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Checking Voltage Drop When Upgrading T25 Interior Lights to LEDs

Posted: 15 Oct 2026, 10:59
by cedricuk
When upgrading interior lighting on a T25, how do you check whether the existing wiring and connections are suitable for LED replacements?
 Would you measure the voltage at the light fitting under load, inspect the earth connections first, or check for voltage drop along the wiring?
 I'm interested in the practical checks that help identify poor connections or inconsistent voltage before replacing parts unnecessarily.

Re: Checking Voltage Drop When Upgrading T25 Interior Lights to LEDs

Posted: 15 Oct 2026, 15:05
by mioba
If they were suitable for incandescent they sure will be suitable for led.
if it works it works.

Clean the connections at the fitting and the earth.

If you need to check the v drop, Measure at fuse box and then measure at the fitting.

Poor connections - it will work or it wont with flickering.


do continuity tests or make up a simple test bulb.

Re: Checking Voltage Drop When Upgrading T25 Interior Lights to LEDs

Posted: 17 Oct 2026, 08:51
by cedricuk
Thanks, that makes sense. Measuring at the fuse box and then at the light fitting gives a useful comparison if voltage drop is suspected. Cleaning the connections and checking the earth first also sounds like a sensible starting point before replacing anything. Appreciate the practical advice!