quick oddball glow plug question

1z tdi in 79 rabbit. i have 12v at the pins on the tdi glowplug harness however the gps don't heat up. i'm not using a gp relay, just a manual push switch. i did ground the plugs in the block and also to the body of the car when i had them out of the block so its not that. is it that one of the wires on the gp harness isn't suppose to be 12v? there is two as seen in the pic below. anyone?

i suppose all gps could be bad although i am getting decent resistance readings. so doubtful

Did you check to verify you're getting 12V off the supply line? Could be a faulty switch. Try tracing the 12V supply back to where it originates from to make sure you're not grounding out between the switch & the plugs. You can verify that the plugs are good by running a lead directly off the battery.

yea yea yea i'm getting 12v at the gp pins on the harness

Gp needs to be grounded at the metal threaded part, with 12v on the terminal. You stated that you grounded them, are you sure you got a good connection? Normal ohm reading a few ohms. Burned out is very high reading.

Usually, the GPs will show about .8 ohms, and sometimes as high as 1. As mentioned above, they have to be grounded at their bodies in order to glow.

Make sure your pushbutton switch is rated for a boat-load of amperage!

-Rich