HP — 4 beeps continuous
Four beeps from an HP desktop or laptop is the power-failure code. Something in the power chain — PSU, motherboard regulator, or laptop battery — is unable to provide stable voltage. Here is how to find which.
What the beep code means
Four beeps from an HP signals a power failure — the BIOS detected that one or more of the system voltage rails (typically the 12V, 5V or 3.3V supply) is unstable, missing, or out of spec. The BIOS halts before something downstream gets damaged.
The cause is almost always one of three things:
- The power supply is failing under load.
- A voltage regulator on the motherboard has failed.
- (Laptops only) A swollen battery is physically shorting power pins, or its protection circuit has died.
Laptop diagnosis
Step 1 — check for battery swell
Press both palms gently against the bottom of the laptop. The bottom panel should be flat. If it bows outward (even slightly), the battery has swollen. This is a fire risk and needs immediate replacement.
Other signs:
- Trackpad has stopped clicking properly (the swollen battery is pressing it from below).
- Bottom panel screws no longer thread cleanly because the case has flexed.
- Keyboard has developed a slight upward bow.
Step 2 — try AC-only operation
If your laptop has a removable battery (older HP ProBook, EliteBook 8x0 G5 and earlier), pop the battery out and try to boot on AC power alone. If it boots, the battery is the problem — replace it.
For internal batteries (most modern HP), this requires opening the laptop and disconnecting the battery cable from the motherboard. If you are not comfortable doing that, take it to a repair shop and ask them specifically to test it without the battery connected.
Step 3 — try a different charger
A failing charger can cause unstable rails that look like a power-failure code. If you have access to another HP charger of the right wattage, try it. Watch for the wattage rating — using a 65W charger on a laptop that needs 90W can produce intermittent boot failures.
Desktop diagnosis
Step 1 — reseat the PSU cables
The 24-pin and 8-pin (or 4+4) connectors going from the PSU to the motherboard must both be fully seated. A partial connection on the 8-pin CPU power line can produce the 4-beep code under load.
Power off, unplug, press both connectors firmly until you hear a click. Power back up.
Step 2 — disconnect non-essential hardware
Unplug everything except: motherboard, CPU + cooler, one stick of RAM, integrated graphics output (no discrete GPU), and the 24-pin and 8-pin power. No drives, no extra fans, no expansion cards, no USB peripherals.
If it boots in this minimal config, add components back one at a time until it fails again — that identifies the part overloading the PSU.
Step 3 — try a different PSU
If you have a spare PSU (or a friend with one), swap it in. If the 4-beep code stops, the original PSU was failing. PSUs typically last 5-10 years; cheaper units fail at the lower end of that range.
Step 4 — visual inspection of the motherboard
With the PSU disconnected, look at the capacitors near the CPU socket. They should be flat on top. Any that are bulged, leaking brown crust, or split open are failed and the motherboard needs replacement.
When to give up and replace
If you have ruled out the battery (laptop), the PSU and the cabling (desktop), you are almost certainly looking at a motherboard-level VRM failure. On a desktop this is a £80-150 board replacement; on a laptop it is usually £200-400 plus labour and rarely worth it on a machine older than four years.