1st post and ofc multiple problems to deal with
 

I have been trying to help my friend out in fixing his 2005 monte and I desperately need some guidance. This all started while trying to sort his overheating issue. We have found out it's not actually overheating but the lying gauge that we thought was the little motor issue with the cluster. Changed the cluster and it still did the supposed overheating but the new cluster speedo did not work. I was going out of town and he said he'd just swap out the cluster since he had seen how to do it and in the process pulled the keys out of the ignition, while the power was still hooked up, causing it to no longer start or even move. Replaced that with a used ignition switch out of a yard and after relearn fired right up no issue until i find out that now his wipers work when they please if at all. I don't think any work i've done has caused the new wiper problem, but, since i've had a hand in this i feel obligated to help.

Overheating: I have changed the thermostat, sensor on the housing, and tried a different cluster. The fans cycle when they're supposed to when checked with a thermometer versus the in the red dash reading. Before i had entered this he had the system flushed/filled, many hours of supposed diagnostic labor, and was told his problem was with his catalytic converter so he did that as well.
Wipers: When i tried them using the switch nothing happened no noise or movement from the motor or spray. The only thing i did in dash was cluster twice and swap out his ignition switch splicing together the 3 little wires in the side(tan,yellow,and black). Blinkers still work.
Any help in resolving either of these issues will be greatly appreciated

Now his cars battery has died in the driveway 5 days after the last time i even touched it and i also need to find and fix this problem as well

Have you considered the ECT sensor? I had some false readings on my '06 for a while until I realized that the connector was loose. After I made sure it was secured, I no longer had the problem.

If the ect is the one on top of the thermostat housing that was replaced along with the stat when i first entered this mess. I will double check that connection though

Update:Wipers always work when key is ON but once started may or may not work(mostly not)