Hopefully someone is not still having a problem with this one but if any one else has the the same issue check the assembly to ensure that it is properly assembled. I had this same issue in the early 80's and after trying 2 more new adapters from PLL which had the same issue I took one apart and...
Try checking your right front glad hand cover it should have a small hole in it or the type with a vent valve. If your cover has the vent valve ensure that it is clean and functioning as intended. Only the right front requires this vent function.
If you are looking for the ones that look as the Military light due, check www.truck-lite.com. The current one the military get work on 10 to 30 volts. The first ones were either 12 or 24 volts so check which one you find.
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