constant voltage regulator
How do I test them?
I know its been covered here before, but its buried in a thread somewhere.
I'm fixing gas and temp gauges. Neither work.
I installed a new regulator and still nothing..
I have two old regulators. One of them should work.
Or is there a common ground I should check?
Constant Voltage? Not really.
Nathan,
They test "best" with an analog volt meter, but I've used digital volt meters (DVM) too with OK results. The analog needle is "dampened" and does not react as fast to changes as digital, so a DVM will see higher spike voltages than an analog needle can physically accomplish. More on that below.
How they work: They are a bimetalic "heater" switch and the idea was to alternate the voltage/current on and off again at a rate that never let it reach a full 12 volt output. Very crude, but apparently worked. Internally one side is a fixed point contact. The other contact is at the end of a bimetalic spring. When the spring is cold it closes the switch - full voltage at the two terminals (12 volts in, 12 volts out). But when it closes the switch and current is flowing this very quickly heats the bimetalic spring which causes it to move in the opposite direction of closed to open the switch - zero voltage. The spring now cools again, closes, full voltage, heat, open, cool, close, rinse, repeat - on/off/on/off. The average on-off voltage created (though seeing 12 volts) is about 5 volts.
To test: ground the body to -12 volts and apply +12 volts to the input terminal. Measure the output (body ground to output terminal). With an analog volt meter the needle swings from 0-5 volts (+1/-0). With a DVM the reading will be higher than the 0-5 volts. The digital reading is more reactive so you will see slightly higher than the 5 volts +1 reading. I saw up to +3 (8 volts) using a DVM. You'll see a "glued-in-place" screw that originally set the bimetalic spring tension to get the on/off cycle just right; this to make it output the 0-5 volts.
Suffice it to say this design is VERY FRAGILE and any attempt I made to adjust them (if they worked, but gave the wrong reading) or look inside one and make a bad one good (there is a set of contacts inside that wear from the constant ON/OFF cycle) and so my final analysis of them is - if they work, great. Otherwise they are trash.
I did pick up a few of the solid-state versions they offer now and put them in various cars I've touched of late, all with great results. They cost a little more, but will last a long time. Transistors can handle this switching action quite readily. I did find a site showing how to make them too, but I've not got around to making any, though I did get the parts to do so.
Real Soon Now.
Good luck!
Constant Voltage Regulator (CVR)
I think with the DVM you should shoot closer to an 8-volt reading as I saw with them.
I don't know the math that says what makes things read what; like, does the higher CVR setting make for higher or lower gauge readings. I didn't want to play with working units (at the risk of breaking them) to find that out. I do know most senders have a pretty reliable resistance reading range when new.
The new one... was it solid state? I think most being sold today are , whether they say so or not. Can't prove that, but such a no-brainer to use a transitorized 5-volt regulator and solder it in a can than to make that fine-wire heater wrapped around a bimetalic spring doo-dad. The transistors cost all of $.50 to buy (I think I paid $.10 a piece for mine on-line). Shipping cost me more.