Airlock in heat exchanger ?

Hello there,
I have a conventional boiler and an indirect hot water cylinder with a heat exchanger. Rads are heating up fine - water runs from the hot water tap but it is cold - from reading around I think I either have an airlock in the coil inside the tank or a faulty motorised valve. Anyway of differentiating between the two ?
If it is an airlock should I just drain the whole system and refill ? Are the any other ways ? Where is the motorised valve for determining whether I get HW+CH or just HW ?
Any help appreciated - my little 'un wants a bath !
Regards
Chris
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If it's an airlock you could tell by opening the nut to the cylinder (from the boiler) slowly and carefully the air should come out with considerable force after only one or two turns. You probably need to fit an automatic air vent on the top of this pipe to the cylinder or a "finger vent"(if there isn't one already fitted) which you use to fill it manually. If no air lock then you'll have to ignore the above and find the motorized valves. They are usually somewhere near the pump switch the black lever from auto to manual and see if it makes a difference. It's a good idea to fit an immersion heater for these eventuallities.
Jon

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