ProStar electrical issues

Hi, I am very frustrated with what’s going on in my 2019 ProStar LT and hoping to find some help. Last month, I replaced a bad leveling valve and A/C compressor. After these replacements, I started getting a high voltage warning. The battery voltage gauge cycles between 13V and 18V every few minutes whenever the engine is running. When it jumps up above 15V, everything on my dash goes haywire. The HVAC fan stops running, the radio turns off, ABS and Traction Control lights come on, the Cruise shuts off and the headlights get really bright. I have had the alternator replaced and the wiring and fuses checked. Penske keeps sending me back out on the road, telling me it’s fixed, but it is not fixed. Does anyone have any ideas so I might point the mechanic in the right direction?
Thanks so much.

 

Thank you I will try this!​

 

This seems to have worked. I disconnected the wire and have had no voltage issues since. Thank you so much!