Tough Cruise control problem
04-27-2013, 11:13 PM
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Tough Cruise control problem
tough one to crack on "97 F150 Supercab, 4.2, 5 spd... Took to transmission shop for clutch, clutch master and slave cylinders, and hydraulic line between master and slave. Got truck back, and cruise doesn't work! Checked VSS on rear of manual trans, wires are connected and speedometer works fine. Only other connection is reverse indicator and it is connected. Other details:
1. Brake pressure sensor checks good (replaced it anyway), continuity (0 ohms) when no brake, and no continuity when brake depressed). Power to sensor is 12V thru both recall harness or direct wired.
2. Checked servo, and all gears inside turned freely and cable to throttle was not stuck or broken.
3. Replaced servo with one from salvage yard, did not fix the problem (no proof that one was good or bad). Checked cable and it was not frozen or broken either.
3. Tested speed sensor input to servo at 10 pin connector (pin 3) with AC voltage tester and it varied appropriately with speed, about 4 volts ac at 40 mph.
4. Power to pin 7 is 12V at servo connector, just as it should be.
5. All 3 brake lights are working and none stay on when brake released.
6. Horn works fine, unless connector is removed at servo. checked both fuses under hood and inside cab, all are good.
7. Removing connector at brake switch, confirmed 12V across wire connector, and switch terminals have full continuity (0 ohms) when depressed, and no continuity when not depressed.
8. Engine would not start unless clutch was depressed, so clutch switch should be good? Couldn't reasonably access the pins to test that switch but confirmed the connection was intact and not corroded, and all wires in tact.
9. Confirmed 12V at servo connector pin 5 when steering wheel switch depressed to "ON", and 0v when switched "off".
10. Confirmed continuity (0 ohms) between pin 5 (control) and pin 6 (control ground) only when set/resume/coast control buttons depressed. No continuity if buttons not depressed
11. Confirmed continuity (0 ohms) between servo connector pin 10 and chasis ground.
12. this year model does not have a light on the instrument cluster, and thus, does not do a self check of components (at least not that I know of)
Here are some things I don't understand...
1. Pin 4 at servo connector (brake pedal position) shows only 1.2V when brake depressed, instead of 12v. (Checked with 2 separate meters) Also, pin 9 (Brake pressure sensor) shows the same 1.2V at the servo connection when brake not depressed (0V when depressed) Another post says this should be full 12V.
2. Another post says pin 5 should show some varying voltages when set/accel/coast are depressed and key on. I dont see any on the meter.
The cruise worked on the way to the trans shop. I can't believe it just magically quit unrelated to trans work, but I can't see anything other than VSS that would affect cruise, and it tests good. We have worked on this for 2 weeks and can't figure it out... Help!
1. Brake pressure sensor checks good (replaced it anyway), continuity (0 ohms) when no brake, and no continuity when brake depressed). Power to sensor is 12V thru both recall harness or direct wired.
2. Checked servo, and all gears inside turned freely and cable to throttle was not stuck or broken.
3. Replaced servo with one from salvage yard, did not fix the problem (no proof that one was good or bad). Checked cable and it was not frozen or broken either.
3. Tested speed sensor input to servo at 10 pin connector (pin 3) with AC voltage tester and it varied appropriately with speed, about 4 volts ac at 40 mph.
4. Power to pin 7 is 12V at servo connector, just as it should be.
5. All 3 brake lights are working and none stay on when brake released.
6. Horn works fine, unless connector is removed at servo. checked both fuses under hood and inside cab, all are good.
7. Removing connector at brake switch, confirmed 12V across wire connector, and switch terminals have full continuity (0 ohms) when depressed, and no continuity when not depressed.
8. Engine would not start unless clutch was depressed, so clutch switch should be good? Couldn't reasonably access the pins to test that switch but confirmed the connection was intact and not corroded, and all wires in tact.
9. Confirmed 12V at servo connector pin 5 when steering wheel switch depressed to "ON", and 0v when switched "off".
10. Confirmed continuity (0 ohms) between pin 5 (control) and pin 6 (control ground) only when set/resume/coast control buttons depressed. No continuity if buttons not depressed
11. Confirmed continuity (0 ohms) between servo connector pin 10 and chasis ground.
12. this year model does not have a light on the instrument cluster, and thus, does not do a self check of components (at least not that I know of)
Here are some things I don't understand...
1. Pin 4 at servo connector (brake pedal position) shows only 1.2V when brake depressed, instead of 12v. (Checked with 2 separate meters) Also, pin 9 (Brake pressure sensor) shows the same 1.2V at the servo connection when brake not depressed (0V when depressed) Another post says this should be full 12V.
2. Another post says pin 5 should show some varying voltages when set/accel/coast are depressed and key on. I dont see any on the meter.
The cruise worked on the way to the trans shop. I can't believe it just magically quit unrelated to trans work, but I can't see anything other than VSS that would affect cruise, and it tests good. We have worked on this for 2 weeks and can't figure it out... Help!
04-28-2013, 07:52 PM
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Solved...
2 lessons: 1) it's always the small things, and 2) NEVER ASSUME anything!
As mentioned, the cruise was not working after returning from trans shop. They rechecked their work and said they did nothing to affect cruise control other than VSS speed sensor and it was working fine. Ergo, not their problem...
My ASSUMPTION that since the truck would not start without depressing the clutch, and therefore, the clutch switch must be working, was only partially right. THIS SWITCH HAS TWO (2) SETS OF CONTACTS, ONE FOR THE CRUISE AND ONE FOR THE ENGINE START. The contacts are on opposite ends of the clutch switch. You CAN have one set functioning and not the other!! How? read on...
The problem turned out to be that clutch switch was not installed back correctly on the clutch pedal rod, and you had to look closely to see it! The shop did not carefully reinstall the clutch switch as it was before they started, and it was rotated about 30 degrees, which prevented it from seating all the way and allowing the internal contacts for the cruise circuit to mate. This resulted in the switch contacts for the cruise being "open" in the resting position (they must be closed to allow the permissive for the cruise to operate). The switch MUST be mounted back on the shaft carefully, so that it fits into an indentation on the clutch master cylinder housing. Only then will the internal contacts match and create the circuit. If done wrong, the cruise will NOT work, but the starter prevention will function normally.. This is a rather complicated little switch.
This could have been caught early if you could reach the switch pins to test them with a meter, while the switch is mounted on the clutch rod. Its impossible! You can barely reach the wiring harness connector to unplug it. As another poster said, you have to practice yoga just to get under the dash to see all this. I hope this helps someone, it was a miserable 2 weeks for my son and I checking, rechecking, and rechecking all the components and overlooking this small issue....
As mentioned, the cruise was not working after returning from trans shop. They rechecked their work and said they did nothing to affect cruise control other than VSS speed sensor and it was working fine. Ergo, not their problem...
My ASSUMPTION that since the truck would not start without depressing the clutch, and therefore, the clutch switch must be working, was only partially right. THIS SWITCH HAS TWO (2) SETS OF CONTACTS, ONE FOR THE CRUISE AND ONE FOR THE ENGINE START. The contacts are on opposite ends of the clutch switch. You CAN have one set functioning and not the other!! How? read on...
The problem turned out to be that clutch switch was not installed back correctly on the clutch pedal rod, and you had to look closely to see it! The shop did not carefully reinstall the clutch switch as it was before they started, and it was rotated about 30 degrees, which prevented it from seating all the way and allowing the internal contacts for the cruise circuit to mate. This resulted in the switch contacts for the cruise being "open" in the resting position (they must be closed to allow the permissive for the cruise to operate). The switch MUST be mounted back on the shaft carefully, so that it fits into an indentation on the clutch master cylinder housing. Only then will the internal contacts match and create the circuit. If done wrong, the cruise will NOT work, but the starter prevention will function normally.. This is a rather complicated little switch.
This could have been caught early if you could reach the switch pins to test them with a meter, while the switch is mounted on the clutch rod. Its impossible! You can barely reach the wiring harness connector to unplug it. As another poster said, you have to practice yoga just to get under the dash to see all this. I hope this helps someone, it was a miserable 2 weeks for my son and I checking, rechecking, and rechecking all the components and overlooking this small issue....
