running it without a thermostat to see if the gauge settles down. I also checked the alternator output and it was charging about 13.5 volts at idle. The ammeter is still going to discharge when I advanced the throttle. What would happen if the gauge was a 6 volt gauge and it was getting fed 12 volts?
The ammeter does not care how many volts it has. But if it's wired up for positive ground, it will read backwards on a normal negative ground 12v system. It also needs to be connected to the right place, that can be confusing. The temp gauge...each type of gage requires a specific sending unit, did you make sure what type of gauge it is so you can get the proper resistance sending unit? If not, then it's probably just the wrong sender.
I had a 1951 truck with a 235 and it would heat up to over 220 degrees then cool back down to normal. It turned out to be the heater hose fitting on the thermostat housing being clogged with rust. The heater is used as a bypass on the old trucks. Once cleaned, the truck warmed up normal. Check the thermostat first and then check the heater hose and the fittings.
Thanks. I learned something new today. Like I said, I don't mind working on a wiring problems if I did the wiring or know the person that did the wiring. This truck has passed through 3 other owners. I will keep working on it next week.
That is some good information about the heater used as a bypass. Both heater hoses have shut off valves inline to keep the water from going into the heater core. Texas is 105 degrees right now so he has them shut off. I am going to tell him to open the valves and see if that makes a difference. This is a gorgeous truck with suttle changes. I crawled underneath tracing wires this afternoon and was pleasently surprised that it looked like new underneath.
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