Your univolt is obviously dead, or at least dying. If you don't want to replace it with the appropriate and expensive converter, go to Walmart and buy the biggest automatic automotive battery charger they sell, and install it. It should keep you going, not cost an arm and a leg, and can be of some use when you do get around to installing a new proper converter.
On the other hand, the univolt is a very simple devise, like a fixed voltage power supply, and would be easy to repair at any decent electronics shop if you got it out and took it in.
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