Your light control module(LCM) may not be working. I replaced my air suspension system with regular shocks because of this problem. The LCM is a black box almost the size of a vhs tape found underneath the steering wheel.
In the Power Distribution Box in the engine compartment ( the P D BOX is " live " ) Relay # 303 ( one of the large relays ) is the air suspension relay
Hey Grady==You don't say what kind of car you have but most don't have relays on the compressor. Ihere is a cycling switch on the accumulator that when it is low will keep the compressor from engaging. GoodlukcJoe
GENUINE PARTS MFG: RELAY, F3LZ-2C013-B. DO YOU KNOW THAT YOU COULD REPLACE THE REAR AIR SUSPENSION WITH SPRINGS? NO MORE RELAYS, SWITCHES, AIR COMPRESSOR OR AIR LINES TO WORRY ABOUT. THANKS! J.T.
Besides fuses,there are relays that activate this compresorm most of them located under the hood; however, most of the compresors have a pressure control switch, if you have a small loss of refrigerant, eventually it is going to loose pressure an your compressor will not start to prevent compressor damage. Evacuate the system and refill with the correct amont of refrigerant.
The two types of relays commonly used to start a hermetic compressor are the current relay and the potential relay. The current relay activates based on the compressor's starting current, while the potential relay relies on voltage changes to determine when to switch the compressor on and off. Both types help ensure that the compressor starts efficiently and operates within safe parameters.
In the relay box next to all the other relays.
Two types of relays commonly used to start a single-phase compressor motor are the current relay and the potential relay. A current relay operates based on the current flowing through the motor, providing a boost to start it by engaging the start winding until the motor reaches a certain speed. In contrast, a potential relay uses the voltage across the start winding to activate and disconnect the start winding once the motor is up to speed. Both relays ensure efficient motor operation while protecting against potential damage.
2. The 4 by 100 relay and the 4 by 400 relay.
Check under the air filter housing for the PCM (power control module) if you could open it you would see about 5 relays on a circuit board one of the relays is for ac compressor. In general change the PCM.
I was looking at the power distribution box diagram for your 1998 Ford Expedition and it shows ( 6 ) relays but none of them are labelled for the air suspension In the P D BOX : fuse # 4 is a 15 amp mini fuse for the air suspension service switch and fuse # 15 is a 50 amp maxi fuse for the AIR SUSPENSION SOLID STATE COMPRESSOR RELAY ------------------------------------------------------------------------------------------------------- Just adding to my answer : I did a Google search and found that the solid state air compressor relay is mounted on a bracket near the passenger side headlight
Have you checked the relays?
Assuming you have checked the bulbs, check the brake light switch.