Glow plug problem/ harness reading 4.7 volts

Newbie here. I read some other glow plug threads but couldn't get anything conclusive. I've got a 2005 jetta showing a a code for each glow plug. Testing them they have consistent resistance (.7oms i think). The harness reads 4.7 volts consistent across each boot thing.

When I bought it it had a replacement 109 relay on the floor (which I think came from a 2001 jetta that the guy was working on) but I switched it out and it ran the same. Oh and the fuse above the battery is good. Does that mean its the harness? I've read that cleaning them can make a difference. But could that really be the cause if they are all reading the same voltage? The harness and wiring to it looks okay. Is there any way of telling by look if it needs to be replaced? Any other suggestions?

Oh and since about the time I took the harness off it seems that I have a drain on my battery. Could that be related?

Any help appreciated! Thanks

Some TDIs have 5v glow plugs. I don’t know more than that but it might help.

Also sort of relevant, some multimeters can’t read the voltage properly.

http://forums.tdiclub.com/showthread.php?t=474002

Sent from my iPhone using Tapatalk

Yup, your TDI will have 5V or 7V glowplugs, depending on if certain recall campaigns were done.

And, the voltage itself is pulsed.. which some meters read as a lower voltage still.

Are you getting a Check Engine light with glow plug codes?