I doubt it would hurt plastics or the insulation
on the wiring. I'm in water
treatment and we feed straigft acid though plactic tube and pumps without problems. Phosphoric acid is a fairly weak acid, but it has to be flushed/neutrazied after using or it will eat though the metal (keep it away from alumimum). I would be more worried about he acid getting into the wiring under the insulation so would say it's a must to remove the wires while using it for cleaning
. I used to build custom bicycles and used the auto paint
type prep acid a lot for cleaning
the tubes before painting. I would recommend something like this over the Home Depot type of phosphoric acid type cleaners.