Wrong colors plotting to Canon iPDF710

Here's a doozy. I think it's CAD file related but can't pinpoint it. In our job, one of my CAD guys published files from two different ACAD models (one plumbing and one hvac piping) to PDF. I have our ctb setup to plot our background (color as light/grey scale. For some reason it plotted the background as a slight purpleish (similar to color 171). BUT when he published the two together, the plumbing drawings came out fine, and only the HVAC piping ones plotted this way. Which lead me to believe it was the CAD file.

However, now none of us can duplicate it and it's always plotting the purple no matter what. I've checked the layer colors, the VP colors, we've tried publishing, DWG to PDF, straight to plotter, etc. It all comes out the same. I don't think plotter ink is the issue as it should all be plotting black and white and our main piping and border is plotting fine. The PDF's we create look fine as well.

Anyone have suggestions? We have a Canon iPF710.

TIA

Not sure what ipdf710 is but some colour printers use colour to make black like wise grey maybe a cartridge problem. Play with the windows printer settings photo etc.

yes ipf710 is a color plotter. But the rest of black lines show up fine. I've emailed Canon support so we'll see how that goes.

After talking to Canon support, we resolved this and thought I'd share. Simple fix. Went in to Adobe>Print>Advanced and checked "Print as image". I asked why it would have worked before and not now and they suggested a simple windows or adobe update may have reset this. All is well now