Electrical Issues after HU swap

[Jdm.]

Hey guys, I just upgraded my headunit and now all my electrics seem to be playing up,
- my speedo jumps up when ignition is in
- central locking (factory) and aftermarket alarm aren't working

I've tried unplugging the battery and resetting the alarm but still nothing..

My car is a 02 DC5R

[mocchi]

who swapped the HU?
mustve cut wrong wire

[Jdm.]

My friend, we just swapped it from another aftermarket HU, so all the wires were the same, just had to re solder

[mocchi]

your speedo goes full tilt untill you remove ignition or just like a quick sweep

[Jdm.]

Quick sweep, happens sometimes not all

[mocchi]

i would try trace the vss wire from ecu to cluster and see if its shorting anywhere

[SQXPRT]

bad earth in engine bay - most common cause of faults with electrical in cars which are otherwise ok.