Raspberry pi 4 booting but red led is not working

Disconnect all GPIO connections and bring the Pi up from a cold boot?

What light indications to you get when you boot?

Can you login into the Pi?

Can you measure the voltage between the 5V GPIO (pin 2) and Ground pin 39?

Hi Actually  i have cold booted as you said and the raspberry is on and i am able to login but still i am not able to get red led(pwr led). cold boot is noting but powering off the pi from the terminal and restarting it.

I dont have multimeter presently but i have measured the pin2 and pin 39 using a led  and it was glowing.

I am little confused why it is happening.can i you my pi now or something is damaged.

Cold boot is starting the Pi from a power off state. No power applied, the device is connected to the power supply and the supply is plugged into the wall.

The voltage measurement across the two GPIO pins was to determine what the Pi 5V power supply is reading. I'm wondering if the Pi 5VDC supply is above 4.5 https://elinux.org/R-Pi_Troubleshooting#Red_power_LED_does_not_light.2C_nothing_on_display   to cause the light to come on. An LED across the pins may light with just a little voltage. It is not an indication of the supply.

Do you have another external power supply you can try?

yes i have connected the pi to power supply and the pi is working  and  i am able to login but still i am unable to  get the red led on.

The green led is working fine.then what is the problem.

I have used type c usb adapter 5v 1 amp and i tried two to three different power supplies but still the issue is same.

You are at the end of the tether I can offer for help.

I'm not optimistic that you didn't impact the Pi power supply with the motor hookup. I have made similar errors in a physical hookup, that has rendered GPIO pin unservicable. The Pi boots and runs, I just have to remember some GPIO ports just don't work. It is no longer a project Pi but a demo I hand out in classrooms.

I'm thinking the Pi power supply onboard is not regulating the voltage needed to turn on the LED. A meter to measure the voltage could rule that issue out.

The Red LED indicates power. If it is blinking or off, your voltage from your supply is insufficient. You need a 5V 3A supply for the Pi4 - anything less is asking for instability and problems. Also, low quality cables cause voltage drops - so I'm not surprised you have this issue supplying the unit with just 1A (just a third of what is needed).

- Gough

Great catch L-G noting a 5VDC @ 1amp power supply is under rated to power a Pi4B. I didn't see the trees for the forest. TSG indicated it was working. I took that to mean working with the appropriate power.

It seems my approach to help desk is still not up to snuff. I suffered this same affliction when I worked computer help desk. I trusted and believed the user when they called. The cynical help desk person sitting next to me, got great enjoyment out of seeing me being lead to my own demise bu users. His moto, Never trust what a user tells you. NEVER! I found his approach rather harsh. He wasn't popular with the user community but rarely was he lead astray troubleshooting a user problem.

SG, as L-G is pointed out, their are specific power supply requirements for a Pi4B. The specification are higher than early models of Pi's. A 1amp power supply is from the days of the first Pi model. You need to confirm the power supply specifications to see if that may be causing your issue.