Dell Latitude 3510 Overheating & Fan Control Issue – Need Help

[Ven]

Dell Latitude 3510 (Intel Core i7-10510U) CPU Overheating

Issue Description:

1. CPU Overheating to 100°C
   • When I start the laptop from a cold state, it takes about a minute to reach temps around 80-90-100°C, and CPU thermal throttling triggers.
   • When the CPU fan is running at full speed (by disconnecting PWM and TACH cables), CPU temperature stays around 50-60°C.
   • However, when the fan is connected normally to the motherboard, it does not kick in at high temperatures.
   • I also noticed a few times that the fan kicked in for a very short time, but it does not stay on consistently.
   • Thermal paste has been replaced with fresh paste, and the heatsink is firmly attached.
2. Fan PWM & TACH Signal Issues
   • PWM signal stays at a solid 3V (does not switch to a square wave to start the fan turning).
   • TACH signal remains at 0V, obviously fan is not turning.
   • Compared with another working Dell laptop, the PWM signal should be a square wave when the fan spins, but it remains solid 3V on my faulty laptop.
3. Core Thermal Throttling Triggering
   • Watching CPU package temperature with HWiNFO, I can see the thermal throttling happening when temps reach high levels.
4. Temporary Fix: Lowering Maximum Processor State to 90%
   • When I change CPU Maximum Processor State to 90% (default is 100%) through Windows Power Options > Advanced Settings, everything returns to normal:
     • No overheating
     • No throttling
     • VRMs do not get extremely hot
5. BIOS & EC Firmware Updated
   • Updated BIOS to the latest version, which included an Embedded Controller (EC) firmware update as well.
   • No noticeable changes in fan behavior or temperature management after the update.

What I Have Tried So Far:

✅ Replaced thermal paste (correctly applied, heatsink is secured).
✅ Checked fan operation (spins at 5V).
✅ Updated BIOS to the latest version (including EC firmware update).
✅ Checked VRM 1V coils – extremely hot at high CPU temps.
✅ Confirmed BIOS power and cooling settings.
✅ From Dell Power Options app, I changed system power setting to COOL, no help.

I am attaching images of the screen showing CPU temp.

No visible component damage, everything looks normal.

Rather than the fan not turning on (because there is no PWM signal), I believe the main issue is the CPU's sudden and erratic temperature spikes.

Any advice or suggestions would be greatly appreciated! Thank you.

[mcplslg123]

Are the VRM coils marked R15? If yes replace them with R22 marking coils and you will see cpu running alot cooler.
Absurd but true.

Even if the coils seems ok,just replace them .

[Ven]

Are the VRM coils marked R15? If yes replace them with R22 marking coils and you will see cpu running alot cooler.
Absurd but true.

Even if the coils seems ok,just replace them .

Yes they are R15. I will replace them as soon as I can.

[Ven]

nobody has idea?

[rogfanther]

Can you try with another fan ? If yours is not generating the tach signal, maybe it is defective.

[Ven]

Can you try with another fan ? If yours is not generating the tach signal, maybe it is defective.

I have tried another fan and it is still same. When I go to Pre-boot diagnostics, I can manually test fan, which passes test. On the other hand, while computer goes through other tests, like memory, CPU etc, CPU gets very warm and fan doesn't spin. Even Dell website says fan will spin at full speed during these test as they stress the system. I have ordered EC Chip and lets see what will happen afterwards.