Headlight module question

[mikenfl]

I'm converting the headlight motor control system on my '85 'Vette, with it's 3 external relays and 3 internal switches per motor to use a module from an '87 and up Firebird. I got the module from a salvage yard and after hooking everything up there was no ground output from the module. The + output was switching but no -. I figured the module had to be bad so I went back to the Pick-N-Pull and exchanged it for another one. Got it home and.....same thing It seems unlikely to get 2 in a row with the same problem but everything else seems to be good. The input ground is good at the harness pin. I can't think of what I'm missing. Does anyone have a manual with a diagnostic procedure for the module? Is it possible to check/test one with a DVOM?
Thanks in advance for any help.

[hotrod_chevyz]

you picked the worst headlight system in the world to try and be fixing man.Mines an 82.At first it was that they messed up in the rain.Then after i bought all new relays and replaced one headlight motor just cause it was noisy now they dont work at all.The relays was 17 bucks apiece.The headlight motor was $50.00 used,and i tested it making sure it worked on the car i got it from ,using the new relays i bought to test it with.I know i should try and replace the headlight switch or make sure its plugged in,but after all that i just screwed them up manually,pulled the relays and forgot about it.Good luck

[mikenfl]

Anybody else?