Waited this morning until the temps got up to 50F and the slides started working again. I check the battery voltages as I passed the panel in the hallway just after retracting the small bedroom slide (it's a clothes closet) and they read 13.7 Volt house, and 12.8 Volt chassis. I do have a Trik-L-Start installed.
jdealcpa: Front slide moved fine after it warmed up, although it seemed a little slow. RV jacks were down, RV nice and level, no bad sounds while it retracted. I haven't thought about starting the engine first, I'll try that tomorrow morning bright and cold.
dougrainer: Such a great test. Why didn't I think of that? I did not check the jacks when the slides were not working as I just didn't think of it. I will if they don't work tomorrow.
I'm now settled in at a nearby RV park for 4 days, which should be 28F again tomorrow morning. I'll test using all the suggestions.
Mr. Wizard - I'm hard of hearing, but normally I think I can hear the pump OK but only in the LR (though it may just be incidental noises associated with the slide rubbers). In the BR, can't hear it at all. Even when the slide is moving. Don't have anyone to listen for me, so I try to not use hearing as a guide. I just watch carefully.