01 F350 power locks work weak

I have 2001 F-350 powerstroke crew cab that the power locks barely operate when engine is not running. Have to press 5-6 times to get to fully operate. Like they are not getting suffecient voltage? They work fine when engine is running. I did install aftermarket remote entry several years ago and worked just fine until last 3-4 months. I tried greasing components I could access. Any ideas? Thanks.

I would check the voltage at the solenoid and check the drop when you activate the switch, you may just need to clean the ground side of the connector or worst replace the solenoid.

First check the voltage at the battery It should be about 12.4V with the engine off and about 14.4V with the engine running.

You can clean the battery terminals and the ground wire between engine and body, which may go to the firewall.