Mixer shower problem with hot water

[blue2red]

Hi I'm experiencing problems with a mixer shower.
When the taps are run both hot and cold water exit the taps.
When the plunger is pulled up to divert the water to the shower head only cold comes out.
The hot water is certainly at a lower pressure than the cold - would this have anything to do with cold only from the shower head?
I'm looking for advice on how to cure this problem. Any suggestions would be welcome.
Many thanks.

 

[JCplumb]

put the shower head at the same level as the taps. If hot and cold come out of it then you have a pressure problem.
Is the shower a new installation? If so I'm guessing you don't have enough head.

 

[blue2red]

Thanks very much for your feedback.
I need to look at this and assume pressure is a problem I assume an under bath pump should solve the problem?
Hot water is from a storage cylinder so yes not enough height.
Could I re-route a direct feed to the shower from hot water riser from the cylinder at a height above the shower to get the head I need.
I'm thinking the the best fix here though is a pump?

 

[Megaflo-Experts]

I would expect the hot and cold to be the same pressure, assuming the cold water is supplied from the water cistern, and not the mains.
Yes, a pump would probably solve the problem.