[GEAR] [QUESTION] Fender Blues Jr. Volume Fading in and out

Yes, the Radiator heat can harm the amp. The amp is biased quite hot on the output tubes, so it produces quite some heat itself, you should better cool it instead of heating it up. If you have no clue of electronics or amps i'd recommend to bring it to a specialist.

I have a Les Paul, and have had the same problem because the selector switch was losing its contact. Have you been able to test with another guitar? Is the issue all the time, or after some playing, or only on occasion? Can you test by temporarily moving the amp, letting it cool, and playing through it?

Heat is bad for electronics. Tubes may look fine, but if they've been overheated, there could be problems.

Take it to a tech. If you swap tubes, you'll likely want to get it biased as well.

Well knowing nothing about tube amps despite having one here’s what I found after a google search.

I’d try checking the volume and master volume pots, maybe some connection is bad there. Found someone saying that after quick search.

Check the actual solder joint for the tubes.

Seems like the general consensus is tubes going bad though.

Turn the master volume/volume down independently, and see what effect that has.

To be clear I know nothing about tube amps. 😂