I found my notes on how to bypass the automatic propane shutoff solenoid.
Propane detector supplies the following to open solenoid
12-volts to open
2-volts to keep open
107 ma (milliamps) to hold open
I took the pintle out of mine so it would not shut off. I was having problems with my propane detector (replaced) and the new one did not have the ability to shut off the system as did the OEM propane detector. As I understand, the national rv manuf. assoc. no longer requires this on newer RVs. So, Attwood does not make them anymore. They are available but not by OEM manuf. (which I believe is Attwood). So, got my new Attwood sans cut off circuits and removed sliding pintle by propane regulator and all works and I did this probably 2 years ago and no complaints from me on the change. Also I believe my propane detector is also carbon monoxide also, so I now have two carbon monoxide detectors (as I still have original and believe it to be working).
Our propane detector has not been working properly for quite some time, however we kept it operational with a SPDT switch for the periods we were on the road so the fridge could run on propane (we don't use the gas stove burners). Lately the propane detector would work for only a few hours before shutting the propane off (and beeping...).
Looking at Barry's solution, i came up with the following circuit (I didn't feel confident trying to modify the propane valve as others have done). I post this for those who still have the same issue.
I had a spare DSN2596 (https://www.ebay.com/itm/DSN2596-DC-3-50V-to-1-5-35V-DC-Voltage-Step-Down-Transformer-Module-for-Arduino-/141769706032) (buck converter) that I had paid a $1 for years ago, a SPDT switch and a momentary on switch. I bought an electrical box and cover at Home Depot and came up with the following (the momentary switch is to apply 12 volts for a second or two to open the solenoid, the 2 volts to keep it open):
I just looked at mine. I have two black wires to that shut-off valve. I had thought about cutting the wires, but it sounds like that would close the valve. It looks like I could close the main valve, then remove the electric shut-off valve and replace it with a piece of straight pipe. Is that what others have done?
I was not aware that propane detectors age out and should be replaced every 5 years. While at MOT last month my detector was replaced. I had the solenoid on the tank removed.
This is common, as newer coaches do not come with the solenoid. Not that they are a bad idea, but no longer available.
As I see it your circuit will not work-you can't use DC on a AC transformer. You can use a 2 resistor voltage divider, one resistor will drop 10 volts and the other will supply the 2.5 volts. 100 ohms and a 20 ohms should do it, the valves on/off coil would be the "20 ohm" resistor.
Good catch! The drawing tool i used didn't seem to have icons for the DC converter (DSN2596). The circuit works fine and would work with a voltage divider as well. I had the buck converter on hand but not the appropriate resistors.