Canon 5D & 580EX/580EXII Manual Setting Issue

I am having trouble using Manual setting on these flashes (580 EX and EXII) with my 5D when I am in Program or Aperature or Shutter Priority Mode on the camera itself.
I want to set the camera say to 1/160th of a sec in Shutter Priority, or to f/8 in Aperature Priority and then on the flash i change try to change it to Manual mode where should be able to change the setting from 1/1 down to say 1/4 or something less in order to add a little fill flash. When I do this though, on the camera it automatically changes to f/22 and the flash won't fire. I just want to have a little fill light. I think it does this too while in Manual mode on the camera but I forget right now as I am not at home with my camera to try it... I've checked the manuals for any kind of warnings but found nothing...
any ideas?

By the way the flashes work great when slaved to an ST-E2 on the top of my camera... but not when they're directly attached to the hotshoe.

When the camera is in Av or Tv mode, the camera meter is set to expose the ambient light. When you set the Tv to 1/160 and see the f22 flashing, that means the there will be severe underexposure at 1/160 and lens at max opening. Anyway, it's a bad idea to shoot with manual flash in Av or Tv mode as we don't have much control over the flash exposure.

You can set the flash to ETTL mode and use the FEC to weaken the fill flash, or if you like to use flash in manual mode, set the camera to M mode too, use the shutter speed to control ambient, dial the manual flash to match the aperture setting on the camera, lets say f5.6, before taking the shot, set the aperture to f8 or turn down the flash power a notch.

StephenJames wrote in post #5863259
I am having trouble using Manual setting on these flashes (580 EX and EXII) with my 5D when I am in Program or Aperature or Shutter Priority Mode on the camera itself.
I want to set the camera say to 1/160th of a sec in Shutter Priority, or to f/8 in Aperature Priority and then on the flash i change try to change it to Manual mode where should be able to change the setting from 1/1 down to say 1/4 or something less in order to add a little fill flash. When I do this though, on the camera it automatically changes to f/22 and the flash won't fire. I just want to have a little fill light. I think it does this too while in Manual mode on the camera but I forget right now as I am not at home with my camera to try it... I've checked the manuals for any kind of warnings but found nothing...
any ideas?

By the way the flashes work great when slaved to an ST-E2 on the top of my camera... but not when they're directly attached to the hotshoe.

When using the flash in manual mode, you should also be using the camera in manual mode, too, or, at least, that's how Canon feels about it. That is the reason your shutter speed, for example, gets set to the fastest one available on the camera when it's set to Av mode and the flash is in manual mode. If you want the camera to be in auto mode (Tv, Av or P), then the flash should be in auto mode (ETTL), too.

Thanks much for the replies, I'll have a check to see if I can use the Manual flash settings when I'm in Manual mode on the camera.. for some reason I think i tried that and it still gave the same flashing f/22...