heating only works when I run the [cold] hot water

[nigelad]

Well I mentioned on another thread that our Gem combi boiler had packed up. The hot water stopped working but the CH was ok. Then BG engineer came and replaced a divertor valve, which hasn't fixed the problem. So he then diagnosed it as a faulty heat exchanger, which can't be replaced.
Then we found out that the CH didn't work any more.
However, last night I discovered that if I run the hot water, the water is cold, but the heating comes on.
Does this tally with the BG diagnosis?
And is it safe to run the water to get some warmth?
Thanks in advance...

 

[DP]

Looks to me a case of 'try this- if it does not work, change that'. Shame, there are some good engineers within the company but thin on the ground. Get them to prove that the heat exchanger is defective.

 

[nigelad]

Cheers DP.
So is it safe to run the hot water as a way of getting the rads to come on?