heating problems

hi everyone, just wondering if you could help me with some heating issues
im having problems sustaining the required heat for the hotend and the heatbed. say for example i were to turn on the hotend first it would climb to around 215 C then drop to 185 ( set tempt) taking a total of 86 seconds, then i if i turned on the heatbed, the heatbed would climb to about 45 C (60 C required) in about 24 seconds while the hotend drops in temp then the heatbed temp starts to drop. i have checked the voltage at the power source and its still about 12 v i even tried turning it up to 14 v but not change. before i had the heatbed working the hotend would reach the required temp and stay there no problem. note that i had to swap my heatbed wiring to D9 and change the pins.h settings to suit as for some reason it wasnt working in d8. i am using sprinter and pronterface the pins.h settings are as follows:
#if MOTHERBOARD == 33
#define MOTHERBOARD 3
#define RAMPS_V_1_3
#endif
#if MOTHERBOARD == 3
#define KNOWN_BOARD 1

//////////////////FIX THIS//////////////
#ifndef __AVR_ATmega1280__
#ifndef __AVR_ATmega2560__
#error Oops! Make sure you have 'Arduino Mega' selected from the 'Tools -> Boards' menu.
#endif
#endif

// uncomment one of the following lines for RAMPS v1.3 or v1.0, comment both for v1.2 or 1.1
// #define RAMPS_V_1_3
// #define RAMPS_V_1_0

#ifdef RAMPS_V_1_3

#define X_STEP_PIN 54
#define X_DIR_PIN 55
#define X_ENABLE_PIN 38
#define X_MIN_PIN 3
#define X_MAX_PIN -1 //2 //Max endstops default to disabled "-1", set to commented value to enable.

#define Y_STEP_PIN 60
#define Y_DIR_PIN 61
#define Y_ENABLE_PIN 56
#define Y_MIN_PIN 14
#define Y_MAX_PIN -1 //15

#define Z_STEP_PIN 46
#define Z_DIR_PIN 48
#define Z_ENABLE_PIN 62
#define Z_MIN_PIN 18
#define Z_MAX_PIN -1 //19

#define E_STEP_PIN 26
#define E_DIR_PIN 28
#define E_ENABLE_PIN 24

#define E_1_STEP_PIN 36
#define E_1_DIR_PIN 34
#define E_1_ENABLE_PIN 30

#define SDPOWER -1
#define SDSS 53
#define LED_PIN 13
#define FAN_PIN 9
#define PS_ON_PIN 12
#define KILL_PIN -1
#define ALARM_PIN -1

#define HEATER_0_PIN 10
#define HEATER_1_PIN 8
#define TEMP_0_PIN 13 // ANALOG NUMBERING
#define TEMP_1_PIN 14 // ANALOG NUMBERING
#define TEMP_2_PIN 15 // ANALOG NUMBERING

could anyone please help me as i am stuck not knowing what to do and really want to start printing

Measure the 12v while both are on. If it drops significantly you need a larger power supply. Also make sure the wires from PS to board and from board to hotend and bed are large enough to handle the current.

i originally though it was a power supply problem but measuring the voltage it doesnt drop much or below 12v i even had it up to 14.49v with both heatbed and hotend on as for the wires, the hotend uses a cartridge so its the wires it comes with and the heat bed uses 16 awg wire

can anyone help me please?

oh and i have switched hotends but didnt change anything

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oo thank you

Try changing the MOSFET that controls your heatbed. This has made a difference on my i3, not perfect as yet but I suspect my power supply is the problem as I am not getting 12V at the heatbed terminals.

Regards
Nige