140 temp gauge wonky

The original regulator also gives it a shot of 12V when first switched on, just so the gauges jump up toward their readings, without that they'll still get there, just slowly.

JohnMc said:

The original regulator also gives it a shot of 12V when first switched on, just so the gauges jump up toward their readings, without that they'll still get there, just slowly.

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Are you sure about this?
Never heard or saw any documentation of that behavior in the green book.

A mechanical regulator depends on the heating of the coil around the contacts to open and close. So when first turned on. The coil isn't warmed up so the contact passes the appliced voltage to the circuit. Then the coil warms quickly and starts opening and closing the contacts to regulate the voltage.

With the LM7805 it will rise slowly like in a 240 which uses an electronic regulator in the 81 and newer dash setup. Function will be fine.

dl242gt said:

A mechanical regulator depends on the heating of the coil around the contacts to open and close. So when first turned on. The coil isn't warmed up so the contact passes the appliced voltage to the circuit. Then the coil warms quickly and starts opening and closing the contacts to regulate the voltage.

With the LM7805 it will rise slowly like in a 240 which uses an electronic regulator in the 81 and newer dash setup. Function will be fine.

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Disclaimer - I'm no electronics genius, so take this advice however you'd like - when I had to deal with a possibly dead voltage stabilizer (not regulator!), I used a digital volt meter. It seemed to indicate that the way the original one (as pictured) works is not by changing the 12 volts to a constant 5.1 volts, but, would continuously pass 12 volts (for a very short amount of time) and then 0 volts (also for a short amount of time. In this way, it would provide an AVERAGE of 5.1 volts, but never did it seem to actually provide 5.1 volts. Because the gauges are very slow to respond to their input, you never see the change due to this on/off cycle. Because of this, the "update it to a modern regulator", which I tried, didn't end up working. The gauges didn't respond at all to a constant 5.1 volts.

Please don't hesitate to tell me I'm an idiot and that you've personally replaced the original STABILIZER with a modern REGULATOR and gotten it to work on a car that used this stabilizer.

That is another good explantion of the stabilizer or regulator. If you looked at the old type on a scope. You would see a kind of saw tooth wave showing the signal you describe. The only reason a newer regulator might not work is if that version is not rated for high enough current to work for the gauges.

In the 240 cluster the early cars used a mechanical stabilizer as well. The replacement kits used to have a electronic regulator instead.

I would imagine the older gauges may require a lager regulator for higher current load. Other than that it should work. I have only used the TO220 7810 regulator for a 240 which worked fine. So I admit I haven't used one on the older cluster.

Well, my gas gauge doesn’t seem to be 100% accurate but both gauges are working now

Fuel was reading nearly empty and 6 gallons brought it back to full. I never had a problem with that before. Maybe I should just bend the arm on the sender and call it good?

AndrewNance said:

Well, my gas gauge doesn?t seem to be 100% accurate but both gauges are working now

Fuel was reading nearly empty and 6 gallons brought it back to full. I never had a problem with that before. Maybe I should just bend the arm on the sender and call it good?

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I'm guessing you've mounted the stabilizer back onto the cluster and that's gotten things working again. As far as your fuel gauge being inaccurate, did the 6 gallons truly fill it so that it's accurate when full? If so, does it suddenly change to showing empty when it gets to only about half full? If so, bending the arm isn't going to be a solution and I'm not sure if it would be under any circumstance. You may want to pull the sender out and inspect the very fine wires that wrap around the part of it where the "sensor" at the end of the arm travel across as the fuel level changes. Some of these wires may be broken or badly out of place, which would cause inaccurate readings.