Bosch PS42 Stalls At Times

[Bardiferously]

Some prior mention back in 2016, but no real answer to this. My brushless impact driver, Bosch PS42, even with fully charged battery installed, will occasionally stop while the trigger is pulled. Sometimes under a load, sometimes not. And a pull or three later, or going in reverse, and it's working again as if it never stalled, even running until the battry is empty.

I've heard suggestions that contacts are dirty, the trigger might be damaged, a battery might have issues; but I've not seen a clear response of a fix that works. Any help, fellow Garage Keepers?

Help!!!

 

[RTM]

If it was mine, I'd decipher your clues more before I opened it up. Consistently try the same thing to see if it consistently fixes it. Then try fix B, then C.

Places to fail are
Battery connection
Switch (f-r) connection
Trigger connection
Trigger
Whatever replaced the brush to motor connector
Bad spot on the armature


Of course there are more, but eliminate as many as possible that don't do anything first, then chase the few that are left once it's open.

Back in the brushed motor days, ran into a drill motor with a bad (dirty) spot on the armature. Rotate it a bit, off it went. Relatively easy fix. Modern electronics, not so much.

 

[MoonRise]

Using some google-fu:

- thermal protection shutdown, on the battery or the motor or electronics

- dirty contacts. On the battery, the drill, the trigger switch, the forward/reverse switch, etc

- other intermittent electrical connections, such as a cracked solder joint (harder to diagnose without some level of teardown)

Cut-and-paste right from google, so the formatting is meh here. I'm not going to fully pretty it up for you. Lol

"bosch ps42 intermittently stops working"

When your Bosch PS42 12V impact driver intermittently stops working, it is usually caused by a drained or failing battery, dirty battery contacts, or a tripped thermal protection circuit within the brushless motor controller.

Troubleshoot the most common culprits in this order:

1. Battery and Contacts (Most Common)Check the Battery Level: The PS42 features a fuel gauge on the tool itself. If it drops by a bar or two, the internal protection circuit can cause the brushless motor to stall under load. Swap in a fresh, fully-charged 12V Max battery.Inspect the Battery Receiver: Corrosion, debris, or bent terminal pins inside the tool's base can disrupt power delivery.Clean the Connections: Wipe the battery blades and the tool's internal contacts with a clean microfiber cloth. If debris is deep inside, use an aerosol contact cleaner to wash it out.

2. Overheating & Protection ModeLet it Cool: Pushing the impact driver to its limit (driving heavy/long screws) can heat up the motor and controller. The tool’s internal electronics will temporarily shut down to prevent permanent damage. Let the tool and battery rest in a cool place for 10–15 minutes before using it again.

3. Switch and ElectronicsTrigger and Speed Board Issues: Intermittent power or the tool dying in the middle of a job can sometimes stem from worn micro-switches or cracked solder joints in the trigger or speed selector, often brought on by repetitive vibrations.Testing: If the LED lights work but the motor will not spin—even after cleaning—the switch or control board may need to be replaced.For a visual guide on inspecting battery contacts and the internal receiver nodes, this video breaks down how to replace the battery receiver if the pins have lost their tension:11mHow to repair a Bosch GBH36VF-LI see drill that keeps stopping.YouTube · Dean DohertyIf you'd like, let me knowo the LED lights stay on when the tool stops, or do they flicker/go dark?Does the tool work again immediately after swapping to a different battery?Does it only stop when you are driving heavy-duty fasteners, or does it happen under no load as well?I can help you narrow down if it's an easy cleaning fix or if you need to look into replacement parts.4mBosch 12V Brushless Impact Driver - PS42-02YouTube·Tools In ActionBosch drill not working : r/BoschProPowerTools - RedditMar 15, 2025 — Was using my brushless drill for some work today and it suddenly stopped working. The led works and it spins like once per 30 times I try to start it. Tried cha...Reddit·r/BoschProPowerToolsBosch Drill not working when the trigger is pulled slowly - RedditNov 14, 2025 — I will try cleaning the switch, thanks. * FnarFnarAway. • 8mo ago. It's not normal behaviour. Watch Dean Doherty on YouTube. He fixes power tools and does a boa...Reddit·r/Tools11mHow to repair a Bosch GBH36VF-LI see drill that keeps stopping.YouTube·Dean DohertyRepairing a Bosch Impact wrench with a faulty speed selector button ...May 23, 2024 — Gun is working but cannot change speeds. Luckily @boschprouk supply the electronic speed selector board seperatly from the motor controler. Which makes this a q...Facebook·Deandohertygreaser7:07Why Impact Wrench Triggers Fail (Repair Guide and Reverse ...YouTube·Hugatry's HackVlogBosch 18V Drill Won't Work? Expert Troubleshooting Guide - JustAnswerAug 27, 2025 — Open the drill housing using Torx screws. Look for the two brushes on either side of the motor. If they are very short, chipped, or not spring-loaded, they need...JustAnswerIssues with PS22 12V hex driver - Bosch - Power Tool Forum{"passageText":"Brushless Tool Stalling: Bosch PS22 12V hex drivers and similar brushless tools can experience intermittent stopping, often when the battery fue...forum.toolsinaction.comWhy is my Bosch drill working intermittently?{"passageText":"Drill Intermittent Functionality: Intermittent operation in a Bosch drill, where it only works after reinserting the battery, can often be resol...diy.stackexchange.comWhy Does a High-Current E-Bike Controller Cut Out at Full Throttle?Aug 1, 2025 — Yes. If the controller or motor gets too hot, built-in thermal protection can shut down or limit power until temperatures drop. This prevents permanent damage.