windshield wipers wont turn on

[81ratrodc10]

hi all i have searched this and a few other forums and didnt find the answer i was looking for so here goes. bear with me its gonna be a bit long winded. i have an 87 m1028 cucv that i converted to gas prior to the conversion i was having problems with my wipers not working. it turned out to be the connections to the motor. once we respliced in some new butt connectors i never had a problem with it again. fast forward to last month when i finally completed the swap. i have no wipers again. i found a wiring diagram and kind of a test walk through but it didnt give me a definitive answer. it did help me with the way the switch is supposed to function tho. so heres were im at. with the truck off the 3 wire plug at the bottom of the wiper motor has no power as i would suspect its supposed to. when you turn the ignition on to run all three wires light up the test light very brightly. i know the switch on the column is the ground activation for the motor to function. when i turn the switch to low one wire loses power like it supposed to. the main power wire keeps the test light nice and bright but the other wire lights it up pretty dimly. if you switch it to high you get the same effect with the opposite wire. why would once the switch is engaged the power going to the plug seem to drop? do i have a bad ground? if so were is the ground for the switch located? how do i test it any further? please help its killing me not to be able to use my wipers.