Weak suction - Broan-NuTone CV353 Central Vacuum

You sound pretty savvy in your troubleshooting. Take a look at this video. You may have a split in one of your three suction hoses. I tried to find a video for a DC24 but to no avail. These two models are pretty close and this video should help you out.

Vacuum leak. Check all the hoses and connections for leak. Fix them and you will have nice strong suction again.

if you've changed filters and checked for blockages it may need a new suction fan ,,you can download the diagram off the link below
http://www.ereplacementparts.com/black-and-decker-phv1800-dustbuster-parts-c-4167_8887_8897.html

is there a blockage in the inlet pipe ???

Is the tank filled completely with dirt? When was the filter last replaced or cleaned?

Check the motor and clean it properly. A very dirt motor will cause no suction or weak suction.
Be sure the motor is running on proper speed, a weak motor will cause a weak suction.
Thanks for asking.

If you are sure the is no leaks on suction line, please check and clean the filter. The common problem on weak suction vacuum cleaner are leaks and filter clog up.

Regards

Hello,
It sounds as though there is something stuck in the hose or outlet from the motor to the hose.

clean the filter abovethe dust cup... and any other filters

Either you have clogged filters, or the motor is weak, you could check the carbon brushes, otherwise replace the motor.