hi anyone have an issue with erratic volume on the stereo...the issue i have is that if your turn the knob, sometimes it goes up or down, even if you are turning it in the same direction it will become erratic and go up and then down, or vice versa...it is intermittment and doesn't seem to have much rhym or reason...also the volume controls on the steering wheel work just fine and don't exhibit the problem...my mechanic just fixed my cigar and cigarette lighters and now i have this problem all of sudden...so i am assuming it is related...could it be a grounding problem, or did he fry something?

 

Newer car stereos (the Jag's included) don't use resistive potentiometers for volume anymore, instead they use an optical rotary encoder that sends signals to the microprocessor in the stereo. This consists of a toothed wheel and a pair of LED's and photo diodes that send a pulse train as the wheel blocks and unblocks the light from passing between the LED and the diode.

If one of these LED/photo diode pairs becomes faulty or a large spec of gunk covers the diode's surface, then the pulse train that is sent doesn't make sense to the microprocessor and it will get confused as to what you are really doing with the knob.

The only solution is to either replace the head unit, or, if you're handy, to disassemble and hope that you can either clean the crud that's blocking the diode or resolder the bad connection... etc.

I had this same issue with the stereo in my 02 Explorer - upon disassembly, I found a broken intermittent solder joint on one pin of the encoder device. A simple hit with a soldering iron resolved the issue.

 

thanks for the tip...i just bought a new head unit on ebay...hopefully that will do the trick...one thing i did notice though...when the problem happens, if i turn off the car for about 10 seconds and turn it back on the problem vanishes....so i don't think anything is dirty, i think something is funky though and leaving the car off for 10 seconds and turning it back on seems to fix the problem...i wonder what the car does in those 10 seconds that is fixing the problem...hmmm...

 

Sounds more like an intermittent solder joint OR one of the LED's (or some other component in the encoder loop) overheats and fails, then comes back after the short cool down?

 

many thanks for the info...the one thing i noticed is that if i try the same thing by shutting the radio off and waiting 10 seconds it doesn't fix the problem...it is only after i turn the car off for 10 seconds...wouldn't turning the car off and shutting off the radio do the same? is there some other place a thermal shutdown could be occruring besides the Radio Head Unit? just trying to pin point as best i can so i know what replacement parts to order...thanks quad man

 

hey i got another problem...the issue is with the factory cellphone...the audio from the phone to the car stereo is very very low now...sometimes it is normal but for the most part now it is very low...i am assuming all of this comes back to the head unit? when the cellphone volume is low i have the same erratic volume control problem...any ideas?

 

The radio head unit is still powered when the key is on. Turning the head unit off only disables the output, but most of the electronics are still powered (the phone still works, for instance).

Re the phone volume: The last phone volume setting set by you will be stored for the next use... if control is erratic, is it storing a very low setting? As you are trying to turn it up, but it's erratic, it stores whatever value it was at right when it switches back to stereo mode - if this (erratically) was a low setting, that's what gets stored.

Hopefully, your new head unit will resolve all of this... and then, if you want to, you can disassemble and see what's going on with the defective rotary encoder circuitry.