It might be the converter, or it might not. It could just be a loose wire.
What you have to do it check the converter output right at the converter terminals. If you have good converter voltage there, then you have bad wiring from the converter to the battery.
I found out this from experience, and as I checked it out, I wiggled the negative wire on the converter terminal strip. All of a sudden the lights came on bright, and I had found my real problem. Changing out good converters usually results in tightening of the associated wiring, and presto, suddenly you have a several hundred dollar bill for no good reason.