Dimmer switch lever does not hold in high beam

Low Beam System Operation
The headlamps may be turned on two different ways. First, when the end of the of the turn signal/headlamp switch lever is turned to the second detent position, the headlamps will illuminate. A ground signal is provided to the DRL control module. The module then provides a ground path to the coils of the HLP relay. Since the head relay is provided with battery voltage to both the contacts and the coil, the coil becomes energized and closes the contacts providing voltage to the DIM relay. With voltage and ground provided, the low beam lamps light. Second, with the switch in the OFF position, for automatic lamp control (ALC). During ALC the headlamps will be in one of the following modes of operation:
• Daytime running lamp (DRL) operation in daylight conditions, refer to DRL below for the operation of the circuit.
• Low beam headlamp operation in low light conditions. When the ambient light sensor senses a low light condition for approximately 15 seconds, it will cancel DRL operation and turn on the headlamps at 100 percent intensity. A path to ground is provided to the coil of the HLP relay. With a direct path to ground provided to the headlamps though the DRL control module, the headlamps will light at 100 percent intensity.
High Beam System Operation
The high-beam headlamp operation is controlled using the turn signal/headlamp switch lever on the steering column. In order to change headlamp operation from low-beam to high-beam, push the switch lever toward the instrument panel (until the detent is felt) and release. With the switch lever in the high beam position, ground is provided to the DRL control module through the turn signal/headlamp switch and splice pack 200 to G200. The DRL control module provides a ground to the coil of the dimmer relay. Since voltage is being applied to the dimmer relay coil, it becomes energized. Voltage is then applied through the closed contacts of the dimmer relay and the to the high beam lamps in the headlamps. Since ground is provided to the headlamps through the closed contacts of the energized DIM relay, the high beam lamps light. The high-beam indicator (blue) in the instrument cluster will light during high-beam headlamp operation. In order to change headlamp operation back to low-beam operation, pull the turn signal switch lever toward the driver (until the detent is felt) and release.Your best bet , take it to a qualified repair shop.

The service and repair manual with a diagram which will help you to locate and fix the problem on your own and you will get the manual from the given link http://toolsnyou.com

Here is how they are suppose to work .
Headlamps
The headlamps may be turned on two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the OFF position, for automatic lamp control (ALC). During ALC, the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. The LH HDLPand RH HDLP fuses, supply battery positive voltage from the underhood junction block to the left and right headlamps. The circuit continues through both low and high beam lamps, then back to the underhood junction block. The low beam and high beam circuits continue to the headlamp switch. The low beam and high beam circuits also provide the body control module (BCM) with both low and high beam inputs. The headlamp switch includes the dimmer switch and the flash-to-pass switch. When the headlamp switch is placed in the HEADLAMP position a path to ground is provided. Ground is provided at G201. Depending on the position of the high/low beam switch, either the low or high beam circuit will now have power and ground.
The LH HDLP fuse in the underhood junction block, supplies battery positive voltage to the automatic lamp control (ALC) headlamp relay coil circuit. The ALC relay switch circuit is connected to the low beam circuit at the headlamp switch. When the headlamp switch is placed in the OFF position, the BCM will automatically turn on the low beams in low light conditions. The BCM energizes the ALC relay, closing the switch contacts and grounding the low beam circuit. Ground is provided at G201. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed with the dimmer switch handle. The flash-to-pass feature is accomplished by pulling the dimmer switch handle toward the driver. The headlights may be switched to high beam with the opposite movement of the dimmer switch lever. When the headlamp dimmer switch handle is pulled toward the driver, the flash-to-pass switch closes grounding the high beam circuit. Ground is provided at G201. Both high beams will remain on until the driver releases the switch handle.
If the driver places the headlight switch in the HEADLAMP position , the headlights will remain on until turned off or the battery runs dead.

Finding a wiring diagram to use along with a DMM - digital multi-meter (voltmeter ) To test the electrical circuits for the headlamps B+ power & ground side of the circuit is the way to find a fix .
Watching a few basic electrical testing video's on youtube may help you .
Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts
How to Use Multimeter to Troubleshoot Common Problems
The Trainer 18 Electrical Testing Tips
Can take years to learn how to trouble shoot automotive electrical systems properly .

ok when push the lever forward the high beams don't stay on ? then that lever should be replaced cause that's ur dimmer switch to switch between high/low beam lights if the lever is bad can surge you headlight and blow the headlights, have you check headlight bulbs its rare but it has happened that both blow at the same time

The problem will be due to a malfunctioning headlight dimmer switch and a dimmer switch connector. Also check the high beam connector.

How do I get my High beams to turn off when the switch/lever is not working? (2012) Ford Explorer

Sounds like the headlight dimmer switch is defective. Remove the steering column covers and replace the switch.

Well it's hard to tell you anything as you did'nt call off the make year and model. the answer changes from one model year to another a 1935 model will be way different than a 1999. Most of the modern cheveys the combiantio switch is Bad 70's - 80's the dimmer switch is bad. the old ones have lots of problems with the floor switchs and the headlight switches but floor switches ended in the late 70's as they started putting relays and better everything in the more modern cars.

Check the headlight relay.

if this lever is part of the turn signal switch it might be faulty , also the auto dimming might be picking up glare from the bumper check the sensor and make sure it is clean.