expanding foam applicator gun

Hi,
I bought one of these:
http://www.toolstation.com/shop/Adhesives+Sealants/Applicator+Guns/Trade+Applicator+Gun/d180/sd3177/p75661
for occasional DIY use, after hearing them being recommended here.
I came to use it the other day and found that the some barely trickled out. I looked at the can of foam and it said "use by November 2011", so I thought that the foam had "gone off" or whatever foam does after it has reached its use by date. (what does happen to it?)
I bought a new can of foam but before fitting it I thought I would run some cleaner through the gun to make sure it was clear. Nothing came out the other end.
I'm now wondering if the gun is at fault rather than the foam?
Is there any DIY repair that can be made to the gun or is it just a matter of throwing it away and buying a new one?
I can't remember when I last used it. Perhaps the fact is that they are designed for regular use by tradesmen rather than occasional use by DIYers?
I think the price of the gun has doubled since I bought mine. I half wonder whether for occasional use I would be better going back to the handheld cans but expect to write off a can after each use. I suppose that would be fine except for very small jobs, where it would be a waste of a can.
What does the group think/do?
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Fred wrote:

http://www.toolstation.com/shop/Adhesives+Sealants/Applicator+Guns/Trade+Applicator+Gun/d180/sd3177/p75661
Strip it down and inspect and clean everything.
Sometimes bits of foam harden inside the gubbins and blocks it up. Unfortunately, foam cleaner does not remove set foam.
--
Tim Watts

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On 12/01/2012 21:22, Fred wrote:

http://www.toolstation.com/shop/Adhesives+Sealants/Applicator+Guns/Trade+Applicator+Gun/d180/sd3177/p75661
Sharp knife across the nose of it usually unblocks it.
Failing that, they are possible to take apart.

Been using the same gun for years now - quite often go months between uses.
--
Cheers,

John.

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wrote:

I was thinking of switching back to hand-held before I knew I could fix the gun. It's not something I use very frequently around the home but I think the guns are better where you are doing a project over a couple of days; I don't think a hand held can would last that long.
I bought new foam and used it all, so I put the expired can back on and it worked ok. I guess the problem had been that the can was cold and the gun was partially blocked.
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