Heat surges on and off...any ideas?

I have a 98 Jimmy slt, with computer controlled climate control. This morning i went to start it up and had no power so i jumped it. Since then the heat surges from hot to cold. I tried turning the dial to the coldest setting and it still surges from hot to cold, and at what would appear to be regular intervals. I'm stumped on this one... any ideas?
Also, I just had the thermostat replaced about a month ago, and recently (within the last couple days) i did notice that the thermostat needle sits just below the 200 mark instead of 2 notches below like normal. I dont think these two are related, but thought it might help.

Always check the coolant level in the overflow tank and rad.

If it acted up after a dead battery or jump it may need recalibrated.

A dead battery or jump can spike your AC/heat controller and throw it out of calibration.

To calibrate it with key off remove the RDO/BATT fuse for 30 seconds or more and the put fuse back in .
Turn key on and it should go threw the recalibrate mode and start working right.
If not you will need a AC/heater capable scanner to find the problem.
Good Luck
MT

Also better check out the reason the battery was dead.

thanks MT ill give it a shot. as far as the batt, its in need if replacing soon but im trying to avoid it. It was a really cold morning and it had been sitting for a few days.

You are welcome.
Let us know how it goes.
And get the battery fixed as soon as you can.
A weak battery can cause a lot of problems.
Good luck
MT

ok i tried removing the fuse for 30 secs and no luck. Do you think it could possibly be a vacuum system problem? I did notice while sitting in it today that i can hear a change in the flow of air when it goes from hot to cold. It doesn't move from defrost to panel or any other location though. also, if i have the fan off and have outside air selected should i get air flow into the cabin still?

Vacuum maybe.
It has vacuum and electric controls both.
But if it quit right after dead battery it points to electrical.
Have you checked all fuses and power supply?
Have you fixed the battery?
To check the auto controls you will need a auto matic ac/heater control capable scanner?

Have you switching from auto to manual mode and setting it to the highest tempt setting like full hot?

money is tight right now so i gotta put off the batt for a little while longer. ill have to check with the parts store to see what type of scanner they have. Yes it does it at any point from full cold to full hot. even on full cold it still spits out hot then cold.

Get the battery as soon as you can or it may cause a lot more damage.
Good LUCK
MT