ADC 10-bit false results

I'm using atmega32 µc with the internal 10-bit ADC. I connected my potentiometer to the ADC 1 and I'm using 5 V Voltage Reference.

using the following code, I did the ADC-config

void ADC_init(void)
{

    //Turn on the ADC
    ADCSRA |= 1<<ADEN;   // Turn On ADC (Enable ADC)

    //ADMUX  |= 1<<ADLAR ;  // Config shifting to the left (10-bit), otherwise it is right adjusted

    ADMUX  |= 1<<REFS0 ;  // Config VRef (external Vref in this case)
    ADMUX  |= 1<<MUX1 ;  // ADC-Channel 1

//  ADCSRA |= 1<<ADIE;   // Enable ADC Interrupt
    ADCSRA |= 3<<ADPS0;  // Assign ADC-prescaler 128

    ADCSRA |= 1<<ADSC;   //start the the measure conversion
}

Then in Main function I am calling the following function each 1000ms and send the data to the USART interface

void ADC_measure(void)
{
    _delay_ms(50);

    // if the ADC right adjusted
    theLow = ADCL;  // ADC Value Low
    _delay_ms(50);


    ADC_TenBit = ADCH<<8 | theLow  ;  // because of lift adjustment of ADC

    _delay_ms(50);

    sprintf( ADCBuffer, "The ADCValue is : %d \n", ADC_TenBit );

    _delay_ms(50);

    usart_pstr(ADCBuffer);

    _delay_ms(50);
    //start the the measure conversion
    ADCSRA |= 1<<ADSC;
}

The problem is : when I open the terminal , I see only the ADC Value = 255 or 248
increasing or decreasing the potentiometer value doesn't change the ADC value.

what can I do now?