I think you may be mis-reading the diagram in the manual. At the moment I only have a copy of the 2013 manual but it indicates that Fuse 13 (in the upper right corner of the diagram) is for Cabin Heater Pump and Valve. Relay 13, in the center of the diagram, is listed a couple of pages later in the Mini-Fuse table as Empty. And Relay 3 is for the Powertrain. Fuse 3 is unused.I'm having similar problems with my recently purchased 2014. My first step in troubleshooting it was to check the fuses and relays. The owner's manual said there should be a relay in spot #13 of the Engine Compartment Fuse Block for the Cabin Heater Pump and Valve. However, mine is completely missing the relay in spot #13, and since I'm new to this Volt, I'm not sure what was done to it before I got it. I've tried to get the relay from two dealerships in my area, but they've both told me that Volts aren't supposed to have a relay there, even though the owner's manual says otherwise. On a related note, the owner's manual said the relay in spot #3 was unused, but when I removed it I got a check engine light talking about the emissions system (went away after a couple of charge cycles with it back in place).
Can anyone willing to help check if you actually have a relay in spot #13 of the engine fuse block? If so, would you mind telling me the part number and/or specs listed on the relay? The parts people at both those dealerships both said they couldn't look up what relay should be there without reading the numbers off an existing one.