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740 Cruise Control Dosent work

Vacuum hose for CC under dash either fell off, or is rotten.Is a common failure. Could be other things, but I'd check that 1st.
 
The vacum hose runs from the pump, mounted on the left hand side of the engine bay, to an air switch on the top of the brake pedal.
If you have a manual gearbox there is a second switch on the top of the clutch pedal.
It could be that a joint has dislodged.
Here is a diagram:

C__Info_vv132023_img_part_18_map_gr.jpg


If your car has LH2.4, the cruise control can be checked using the OBD box in the engine bay:Cruise Control Onboard Diagnostic Codes link
 
Four modes of failure I encoutered.

1. torn vacuum diaphragm

2. broken throttle spool let cable fall off

3. vacuum T too-far on air pump blocking hole.

4. bad bulb-failure relay (you won't have brake lights either most likely)
 
Have you been under the dash wiring/working on anyhting lately? If so, I'd check that vac hose underdash by clutch peda, & IIRCC, there is a roundish thing above & behind the M/C on the firewall, under the hood, that has a CC vac hose that likes to fall off.l
 
Usually it is simply that the cruise vacuum switch is incorrectly adjusted. If you hook your foot behind the brake pedal and pull it toward you while setting the cruise control and it suddenly works, adjust the vacuum switch.
 
2manyturbos said:
Usually it is simply that the cruise vacuum switch is incorrectly adjusted. If you hook your foot behind the brake pedal and pull it toward you while setting the cruise control and it suddenly works, adjust the vacuum switch.
Click to expand...

^^this! if your car has a manual gbox you also need to check the vac switch under the clutchpedal.
 
both are checked for prober adjusting but if they work thats another question

i have been told that i can messure Resistens in them like when they pedal is pushed or released
 
gmtgmt said:
both are checked for prober adjusting but if they work thats another question

i have been told that i can messure Resistens in them like when they pedal is pushed or released
Click to expand...

Pull the switches out of the car and check that way. Not only does the electrical contact need to close but they also need to hold a vacuum.
 
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