Booster fanot turning off - Fantech DB10 Pressure Switch Kit w/ Delay

When the brake booster light and brake light come on after replacing the batteries in a 2017 Isuzu NPR Diesel, it could indicate a problem with the brake system or a malfunctioning brake booster.
Here are some steps you can take to troubleshoot the issue:

1. Check the brake fluid level: Low brake fluid level can cause the brake booster light and brake light to come on. Open the hood and check the brake fluid level in the reservoir. If the level is low, top it up with the recommended brake fluid and check if the lights go off.
2. Check the brake system: Inspect the brake lines, brake pads, and brake rotors for any damage or wear. If the brake pads are worn out, replace them immediately.
3. Check the brake booster: The brake booster is responsible for increasing the force applied to the brake pedal. Check the brake booster for any damage or wear. If the brake booster is malfunctioning, it will need to be replaced.
4. Reset the brake booster light: If the brake booster light and brake light stay on even after checking the brake fluid level and inspecting the brake system, it may be necessary to reset the brake booster light. To reset the brake booster light, turn the ignition switch to the "on" position without starting the engine. Pump the brake pedal 3 times, then turn the ignition switch off. Start the engine and check if the lights go off.

If none of these steps work, it is recommended to take the vehicle to a certified mechanic or the nearest Isuzu dealership for a professional diagnosis and repair.

try this

1. Unlock the booster from the front of the dash.

1. Use a flat bladed tool (4) in order to pry the locking tab (5) on the booster out of the locking notch (3) on the mounting flange. Do this while turning the booster counterclockwise with a wrench (1) on the J 22805-01.

Notice: Do not attempt to remove the booster until pushrod is disconnected from the brake pedal.

its my pleasure to answer your question how to replace the brake booster :
1 With the engine off, step on the brake pedal several times to relieve the brake booster of vacuum.
2 Press the brake pedal down and start the engine. Verify that the brake pedal sinks slightly. Turn off engine.
3 Remove the vacuum hose from the brake booster.
4 Remove the brake lines from the master cylinder. Remove the master cylinder from the brake booster. Plug the fittings to prevent brake fluid seepage.
5 Disconnect the brake pedal from the push rod.
6 Have an assistant hold the brake booster from inside the engine compartment. Remove the nuts that hold the brake booster to the firewall. These nuts are usually located under the dash on the interior of the firewall.
7 Remove the brake booster.
8 Install the new brake booster to the firewall. Tighten the mounting nuts.
9 Connect the push rod to the brake pedal.
10 Connect the vacuum hose to the brake booster.
11 Attach the master cylinder to the new brake booster and reconnect the brake lines.
.12 Bleed the brakes at the master cylinder.

The following steps will help you to replace a Toyota Camry brake booster :
1 With the engine off, step on the brake pedal several times to relieve the brake booster of vacuum.
2 Press the brake pedal down and start the engine. Verify that the brake pedal sinks slightly. Turn off engine.
3 Remove the vacuum hose from the brake booster.
4 Remove the brake lines from the master cylinder. Remove the master cylinder from the brake booster. Plug the fittings to prevent brake fluid seepage.
5 Disconnect the brake pedal from the push rod.
6 Have an assistant hold the brake booster from inside the engine compartment. Remove the nuts that hold the brake booster to the firewall. These nuts are usually located under the dash on the interior of the firewall.
7 Remove the brake booster.
8 Install the new brake booster to the firewall. Tighten the mounting nuts.
9 Connect the push rod to the brake pedal.
10 Connect the vacuum hose to the brake booster.
11 Attach the master cylinder to the new brake booster and reconnect the brake lines.
.12 Bleed the brakes at the master cylinder.

12 specific steps will help you :
1 With the engine off, step on the brake pedal several times to relieve the brake booster of vacuum.
2 Press the brake pedal down and start the engine. Verify that the brake pedal sinks slightly. Turn off engine.
3 Remove the vacuum hose from the brake booster.
4 Remove the brake lines from the master cylinder. Remove the master cylinder from the brake booster. Plug the fittings to prevent brake fluid seepage.
5 Disconnect the brake pedal from the push rod.
6 Have an assistant hold the brake booster from inside the engine compartment. Remove the nuts that hold the brake booster to the firewall. These nuts are usually located under the dash on the interior of the firewall.
7 Remove the brake booster.
8 Install the new brake booster to the firewall. Tighten the mounting nuts.
9 Connect the push rod to the brake pedal.
10 Connect the vacuum hose to the vacuum brake booster.
11 Attach the master cylinder to the new brake booster and reconnect the brake lines.
.12 Bleed the brakes at the master cylinder.

only way i know to test a booster, is to turn engine off. use brakes several times till pedal is hard. then with brake applied,start engine. the brake pedal should then soften.if the pedal stays hard the booster is bad


Read more: http://wiki.answers.com/Q/What_are_symptoms_of_a_bad_power_brake_booster#ixzz2487DHV5I

the booster is the problem, or a hole or leak in vacuum line to booster check the check valve also ! from manifold. heres the symtoms of a bad brake booster. primary symtom is a hard pedal on application, to test booster. pump brakes several times with engine off. to deplete stored vacuum. turn on engine with pushing slightly on brake pedal. you should feel the pedal fade away abit and then become firm. but not hard. if you feel nothing at pedal when engine starts, brake booster is not working! check the vacuum lines first!!

Depends on how many amps the booster can supply. If the battery is completely dead then I'd imagine you need 150-200 amps to crank the engine ... probably way more than your booster has to offer.

hello there:
You will need to replace the brake booster to correct the problem in order to do this you will need to remove the push rod from you're brake arm separate the master cylinder from the booster and remove the four bolts on the booster and slide it out install in reverse hope this help you out sincerely D.Jones

the diaphragm in the brake booster is probably ruptured, replace booster