Need help, auto electrics - Machine Underground -Tractor & Commercial Equipment Discussion Forum

Mickey · 07-01-2008, 12:45 PM

Made use of the motorhome this past week and found the cruise control on the fritz. Any one have a good understanding of the electrics for the CC? When I engage, the gas peddle heads to the floor. Doesn't matter what speed the CC is engaged. My first thought is the control is not receiving a speed signal. Seems to make sense, no signal and control thinks it needs to increase throttle so speed feedback is greater than being received. Could be the speed sensor, the wiring or be something totally different.

Any ideas? Oh, late 80's Ford chassis.

**gunmaker** · 07-01-2008, 05:15 PM

Does the vehicle have a vacuum type controller for the cruise control? If it is a vacuum type, rather than electronic (see next post) a vacuum leak could cause the system to mis-read the leak and try to accelerate until it reaches the vacuum setting called for at a given speed.

**gunmaker** · 07-01-2008, 05:19 PM

Here's a quick rundown of Ford's cruise control system, just for background.
Ford Cruise Control - How it works

Amplifier

The Amplifier (Amp) is the "brains" of the system. It simply senses road speed from the Vehicle Speed Sensor (VSS) and opens and closes the throttle to try and maintain that road speed.
Servo

The Servo contains a large diaphragm along with two solenoids and a feedback potentiometer. The diaphragm is attached by a cable to the carburetor or throttle body linkage. Engine vacuum is supplied to the Servo through a vacuum check valve which only allows vacuum to go one way.
The two solenoids are for Vacuum and Vent. One side of each solenoid is connected to battery positive with the key on. To activate a solenoid, the Amp grounds out the other side of it.
When the Amp wants to open the throttle, it activates the Vent solenoid which blocks it off. It then pulses the ground on the Vacuum solenoid to apply vacuum to the diaphragm. The diaphragm pulls the throttle open a little more each time the Vacuum solenoid is pulsed.
The Amp keeps activating the Vacuum solenoid until the desired throttle opening is reached. The Amp also uses the feedback potentiometer to determine how much the throttle is moving and bases its adjustments on that. Even if the Vacuum solenoid stops applying vacuum, the diaphragm will hold its position. It won't release the vacuum until the vent solenoid ground is released. Then the vacuum gets dumped to the atmosphere. If the Amp just wants to let the throttle go a small amount (going too fast for example) it will momentarily ground the Vent solenoid to dump a small amount of vacuum.

Vehicle Speed Sensor

The VSS is connected to the speedometer cable. Most of the later models had the speedo cable plugged INTO the speed sensor. On this type, the gear on the end of the sensor is driven by the output shaft in the transmission, and the sensor in turn drives the speedo cable. The sensor acts as a little generator. A magnet spins in a coil of wire to generate an AC voltage.

Switches

The system switches are built into the steering wheel cover. Later models have ON\OFF, SET\ACCELL, COAST, and RESUME buttons. Some of the earlier systems did not have the RESUME.

The switches have a ground circuit and also get 12 volts through the coil of the horn relay. By the way, unlike most other brands, Fords during the years that this cruise was used only had a horn relay if they had cruise. We used to get calls all the time from people looking for the horn relay on non-cruise equipped cars.
One wire goes from the switches to the Amp. I'll refer to it as the "switches" wire in this explanation.
Here's how the switches operate:
The ON button when pressed puts positive (about 12 volts) to the "switches" line.
The OFF button when pressed grounds out the "switches" line.
For the other functions, the buttons switch a resistor between ground and the "switches" line. The Amp senses the different resistances and performs the necessary function. Other Parts

Brake Light Switch

The Amp has a wire coming from the brake lights. It senses the brake light voltage when the operator steps on the brakes and disengages the cruise control.
Note: The Amp is also set to look for a resistance to ground through the brake light bulbs. As a safety feature, if it doesn't see this ground, it won't operate because it thinks the wire to the brake light switch may be broken.
Bottom line is that if both brake light bulbs are burned out, the cruise won't work. I've seen it happen a few times.
Clutch Switch
Vehicles with manual transmissions also have a switch that opens when the clutch is pushed in. This keeps the engine from revving up.
The clutch switch is wired in with the brake light switch so that it breaks the circuit to the brake light bulbs. Due to the safety feature mentioned with the brake lights above, the systems disengages.
Vacuum Dump Valve
Later systems have a vacuum dump valve on the brake pedal. A vacuum line is connected from the valve to the Servo diaphragm. When the brake pedal is pushed, vacuum in the Servo is released (dumped). This is another safety feature. In the earlier models without this valve, when the brake light switch went bad and you were using the cruise, the more you tried to stop the car the more the Amp tried to accelerate.

Mickey · 07-01-2008, 05:22 PM

Been some time since I tried to find my way around under the hood of this beast but believe it is a vac actuator. Before I start tearing into this I need to give it some thought on possible causes and lack of speed info is what came to mind for the controller to accelerate any time the CC is engaged.

Woa, looks like we were both writing at same time. This is the kind of info I was hoping for. Will have to read and digest the info and see wher to go next.

THANKS!

EDIT
If I'm reading and understanding correctly the problem could be as I suspected OR the vent valve is stuck closed and there still is the possibility the problem lies with the control board itself.

**gunmaker** · 07-01-2008, 05:49 PM

Or, if it is the older type system, the vacuum line to the cruise control unit could be the culprit.
Don't know which way to look until you can identify the type system, maybe by year? Let me know if I can help.

**gunmaker** · 07-01-2008, 06:08 PM

I thought that this might be of interest. I thought I'd pass it on rather than take a chance that you might not know of a potential problem.

Ford Parts Backlog: Owners Get Short End of the Stick

May 12, 2008. By Gordon Gibb

RSS

Del.icio.us

Seed Newsvine

Facebook

Detroit, MN: Imagine receiving a recall notice for a fairly serious problem with your Ford vehicle - one that could cause your vehicle to catch fire. So you duly respond to the recall, only to be told that there aren't enough parts, and that you'll have to wait. The parts backlog means you're continuing to drive a dangerous vehicle that could catch fire at any moment.

Even when it's just sitting, parked in the driveway.

Such is the frustration of hundreds of thousands of Ford owners who have received recall notices for faulty cruise control systems. At issue is a faulty switch that could produce a short in the electrical system. Some owners have experienced fires while driving. However, others have seen their vehicles go up in flames parked in the driveway. One family completely lost their house when their Ford Explorer caught fire in the garage. Both the truck, and the home were completely destroyed.

Ford Motor Co. has admitted that it failed to stock sufficient parts, and that it underestimated the scope and response to the safety recall. The number of vehicles is staggering. Ford has issued various recalls for repair to faulty cruise control switches since 1999. With earlier recalls, the number of recalled vehicles has been lower, given the traditional high-end status of the cruise control feature. With a lower number of vehicles, response and repair rates have been higher.

However, cruise control is being offered in more and more vehicles?even compact cars. As cruise control becomes more standardized, the numbers increase exponentially. The recalls, in lock step with availability of cruise control, spike higher as well.

At the moment?and this figure is staggering?it is estimated that 7.1 million cars and trucks are still out there with faulty cruise control switches. The risk is such that the National Highway Traffic Safety Administration (NHTSA) issued a rare, and strongly-worded advisory to owners of Ford, Lincoln and Mercury vehicles recommending they be taken to the nearest dealer and have the systems disconnected at once, until the required part is available.

"Failure to have the switch disconnected could lead to a vehicle fire at any time, whether or not the key is in the ignition, and whether or not owners use the cruise control system," NHTSA warned.

That's little consolation for a frustrated Ford owner in Mississippi, whose mother's 1988 Mercury Grand Marquis caught fire and was repaired a month BEFORE the recall notice came in. As a result, he put her into his own 1997 Lincoln Town Car, which received a recall notice for the cruise control switch in July of last year. However, when reporting to the dealer, he was told the part wouldn't be available until November. That was soon pushed back to February.

Tired of waiting, he got rid of the Lincoln Town Car and put his mother into a Lexus, instead.

Another Ford owner from Everett, Washington is completely frustrated, and disenchanted with Ford over the delay. "I feel that Ford is not being honest about the completion of the repairs for this recall. I was told in August of 2007 that the repair parts were delayed and they would be in October. That soon became February of 2008. Now I am told the dealers do not know when the parts will be available. I can not get a straight answer from anyone."

This, despite the fact that Ford maintains it is 'ramping up' the parts supply chain to finally put a dent on the remaining seven million vehicles having yet to be repaired.
The manufacturer admits it did not stockpile sufficient parts to meet what it calls unprecedented demand for repairs after the August 2007 recall, an action which saw 4,987,281 vehicles recalled. That's nearly five million. The company was overwhelmed with responses beginning in September.

That should not have been surprising. August falls within the typical vacation season. People are either away at remote locations, traveling, or in 'vacation mode' and unwilling to deal with anything that may seem even remotely complicated until after vacation season ends.

Typically, such an issue is followed-up when school starts, or when it's time to get back to work, or when normal routine resumes. It's curious as to why Ford didn't think of this, when they announced such a massive recall during the summer months. Anyone could have told them there would be little response initially, followed by a wave after Labor Day.

Lawyers say you shouldn't have to put up with that, and disconnecting the cruise control even in the short term not only robs you of a useful, gas-saving feature in this era of high gas prices, but also requires an extra trip into the dealer.

Getting rid of the vehicle is not the answer, either. Ford should be held accountable for its inability to stockpile sufficient parts to offer repairs to a dangerous situation in a timely and expeditious manner. The NHTSA has already highlighted the fact, in its warning communiqu鬠that the cruise control could erupt into flames at any time?driving down the highway with your kids in the back seat, or just sitting parked in the driveway or garage. You don't even have to use the cruise control at all, to have it present a fire hazard.

By making you wait for a replacement part, Ford is asking you to drive either without benefit of a useful and cost-saving device, or with the risk your car, truck or SUV could catch fire at any time.

The legal eagles say you don't have to put up with that. Consult a Ford parts backlog lawyer, and perhaps light a fire under Ford instead.

**gunmaker** · 07-01-2008, 06:12 PM

HERE'S SOME RECALL INFO THAT I FOUND, AND THOUGHT MAYBE YOUR VEHICLE MIGHT FALL IN ONE OF THESE CATEGORIES.

1999 Ford F350 Recall ID from NHTSA: 99V062001
Auto Recall Date: 03/30/1999
Vehicle Component: VEHICLE SPEED CONTROL
Estimated Vehicles Affected: 898739
1999 FORD F350 Defect Summary:
VEHICLE DESCRIPTION: CERTAIN 1997-1999 RHD EXPLORER EQUIPPED WITH 4.0L OHV/SOHC ENGINES AND CRUISE CONTROL BUILT FROM MAY 29, 1996 THROUGH MARCH 4, 1999; 1998-1999 EXPLORER/MOUNTAINEERS EQUIPPED WITH 4.0L OHV/SOHC OR 5.0L ENGINES OR 1998-1999 RANGERS EQUIPPED WITH 2.5L, 3.0L FFV/EFI OR 4.0L ENGINES AND CRUISE CONTROL BUILT FROM JANUARY 5, 1998 THROUGH MARCH 4, 1999; 1998-1999 MUSTANGS EQUIPPED WITH 3.8L, 4.6L 2-VALVE OR 4-VALVE ENGINES AND CRUISE CONTROL BUILT FROM MARCH 2, 1998 THROUGH MARCH 4, 1999; 1999 F250/F350/F450/F550 (OVER 8,500 LBS.) TRUCKS EQUIPPED WITH 5.4L OR 6.8L ENGINES AND CRUISE CONTROL BUILT FROM MARCH 2, 1998 THROUGH MARCH 4, 1999; AND 1999 F-53 STRIPPED CHASSIS EQUIPPED WITH 5.4L OR 6.8L ENGINES AND CRUISE CONTROL BUILT FROM MARCH 2, 1998 THROUGH MARCH 4, 1999. A CRUISE CONTROL CABLE CAN INTERFERE WITH THE SPEED CONTROL SERVO PULLEY AND NOT ALLOW THE THROTTLE TO RETURN TO IDLE WHEN DISENGAGING THE CRUISE CONTROL.
Defect Consequence:
IF THE CRUISE CONTROL IS USED AND THIS CONDITION IS PRESENT, A STUCK THROTTLE COULD RESULT, WHICH COULD POTENTIALLY RESULT IN A CRASH.
Remedy:
DEALERS WILL REPLACE THE CRUISE CONTROL CABLES. AT THE PRESENT TIME, THE REPLACEMENT CABLES ARE NOT AVAILABLE. CUSTOMERS ARE BEING ADVISED NOT TO USE THE CRUISE CONTROL SYSTEM UNTIL A REPLACEMENT CAN BE MADE.
Notes: FORD MOTOR COMPANY, 99S09

**gunmaker** · 07-01-2008, 06:15 PM

CHECK OUT THIS SITE FOR RECALL INFO:

Vehicles & Equipment | National Highway Traffic Safety Administration(NHTSA) | U.S. Department of Transportation

Mickey · 07-01-2008, 08:00 PM

Thanks for all your input. The MH is an 89 model so this recall doesn't address my problem.

Since the CC appears to work in all respects except the the constant acceleration when engaged, I'm still leaning toward something with the speed sensor/wiring or the vent valve.

Will be a little while before I can find time to address this problem but will keep the theory of operation information you provided.

Still open for other comments on possible causes.

**PaulChristenson** · 07-01-2008, 08:14 PM

Quote:

Originally Posted by gunmaker

I thought that this might be of interest. I thought I'd pass it on rather than take a chance that you might not know of a potential problem.

Ford Parts Backlog: Owners Get Short End of the Stick

May 12, 2008. By Gordon Gibb

RSS

Del.icio.us

Seed Newsvine

Facebook

Detroit, MN: Imagine receiving a recall notice for a fairly serious problem with your Ford vehicle - one that could cause your vehicle to catch fire. So you duly respond to the recall, only to be told that there aren't enough parts, and that you'll have to wait. The parts backlog means you're continuing to drive a dangerous vehicle that could catch fire at any moment.

Even when it's just sitting, parked in the driveway.

Such is the frustration of hundreds of thousands of Ford owners who have received recall notices for faulty cruise control systems. At issue is a faulty switch that could produce a short in the electrical system. Some owners have experienced fires while driving. However, others have seen their vehicles go up in flames parked in the driveway. One family completely lost their house when their Ford Explorer caught fire in the garage. Both the truck, and the home were completely destroyed.

Ford Motor Co. has admitted that it failed to stock sufficient parts, and that it underestimated the scope and response to the safety recall. The number of vehicles is staggering. Ford has issued various recalls for repair to faulty cruise control switches since 1999. With earlier recalls, the number of recalled vehicles has been lower, given the traditional high-end status of the cruise control feature. With a lower number of vehicles, response and repair rates have been higher.

However, cruise control is being offered in more and more vehicles?even compact cars. As cruise control becomes more standardized, the numbers increase exponentially. The recalls, in lock step with availability of cruise control, spike higher as well.

At the moment?and this figure is staggering?it is estimated that 7.1 million cars and trucks are still out there with faulty cruise control switches. The risk is such that the National Highway Traffic Safety Administration (NHTSA) issued a rare, and strongly-worded advisory to owners of Ford, Lincoln and Mercury vehicles recommending they be taken to the nearest dealer and have the systems disconnected at once, until the required part is available.

"Failure to have the switch disconnected could lead to a vehicle fire at any time, whether or not the key is in the ignition, and whether or not owners use the cruise control system," NHTSA warned.

That's little consolation for a frustrated Ford owner in Mississippi, whose mother's 1988 Mercury Grand Marquis caught fire and was repaired a month BEFORE the recall notice came in. As a result, he put her into his own 1997 Lincoln Town Car, which received a recall notice for the cruise control switch in July of last year. However, when reporting to the dealer, he was told the part wouldn't be available until November. That was soon pushed back to February.

Tired of waiting, he got rid of the Lincoln Town Car and put his mother into a Lexus, instead.

Another Ford owner from Everett, Washington is completely frustrated, and disenchanted with Ford over the delay. "I feel that Ford is not being honest about the completion of the repairs for this recall. I was told in August of 2007 that the repair parts were delayed and they would be in October. That soon became February of 2008. Now I am told the dealers do not know when the parts will be available. I can not get a straight answer from anyone."

This, despite the fact that Ford maintains it is 'ramping up' the parts supply chain to finally put a dent on the remaining seven million vehicles having yet to be repaired.
The manufacturer admits it did not stockpile sufficient parts to meet what it calls unprecedented demand for repairs after the August 2007 recall, an action which saw 4,987,281 vehicles recalled. That's nearly five million. The company was overwhelmed with responses beginning in September.

That should not have been surprising. August falls within the typical vacation season. People are either away at remote locations, traveling, or in 'vacation mode' and unwilling to deal with anything that may seem even remotely complicated until after vacation season ends.

Typically, such an issue is followed-up when school starts, or when it's time to get back to work, or when normal routine resumes. It's curious as to why Ford didn't think of this, when they announced such a massive recall during the summer months. Anyone could have told them there would be little response initially, followed by a wave after Labor Day.

Lawyers say you shouldn't have to put up with that, and disconnecting the cruise control even in the short term not only robs you of a useful, gas-saving feature in this era of high gas prices, but also requires an extra trip into the dealer.

Getting rid of the vehicle is not the answer, either. Ford should be held accountable for its inability to stockpile sufficient parts to offer repairs to a dangerous situation in a timely and expeditious manner. The NHTSA has already highlighted the fact, in its warning communiqu鬠that the cruise control could erupt into flames at any time?driving down the highway with your kids in the back seat, or just sitting parked in the driveway or garage. You don't even have to use the cruise control at all, to have it present a fire hazard.

By making you wait for a replacement part, Ford is asking you to drive either without benefit of a useful and cost-saving device, or with the risk your car, truck or SUV could catch fire at any time.

The legal eagles say you don't have to put up with that. Consult a Ford parts backlog lawyer, and perhaps light a fire under Ford instead.

The upside is you will get more money back from your insurance company than you will trying to sell or trade these models in...

And you can take your settlement check and go buy a fuel efficient replacement...