Two Problems Gas Gauge and Battery

The gas guage on my 2003 Rendezvous spun around and now points down and doesn't register the fuel. Anyone know how to fix this?

Also the battery goes dead after the vehicle sits for a day without driving. The battery was changed in July and I just had the car in the shop a month ago and the battery is good and the charging system is working good. The dealer told me that the Radio was drawing too much amperage and said the radio was bad. they charged me $100 too just trace the electrical to see where the problem was and to pull the fuse so the radio wouldn't work. They wanted $300 for a new radio. I bought a new one on ebay for $31.00 and put it in but the battery went dead again yesterday. Any suggestions?

We have put $2000 in to repairs on this vehicle in the past 9 months and we are getting to the point that this vehicle is a lemon.

Welcome to the club. The gas gauge could be that the rehostatic sensor in the tank is dead. You can buy just the sensor off of the web and from GM so if someone tells you that they have to change the fuel pump as well ($300) tell them where to go.

As for the power drain. I have no clue. Have you tried pulling the radio fuse to see if that fixes the problem?

It sounds like you have parasitic drain which can be caused by any electrical problem and could be complex to troubleshoot and resolve. But you should have the retained accessory power - RAP feature as do most if not all late model Buick models.

Retained accessory power. Power windows and radio remain operational after ignition is switched off for 10 minutes or until a door is opened. Doesn't make sense for the radio to draw that much as stated or the cause if the RAP is working properly. The RAP relay is controlled by the BCM - body control module.