King Controls wire connections and brake switches

Topic: King Controls wire connections and brake switches (Read 1089 times) previous topic - next topic

King Controls wire connections and brake switches

May 29, 2022, 02:16:24 pm

I'm not ready yet to tackle swapping out the King Controls throttle for an air throttle in my '98 U295. I'm trying some of the other suggested fixes for throttle response issues first, namely replacing the wiring connectors immediately adjacent to the King Controls actuator under the bed, and cleaning or replacing the brake switches and relay in the squirrel cage compartment under the driver's seat.
The brake switches as seen in the first 3 pics - do these look like they should be replaced, or can they just be cleaned up? If replacing I assume I'd need to bleed the air down first? Anything else I should know about replacing these? And does anyone have a part number and/or link to where to get them?
The fourth pic is of a lonesome wire without a mate just hanging out on top of the radiator in that same compartment. Any ideas what that is?

Re: King Controls wire connections and brake switches

Reply #1 – May 29, 2022, 06:45:05 pm

The brake switches only have pressure on them when you depress the brake pedal.

Re: King Controls wire connections and brake switches

Reply #2 – May 29, 2022, 07:43:03 pm

Those switches don't look too bad. If they are working why change them.

Re: King Controls wire connections and brake switches

Reply #3 – May 29, 2022, 08:39:31 pm

I would take the nuts off and clean them then apply dielectric grease to them and re assemble
A little cleaning never hurts when it comes to electrical connections
Chris

Re: King Controls wire connections and brake switches

Reply #4 – May 30, 2022, 10:20:58 am

Have a hard copy of the King control owners manualKC-2600,it has a wiring diagram,am willing to scan the diagram and send
and/or take the whole 22 page manual to office depot to copy and send,let me know.If there is a interest in a few copys will probably be less expensive.

Re: King Controls wire connections and brake switches

Reply #5 – May 31, 2022, 10:56:46 am

Quote from: John44 – May 30, 2022, 10:20:58 am

Have a hard copy of the King control owners manualKC-2600,it has a wiring diagram,am willing to scan the diagram and send
and/or take the whole 22 page manual to office depot to copy and send,let me know.If there is a interest in a few copys will probably be less expensive.

Thanks John I found the owners manual and a couple versions of the wiring diagram so I'm all set.
I've just finished replacing all the wiring connectors and cleaning and shining the terminals/connections to the brake pressure switches. Hoping for the best now!

Re: King Controls wire connections and brake switches

Reply #6 – June 05, 2022, 04:05:37 pm

Update: The coach failed its test ride today.
Drove beautifully for the first 20 miles - responding perfectly to throttle. Looping around on the slower back roads, then onto the freeway for return to home, cruising at 60mph all of a sudden lost all throttle response. Stopped in the breakdown lane, played with reseating the electrical connections under the bed, verified that King Control unit is limiting its pull to 1/3 by watching as copilot up front exercised the accelerator pedal. Max RPM's 1,100. Manually pulling on throttle I can generate 2,500 RPM or more.
So we limped the last mile and a half at 8 MPH to the freeway exit, left the coach in the Tractor Supply parking lot, and continued home in the Jeep which we brought along "just in case."
I'm about ready to pull the trigger and order all the parts to convert it over to an air throttle. But first, I want to eliminate the possibility that the King Control unit is functioning properly and the problem lies with the brake light wiring. The trouble shooting guide tells us that this 1/3 throttle symptom is caused by "brake circuit is open or is bleeding voltage to the actuator" and the actuator "must 'see' ground through the brake circuit to actuate properly."
How do I test for this?
If the problem doesn't magically (and temporarily) disappear when I return to it this afternoon, which it has done in the past, then I'm planning to return to it again at 4am when there is little traffic and limp it the remaining 7 miles back to the house.

Re: King Controls wire connections and brake switches

Reply #7 – June 05, 2022, 05:24:35 pm

First of all, nobody should have to limp far or be towed as there are temporary ways to activate throttle by pulling on injector pump throttle lever, the same lever that King pulls on electronically.

We made a bypass mod and here is description, with wiring diagram attached...

King system is also connected to brake light circuit. Sensing brake lamp voltage,
throttle will automatically go to zero (idle) position. Cruise control uses brake light
voltage sensing to turn cruise off.

A 12-volt incandescent-bulb lamp is mounted on front of bed. This added lamp serves
several functions. It turns on when brake light wiring has 12-volt positive letting driver
know that outside brake lights are working. With rear brake lights now being LED, the
lamp ensures that throttle control will see a required ground through the bulb
filament. Also, an emergency bypass toggle switch on lamp can disconnect King from
brake light wiring to allow driving with 'stuck' brake air pressure switch.

Brake voltage is important to the operation and King must be sure it is wired to brake
light circuit. When brake light voltage is not present (foot off brake pedal, etc) system
must 'see' ground potential through brake light bulbs. So, in other words, throttle
control system must see 12-volts positive OR 12-volts negative on brake light wire.

If the negative ground is not found, cruise will not turn on, and no matter how far
throttle pedal is pressed, engine will only work with a low throttle RPM position that is
called "Limp-mode".

If it sees 12-positive, throttle system will not work. Using bypass toggle switch is a
throttle workaround for a stuck brake light switch BUT using cruise control in this
bypass mode is dangerous as pressing brake will not turn off cruise.

B

Re: King Controls wire connections and brake switches

Reply #8 – June 05, 2022, 06:17:37 pm

Quote from: Barry & Cindy – June 05, 2022, 05:24:35 pm

First of all, nobody should have to limp far or be towed as there are temporary ways to activate throttle by pulling on injector pump throttle lever, the same lever that King pulls on electronically.
Brake voltage is important to the operation and King must be sure it is wired to brake
light circuit. When brake light voltage is not present (foot off brake pedal, etc) system
must 'see' ground potential through brake light bulbs. So, in other words, throttle
control system must see 12-volts positive OR 12-volts negative on brake light wire.
If the negative ground is not found, cruise will not turn on, and no matter how far
throttle pedal is pressed, engine will only work with a low throttle RPM position that is
called "Limp-mode".

I understand all this, and I even have the emergency "drive-by-string" equipment in the coach, but that's a 2-person job to use it and I didn't want to leave my Jeep stranded on the highway for any length of time. (We weren't towing it at the time.)
What I don't understand is how I go about testing the "ground potential through brake light bulbs".

Re: King Controls wire connections and brake switches

Reply #9 – June 05, 2022, 06:22:16 pm

"Drive by string" CAN be done by one person. Legal disclaimer-- I don't recommend it.

2' of PVC pipe at foot of the bed to run the string through-- close the bed on it. String to driver's area.

Fail safe is to just turn off the key and coast to the side of the road.

Have driven several hundred miles like that. Recommend it? NO. Done it? YES.

Re: King Controls wire connections and brake switches

Reply #10 – June 05, 2022, 07:10:58 pm

Drive by emergency wire.
I made up a temporary rig to get me to safety.
Drilled two holes under the bed front walls, and fed a coated cable with a loop on each end. On the engine end I tied a short line. On the other end I attached the loop to a small c clamp at the top of the foot throttle pedal. After attaching the c clamp end, I threaded the short line thru the throttle spring on the fuel pump attachment.
I can now drive by foot feed in about 2 minutes if I need to. The cable is kept coiled in the space below the electrical panels, pre threaded thru the front and aft platform walls. The clamp and string at ready to connect.
I have the air throttle bracket kit on its way, and will next be ordering and installing an air throttle system.

Re: King Controls wire connections and brake switches

Reply #11 – June 05, 2022, 07:44:38 pm

By far the most critical issue with "drive by string/wire" is how comfortable are with machinery.

If you are a "MacGyver-type" this works just fine.

If you are a "put in D and go" please do NOT try this!

Re: King Controls wire connections and brake switches

Reply #12 – June 05, 2022, 07:49:08 pm

We're getting off track here. I'm looking for someone to tell me how to test the path to ground through the brake light system.

Re: King Controls wire connections and brake switches

Reply #13 – June 05, 2022, 09:41:27 pm

Every incandescent 12v bulb has a filament where one side is connected to ground. The other side of the filament is connected to 12v positive via a switch.

When switch is off and 12v positive is not flowing, one can measure to see if there is a ground. If bulb filament is broken, the positive side will not see ground and if powered with 12v positive bulb will not light.

King has a connection to the 12v positive side of the bulb...

If it sees ground, it knows 12v positive switch is open and bulb is in place, so it decides it must be connected to a working brake light circuit, so it can act when brake lights are lit.

If it does not see ground, it must assume it is not connected to a brake light and will never know if brakes are applied.

If it sees 12v positive, it assumes brakes are being applied, so it better retract throttle cable, and if cruise control is active, it will also turn cruise off.

To measure for ground potential, use a voltmeter in 12v DC scale with red lead on a known 12v positive and black lead on the King wire that is connected to brake lamp. 12v on meter indicates ground potential is correct.

But any circuit may not be consistent if a wire connection or bulb contact is not clean or problematic. So a test could be correct, but later fail when going over a bump in the road.

B

Re: King Controls wire connections and brake switches

Reply #14 – June 06, 2022, 09:25:54 am

Quote from: Barry & Cindy – June 05, 2022, 09:41:27 pm

Every incandescent 12v bulb has a filament where one side is connected to ground. The other side of the filament is connected to 12v positive via a switch.

When switch is off and 12v positive is not flowing, one can measure to see if there is a ground. If bulb filament is broken, the positive side will not see ground and if powered with 12v positive bulb will not light.

King has a connection to the 12v positive side of the bulb...

If it sees ground, it knows 12v positive switch is open and bulb is in place, so it decides it must be connected to a working brake light circuit, so it can act when brake lights are lit.

If it does not see ground, it must assume it is not connected to a brake light and will never know if brakes are applied.

If it sees 12v positive, it assumes brakes are being applied, so it better retract throttle cable, and if cruise control is active, it will also turn cruise off.

To measure for ground potential, use a voltmeter in 12v DC scale with red lead on a known 12v positive and black lead on the King wire that is connected to brake lamp. 12v on meter indicates ground potential is correct.

But any circuit may not be consistent if a wire connection or bulb contact is not clean or problematic. So a test could be correct, but later fail when going over a bump in the road.

B

Great explanation, thanks Barry.
My problem now is that the problem is intermittent. Yesterday I returned to the coach after it sat 4 hours at Tractor Supply, and it ran just fine long enough to get me 7 miles closer to home, but still 2 miles from the house. I let it sit another 4 hours on the side of the road, went back again and it ran fine and now sits in the driveway.
I could hook up the aux 12v light Barry has done and my understanding is that it would provide an alternate path to ground, thus eliminating the check on brake lamp switches and brake lamps. That would work for me, IF the problem I'm experiencing is being caused by funky brake light wiring. Obviously that's hard to test for when the system is working properly.

Re: King Controls wire connections and brake switches

Reply #15 – June 06, 2022, 11:09:16 am

Knowing nothing About the King control but something about electricity you seem to have a bad connection rather than a mechanical problem. Using a volt meter can show voltage and grounds but not current. Trouble shooting an electrical connection problem is difficult. Physically check all your connections including connecter plugs cleaning them as you go.

Re: King Controls wire connections and brake switches

Reply #16 – June 06, 2022, 11:26:47 am

Quote from: craneman – June 06, 2022, 11:09:16 am

Knowing nothing About the King control but something about electricity you seem to have a bad connection rather than a mechanical problem. Using a volt meter can show voltage and grounds but not current. Trouble shooting an electrical connection problem is difficult. Physically check all your connections including connecter plugs cleaning them as you go.

I agree and in studying both the King Controls installation and user manual as well as the diagnostics flow chart, I see the phrase "1/3 throttle" mentioned multiple times but only one explanation for it each time, and that is faulty brake light wiring. So I'm going to install the alternative path to ground as Barry has documented and then get out and test drive as many times as I can before leaving on our cross country jaunt July 1st.

Re: King Controls wire connections and brake switches

Reply #17 – June 06, 2022, 11:28:50 am

I am not familiar with the King system, but reading up on it, it's an interesting system.

Also, if it is the brake lights/ground, you could replace all of your taillight bulbs in case there is a short there, that would be inexpensive. When you drive back, can someone follow you in your Jeep and if/when it acts up, use your phone or walkie-talkie to see if the brake lights are working? This would also ensure you have transportation if you need to drive somewhere and leave the FT on the side of the road.

If you do decide to upgrade to an air system, what options are out there? Who do people use? And do you know when the last of these were installed?

Re: King Controls wire connections and brake switches

Reply #18 – June 06, 2022, 11:56:14 am

Quote from: Jason – June 06, 2022, 11:28:50 am

I am not familiar with the King system, but reading up on it, it's an interesting system.

Also, if it is the brake lights/ground, you could replace all of your taillight bulbs in case there is a short there, that would be inexpensive. When you drive back, can someone follow you in your Jeep and if/when it acts up, use your phone or walkie-talkie to see if the brake lights are working? This would also ensure you have transportation if you need to drive somewhere and leave the FT on the side of the road.

If you do decide to upgrade to an air system, what options are out there? Who do people use? And do you know when the last of these were installed?

Yes my wife was following in the Jeep yesterday and she claims that the brake lights were working through all this. So I'm assuming if there's a fault it's not in the brake lights or the bulbs but between the King Controls box and those items.
There is a complete writeup of how to do the conversion here.

Re: King Controls wire connections and brake switches

Reply #19 – June 06, 2022, 08:25:35 pm

Jason,

Early RV manufacturers, including Foretravel used a popular non-computerized Cummins C8.3 engines. Most installed air throttles and King for just cruise control. There were thousands of these coaches in service.

Inventor / owner Lael King is an innovative guy and, on his way, to inventing the satellite King Dome antenna, he promoted a mod to his existing cruise control by adding throttle control, thus eliminating the air throttle setup by just changing the throttle pedal.

This throttle / cruise control King box was installed in all coaches using the C8.3 engines. When Cummins introduced the computerized ISC 8.3 engine in about 1998, King throttle / cruise control were no longer being used.

Lael King decided with coach manufacture demand going away, he did not want to support the product anymore. King's tech in charge of the product left the organization and built his own business selling the product to truckers and RVers using non-computerized engines, mostly selling cruise control and repairing existing throttle / cruise control boxes. Many of us have visited his place of business.

Then a few years ago with parts being difficult to obtain, and profits falling, with nobody wanting to buy the business, our only supplier and servicer of King Control went out of business.

There have been a few electronic replacement ideas, but no company stepped up to fill the need, probably because they did not understand the market need.

B

Re: King Controls wire connections and brake switches

Reply #20 – June 06, 2022, 08:58:00 pm

I think that it might be a heat issue in the King control box. A friend of mine put a fan on his to keep it cool and that fixed it for him. Just another idea.

Re: King Controls wire connections and brake switches

Reply #21 – June 06, 2022, 09:11:18 pm

A fan, what a good idea...

Re: King Controls wire connections and brake switches

Reply #22 – June 07, 2022, 02:12:35 pm

If the brake lights are on the King controller will only give 1/3 throttle. I had a problem with
the Monaco I had, something was making the brake lights come on so out of cruise and no power.

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