oil Pressure & Water temp. gauges

D

dac

Junior Member
Oil pressure and water temp are the gauges I am trying to hook up. How do you hook up the two gauges to the electric and where does that connection occur? I am piggy backing the two together but then it needs to go to a power source that will only be turned on when the key is turned on. Thanks in advance. They are mechanical gauges.
 
IMHO, I would hook'em up by putting them back in the box and returning them to the store. The oiling system in the A does not produce pressure- the pump output fills up the valve chamber and gravity does all the oiling- in addition to the dippers on the conrods splashing oil all over the place. As for a temp gauge, I know people who have them who become mesmerized watching the temp go up and down as they climb and descend hills, worrying their car is overheating. You'll know when its overheated when it's steaming!
 
Oil pressure in a Model A engine will be about 6-8 pounds when first started up, dropping fairly quickly to about 3 as it warms up. I agree that an oil pressure gauge in a Model A can become rather boring to watch for lack of needle movement, but the one advantage I can think of is that it will tell you immediately if the pump has failed = the needle will drop to zero. It's probably too late by the time you notice that, unless you glance at the gauge every couple seconds. But when has a Model A oil pump really failed while driving, unless the screen becomes so clogged with crud that the pump can't circulate oil? Once again, though, that's got to be a fluke incident.
Marshall
 
If you have mechanical gauges then the only power you would need is for the lights. Run a wire from the tail light for power.
 
Bob C said:
If you have mechanical gauges then the only power you would need is for the lights. ....
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I agree. If they're mechanical they only need the electric to illuminate them- join the wiring into the tail light circuit if needed. However, on the original circuitry of the Model A there is no circuit which only becomes live with the ignition - so if you have gauges that are electrical , then maybe the way round that conundrum would be to fit a battery isolator switch - a useful thing anyway.
 
johnbuckley said:
I agree. If they're mechanical they only need the electric to illuminate them- join the wiring into the tail light circuit if needed. However, on the original circuitry of the Model A there is no circuit which only becomes live with the ignition - so if you have gauges that are electrical and then maybe the way round that conundrum would be to fit a battery isolator switch - a useful thing anyway.
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With a stock electrical system, the answer above is probably the only way. When key is turned on it merely grounds the coil, no power is activated. Your electric gauges require a hot wire to one terminal and the other terminal goes to each gauge separately. Don't expect much, or any, movement on the oil pressure ga. Have fun!
 
The small light bulbs used to illuminate the water temp and oil pressure gauges probably don't draw much current. If the owner wants them to be operated when the ignition key is turned on, the wires will somehow have to be incorporated in the ignition switch head circuit. This would not be a problem with aftermarket switches with contacts exposed on their backsides. Just connect the wires to one of those two terminals. But how would you do this with the original "theft-proof" popout switch? Would you run the wires to the ignition coil terminal post (+), which is where the lone wire from the original switch head is connected?

When the electronic ignition modules first hit the restorer community in the early 1990's, some of us found how the hard way NOT to run accessories such as an electric fuel pump for downdraft carburetors directly to the ignition switch. I fried an expensive module doing that. I don't recall the solution people came up with, but it entailed hooking up such accessories not directly to the switch, but to an intermediary device. My point relating to the topic under discussion here is: Will hooking up those two gauge light wires directly to the switch cause likewise problems, or is the electrical draw too small to mess things up? 'Something for the poster to consider.
Marshall
 
It would depend on how the car is wired— on a stock original car it would interfere with the points because the ignition switch is connecting the points to the coil.
 
For your information, this picture shows how to rewire an A for everything to operate through the ignition switch. I have an electronic oil/temp gauge on mine and have it wired this way.
 

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This is a toss up question. If the car is 12volt neg ground I'd use the electric gauges. If it's still 6v mechanical gauges are the way to go. I'd only install a water temp. There is a single bracket that fits below the speedo and looks like it belongs. As others have said monitoring oil pressure is not critical. You'll want to find a gauge that reads 20 pounds max just so you can see the needle move. Most new gauges are 60-80 pound. I've seen gauges screwed into the oil galley on the right side of the block. I'm going to do that when I finish the restoration of my old MotoMeter oil gauge.

My temp gauge is boring to watch. With my Brassworks pressure radiator, thermostat and plastic fan it's always glued at 160. It might be fun though to watch a passenger worry about the imminent explosion under the hood watching you drive around with 3 pounds of oil pressure on a 60 pound gauge.
 

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No, I run a stock 6 volt positive ground system. It has been suggested on previous threads that if you run everything through the switch then you should add a relay to take the load and keep the switch from burning up.
 
Ayers1 said:
No, I run a stock 6 volt positive ground system. It has been suggested on previous threads that if you run everything through the switch then you should add a relay to take the load and keep the switch from burning up.
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I would not recommend running "everything thru the switch", just the items you want on when the engine is running.

And yes, run a relay if you have some high powered device.

Snyder's, and possibly others, have an ignition switch with an accessories terminal if you want to go that route.
 
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Y-Blockhead said:
Snyder's, and possibly others, have an ignition switch with an accessories terminal if you want to go that route.
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Don't rely on the usual parts store replacement switch. There is limited room behind the panel so you need the shortest one you can find.
 
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