Instructions on how to use the fender frontman 212r amplifier.

sounds like bad caps and maybe a failing output transistors. Use Deoxit contact cleaner too.

After ruling out guitar wiring or bad cables...
Try the 2nd input on the amp
also
Is it on both channels, or just one?

PRE OUT/PWR IN - (1) Effects Loop - Connect PRE OUT to an effects device input, then connect the effects device output to PWR IN. (2) Multiple Amps - Connect the primary unit's PRE OUT to the auxiliary unit's PWR IN. The primary unit is used to control all auxiliary units. (3) Recording or Reinforcement - Connect PRE OUT to sound equipment's input. Both jacks use a TS (Tip-Sleeve) standard type plug for connections. PRE OUT includes onboard tone shaping.

... do you, by any chance, have non humbucking pick ups on your guitar? Just curious...

The power amp input jack takes "line level" input BUT is monaural (single channel). The output of an ipod is Stereo. Hence you would have to "mix" the two channels before connecting to the Fender. Mixing does NOT mean just tying the two channels together. A minimu thing would be a passive resistive mixer consisting of a resistor from each of the IPOD channels to the common point going to the input of the Fender. Remember if you plug into the Fender power amp input you DISCONNECT the preamp and other circuits and would ONLY hear the IPOD input.

When i turn on my 212R it turns on in drive channel. if footswith is plugged in, then it turns on in the clean channel, but after switching in drive it is impossible to switch it back in clean channel. What could be wrong? Swith position doesnt change anything and it seems like switch is OK.

No, when you plug into the power amp in that disconnects the feed-through of the preamp.

You don't say if you are using a footswitch or not... If you are, the switch, cables and connectors are suspect.

If you are NOT using the controller, the switch contacts on the footswitch jack in the 212 are suspect as being intermittent contacts.

If the contact is not making, the OD switch on the unit will NOT work either.

These jacks, and their contacts are JUNK and often cause problems.

Open the unit and increse the tension of the contact springs.

Start with everything in the 12 o' clock position. Adjust one thing at a time until it sounds good to you.