well I've found the issue. I replaced a stuffed t/stat with a new cheap t/stat from ebay which was also rooted.
after taking it back out and heating both t/stats I found the old one opened at 82* but didn't close properly which explains the previous low temp alerts and the fact that when decending Mt Lofty the temp reported below 1/4 on the gauge on cold mornings.
The new 91* t/stat barely opened at 100* which explains the higher temps I had with it.
I purchased a new expensive 82* t/stat like my old one and now the temp is sitting just over half even going up Mt Lofty with the A/C on.
Hopefully now that it closes properly there will be no more low temp codes.