16f873A PROBLEM WITH ADC

sbit LCD_RS at RB0_bit;
sbit LCD_EN at RB1_bit;
sbit LCD_D4 at RB2_bit;
sbit LCD_D5 at RB3_bit;
sbit LCD_D6 at RB4_bit;
sbit LCD_D7 at RB5_bit;

sbit LCD_RS_Direction at TRISB0_bit;
sbit LCD_EN_Direction at TRISB1_bit;
sbit LCD_D4_Direction at TRISB2_bit;
sbit LCD_D5_Direction at TRISB3_bit;
sbit LCD_D6_Direction at TRISB4_bit;
sbit LCD_D7_Direction at TRISB5_bit;

  //pic 16f873a fosc  20 M
char text[] = "lecture tension";

char chVAL[16];

float val=0;

  
 unsigned int   adcvalue,U;


void main(){

TRISB=0x00;
TRISA=0xFF;
PORTA=0x00;
 ADCON1.ADFM=1;
 ADCON1.ADCS2=0;
 ADCON1.PCFG0=0;
 ADCON1.PCFG1=0;
 ADCON1.PCFG2=0;
 ADCON1.PCFG3=0;

ADCON0=0b10000001                       ;     // fclok =f/32
  Lcd_Init();                  // Initialize LCD
  Lcd_Cmd(_LCD_CLEAR);         // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);    // Cursor off
  Lcd_Out(1,1,text);                             // Write text in first row
  Delay_ms(700);
  Lcd_Cmd(_LCD_CLEAR);         // Clear display
  Lcd_Out(1,1,"U1=");                                          // Write text in first row
Lcd_Out(2,1,"U2=");
 //
  
   do
 {

 //
     VAL=Adc_Read(0);
     floattostr(VAL*0.00489,chVAL);
     Lcd_Out(1,13,chVAL);
       Delay_ms(20);
     VAL=Adc_Read(1);
     floattostr(VAL*0.00489,chVAL);
     Lcd_Out(2,13,chVAL);
      Delay_ms(200);     //
 }   while(1);
}