Power rail failure 3 amber and 5 white LED blink code

Hi

The fastest decision tree is: hard reset → BIOS recovery → test with known-good AC adapter → if unchanged, replace the system board.

Which you have done methinks.

ELSE

Make sure the Dell charger is known-good and that the DC-in connector is not loose or damaged, because adapter or input problems can mimic a board fault.

If the motherboard has been replaced twice and each one is getting 3,5 error, then I would look into replacing the I/O daughterboard. It'd be pretty odd for it to cause the particular issue, but it would be the next part that makes sense for this platform. Had this been a no post code of 2,8 or 2,7, then I would believe the LCD and EDP cable were an issue. A lot of the time, those 2 post codes are going to need a motherboard, LCD, and EDP. However, the 3,5 does isolate this to a different power rail. 

@DELL-Daniel V​ 

I hope this email finds you well.

Acknowledge receipt of your email. Thank you for the prompt response; it is much appreciated. Please be advised that we do not have a spare or known-good daughterboard in stock to use for testing purposes. As we are unable to swap this specific component to rule it out, we will just lodge a separate new RMA request in the Dell TechDirect portal for the I/O daughterboard.

We will perform another round of troubleshooting and diagnostics on the device once we receive the new motherboard and I/O daughterboard; we will update accordingly.

Best regards,

Ike A.

@DELL-Daniel V​ 

Subject: Update: Dell Latitude 3450 - Persistent Power Rail Failure (3-Amber, 5-White)

Good morning. I hope this email finds you well.

I am providing an update regarding the ongoing technical issues with the Dell Latitude 3450. We have received and installed the third replacement motherboard, but the fault persists.

To isolate the root cause, I performed a systematic test on this new board by disconnecting all non-essential components (daughterboard, SSD, Wi-Fi card, and LCD cable).

Diagnosis Summary:

• Initial Test (No RAM): Using a known-good power adapter with all components removed, the system produced a 2-amber, 3-white LED code. This confirms the board is functioning enough to detect the absence of memory.

• Secondary Test (RAM Installed): Upon reinstalling the RAM, the error code immediately reverts to 3-amber, 5-white (Power Rail Failure).

Despite this being the third motherboard replacement, the Power Rail Failure persists as soon as the memory is introduced to the system.

Current Constraint:

Please be advised that we currently do not have a spare or known-good DDR5 RAM stick in stock for cross-testing. Consequently, we are unable to swap this specific component to definitively rule it out as the source of the short or rail failure.

I will continue to investigate the remaining peripheral components, but given that this is the third board, the RAM is now a primary suspect. Please advise if you can provide or suggest if there are further diagnostic steps you would like us to take.

<To protect you, your private information was removed from public view. All private data was saved to your private Case. DELL-Admin>

Thank you for your attention to this matter.

Best regards,

Ike Alumani
IT Technician | Global Internet Limited

Hi

I thought that you needed DDR5, hence the thought about trying RAM from the problematic Slim Plus, however I now have second thoughts.

""Please be advised that we currently do not have a spare or known-good DDR5 RAM stick in stock for cross-testing.""

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The Dell Pro Slim Plus QBS1250 uses DDR5 UDIMM desktop memory, with four memory slots and support for up to 128 GB total. It supports module sizes of 8 GB, 16 GB, and 32 GB per slot, and speeds up to 5600 MT/s depending on configuration.

The Dell Latitude 3450 uses DDR3L 204-pin SO-DIMM memory modules, typically 1600 MHz (PC3L-12800), non-ECC, with support for up to 16 GB total across 2 slots.

@DELL-Daniel V​ 

Good day and I hope this message finds you well.

I am providing an update on the Dell Latitude 3450. We have confirmed that the RAM is the component triggering the 3-amber, 5-white LED blink code.

While this specific code typically indicates a power-rail failure, my testing has isolated the RAM as the actual culprit:

• Test 1: I installed a known-working RAM stick from another Latitude 3450 into the unit. The computer powered on successfully, reached the display, and prompted for initial configuration.
• Test 2 (Reverse Test): I installed the suspected faulty RAM into a known-working unit. The issue persisted, and the working unit immediately began triggering the 3-amber, 5-white blink code.

It is interesting that a faulty RAM module is mimicking a power-rail error code; I’m unsure if Dell Support has encountered this specific crossover before, but the results are conclusive.

I will wait for the replacement RAM from the RMA that we requested. Once it arrives, I will perform the final testing.

Best regards,

Ike Alumani

 <To protect you, your private information was removed from public view. All private data was saved to your private Case. DELL-Admin>

@anne_droid​ 

Good day and I hope this message finds you well.

I am providing an update on the Dell Latitude 3450. We have confirmed that the RAM is the component triggering the 3-amber, 5-white LED blink code.

While this specific code typically indicates a power-rail failure, my testing has isolated the RAM as the actual culprit:

• Test 1: I installed a known-working RAM stick from another Latitude 3450 into the unit. The computer powered on successfully, reached the display, and prompted for initial configuration.

• Test 2 (Reverse Test): I installed the suspected faulty RAM into a known-working unit. The issue persisted, and the working unit immediately began triggering the 3-amber, 5-white blink code.

It is interesting that a faulty RAM module is mimicking a power-rail error code; I’m unsure if Dell Support has encountered this specific crossover before, but the results are conclusive.

I will wait for the replacement RAM from the RMA that we requested. Once it arrives, I will perform the final testing.

Best regards,

Ike Alumani

@ikealumani​ certainly an odd one that the memory was causing the 3,5 code, but glad to hear its fixed!