Crusing---Not!!!
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Crusing---Not!!!
The cruise control in my 1991 f-350 idi hasnt worked since I purchased it. I can't find any diagrams or other information about the system. Does anyone out there have any information to share on cruise control for this truck?
Posting Guru
Joined: Oct 2005
Posts: 1,030
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From: Powell River B.C.
Same thing with my 93. All the electrics checked out good, problem was from lack of use the stepping motor in the actuator unit had siezed up. I removed the cover, which contains all the PFM electronic modules, lubed up the motor and gear train bits with WD-40, grabed the drive shaft with small vice grips and broke it free, once free and lubed up, my Cruise works great now. (it took me two years to get a round to it, and 20 minutes to fix.) HA HA!
Senior User
Joined: Jul 2006
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From: south jersey
i thought it would be easier to just post it. lol
Speed Control Systems
Description and operation
The speed control system is composed of on-off, set-acc, coast and resume (if equipped ) switches. The system contains vacuum hoses, servo (throttle actuator) assembly, speed sensor, amplifier, check valve assembly, and depending on model and year, a clutch switch, stop light switch and/or vacuum dump valve. 1983-86 models w/resume, also use a vacuum reserve tank. To operate speed control system, engine must be running and vehicle speed must exceed 30mph. When "on-off" switch is actuated, the system is ready to accept a set speed signal. When vehicle speed stabilizes (exceeds 30 mph), and the "on" switch is engaged, the operator may depress or release the "set-acc" button. This speed will be maintained until a new speed has been set, brake pedal has been depressed, or the system is turned off.
Basic Diagnosis and Troubleshooting
Inoperative:
1. Blow the horn. If found satisfactory, proceed to step 2. If not, check horn circuit (power)
2. Apply brake pedal and ensure brake lights work. If found satisfactory, proceed to stop 3. If not found satisfactory, check stop lamp circuit.
3. Check for physical connection of clutch and brake electrical switches at clutch and brake pedals.
4. Check operation of vacuum dump valve on end of vacuum hose at brake arm on brake pedal.
5. Check proper operation of actuator lever and throttle linkage.
6. Check for proper vacuum at actuator.
7. perform tests on control switches and circuits.
8. perform tests on actuator.
9. perform tests on sensor.
10. perform tests on amplifier.
Control switch test
Disconnect 6 way connector from control switch at the amplifier, then perform the following checks. (amplifier is usually located under the dash behind the radio or ash-tray)
<DIR>connect a voltmeter between light blue-black hash lead and ground, then depress the "ON" button and check for battery voltage.
Turn ignition "off", then connect an ohmmeter between light blue-black hash lead and ground. Rotate the steering wheel throughout it’s full range while making the following checks:
a. depress "off" button and check for a reading of 0-1 ohm.
b. Depress "set" button and check for a reading of 646-714 ohms.
c. Depress and hold "coast" switch and check for a reading of 114-126 ohms
d. On models with "resume," depress and hold "resume" switch and check for a reading of approx 2200 ohms.
If resistance values are not as specified, inspect wiring, slip rings, turn signal coppr brushes, speed control switch and steering column for proper ground. Check for proper ground by connection an ohmeter between upper steering column flange and a suitable ground. Resistance should be less than ½ ohm. Rotate steering wheel throughout its full range and ensure flexible coupling has a resistance of less than 1 ohm.
</DIR>Speed Sensor Test
Speed sensor can be located usually on the firewall by the actuator and has wires running down to the transmission.
Disconnect the speed sensor connector. Then connect an ohmmeter between dark green wire with white stripe and black wires. A reading of 180-250 ohms should be obtained. A reading of 0 ohms indicates a shorted speed coil and an infinity reading indicates an open coil. Replace sensor as necessary.
Servo (actuator) test
<DIR>Disconnect ball chain from throttle linkage, then the electrical connector at the amplifier.
Connect an ohmmeter between orange wire w/yellow hash and grey wire w/black hash at connector. A resistance of 40 to 125 ohms should be obtained.
Connect an ohmmeter between orange wire w/yellow hash and white wire w/pink hash. A resistance of 60 to 90 ohms should be obtained.
Reconnect ball chain to throttle.
Start engine and ensure servo vacuum from engine exceeds 2.5 in. of hg. Then disconnect servo from amplifier, at amplifier.
Connect orange wire w/yellow hash of servo to battery poitive terminal with jumper wire, and white wire w/pink hash to ground, then momentarily touch grey wire w/black hash to ground. Servo throttle actuator should pull in and engine rpm should increase. Throttle should hold in position or slowly release chain tension.
Remove white wire w/pink hash and check for immediate release of chain tension from servo.
</DIR>Note* Do not!!!Cross orange wire w/yellow hash against either white w/pink hash lead or grey black has lead. This can damage the amplifier!!
Amplifier test
"on" circuit test
<DIR>turn ignition on.
Connect a voltmeter between light blue wier w/black hash and ground or white w/purple stripe and ground.
Battery voltage should be indicated when "on" switch on steering column is depressed and held. If battery voltage is not indicated, check horn relay and perform control switch test.
Release "on" button. Voltmeter should indicate 7.8 volts indicating "on" circuit is engaged. If voltage does not remain, check amplifier ground, fuses or circuit breakers or replace amplifier with known good amplifier and repeat test.
</DIR>"off" circuit test
<DIR>Turn ignition "on".
Connect a voltmeter between light blue wire w/black hash and ground.
Depress "off" button. Voltage should drop to zero indicating "on" circuit is de-energized.
If voltage does not drop to zero, perform "control switch test"
</DIR>"Set-Acc" circuit test
<DIR>turn ignition on.
Connect a voltmeter between light blue wire w/black hash and ground.
Depress "on" switch, then hold "set-acc" button on steering wheel. Voltmeter should indicate 4.5 volts. Rotate steering wheel back and forth and check for voltmeter fluctuations. If reading varies more than .5 volts, perform "control switch test".
</DIR>"Coast" circuit test
<DIR>turn ignition "on."
Connect a voltmeter between light blue wire w/black hash and ground.
Depress "on" switch, then depress and hold "Coast" button on steering wheel. Voltmeter should indicate 1.5 volts. Rotate steering wheel back and forth and check for voltage fluctuations. If reading varies more than .5 volts, perform "Control Switch Test."
</DIR>"Resume" circuit test
<DIR>Turn ignition "on."
Connect a voltmeter between light blue wier w/black hash and ground.
Depress and hold "resume" button. Voltmeter should indicate 6.5 volts.
</DIR>Vacuum dump valve test
Locate and disconnect vacuum hose from the servo that leads to the dump valve on the brake pedal. Connect a hand vacuum pump to the hose, and draw vacuum. If vacuum cannot be obtained, the hose or dump valve is leaking, and should be replaced. If vacuum is obtained, step on brake pedal. The vacuum should be released. If not, adjust or prelace the dump valve. If still unsure, a road test can be performed. Remove the vacuum dump valve hose assy from the brake pedal mount. Clamp or tape off the end of the hose so that no vacuum can be released, nor air enter the hose. Road test the cruise control. If it works, then the dump valve is likely suspect.
Brake switch
If stoplamps function properly, chec for battery voltage at 6 way connector (amplifier) using black wier w/green stripe,or, white wire w/pink stripe or, white wire w/purple stripe.
Depress brake pedal until stoplamps are illuminated. Check voltage at red wire w/black stripe or the light green wire. The difference between the two voltage readings must not exceed 1.5 volts. If voltage is greater a high resistance exists in the circuit and must be found and corrected.
Clutch switch
Note* This switch functions magnetically. Do not use magnetized tools near this switch.
<DIR>if the switch is open when the clutch pedal is released, speed control will not operate. This must be corrected before making any other tests.
Disconnect switch pigtail connector from speed control harness connector and connect an ohmmeter to the two switch connector terminals.
With the clutch pedal in the fully released position, the resistance should be less than 5 ohms. With clutch pedal fully depressed, the circuit should be open.
If switch does not function as described, remove and replace switch.
</DIR>
Last edited by Dave Sponaugle; Feb 25, 2008 at 04:37 PM. Reason: Reduce font size
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Posting Guru
Joined: Feb 2011
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From: Princeton MN
Whats it doing? Check and make sure the vac dump valve under the dash is adjusted right. With the brake pedal released the white plunger should move all the way up into the switch. Another place to look is make sure the pickup isplugged in with good clean connections, it can be found by tracing the speedo cable. It fits between the 2 halves