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FC (Forward Control Unique Issues) If you have a unique issue with your FC model coach and it can't be answered in one of the other forums here, then this is where you can list it.......List your FC Parts here too.

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  #1  
Old 04-11-2010
Frank W. Frank W. is offline
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Default FC Bendix Cruise Control - add a relay

Date: April 11, 2010

Topic: Fix OEM Bendix Cruise Control low voltage.

Bus Type: 1985 BlueBird Wanderlodge FC

On a recent trip we drove at night for the first time in quite a while…headlights, marker lights, drive lights, and the stereo blasting, TV in the back on…a sustained amp load. After awhile the OEM Bendix Cruise Control dropped out and would not reset. I noted by checking solar controller digital voltage panel that my voltage was down a bit to about 12.2-12.5 volts measured at the display, which is likely much more than my cruise control unit was getting via the ignition/dash wiring.

Got me to thinking…low voltage has been well discussed as a problem for many systems wired via the dash…headlights (we already added the relays there) being a common example. I also have added relays previously for the AC fans.

At home I ran the bus with no major electrical loads “on”, and checked the drivers’ side load center (access via the outside swing away panel). There are 4 power load bars…two are hot full time, two are hot with ignition on. I found what I expected…13+ volts on the hot full time, and 11.2 to 11.5 volts on the ignition switched load bars. Easy to see that my Cruise Control unit was likely getting less than 11 volts at best, symptom of low voltage was that system just goes dead…will not set up.

The fix is to add a relay just like the headlight relay. Mr. Finn has the headlight fix written up on his site…with photos FC Modification Photo & Descriptions Of John Finn's 'Bird. As the job is so well described there…as to relay type, wiring and such, I’ll skip that and just post a photo showing the wiring harness for the CC, explain the wiring I found, and let you get to it.

Wiring as I found it: running from the twin dash switches (cruise control on/off and set/reset), there were small 18ga wires for about 12”, leading to a white push connector and transitioning at the connector to much heaver 14ga wires running down thru the load bay area to the cruise control components mounted to the rear of the battery box (see photo- holding CC harness in my fingers and you can just see the white connector).


If you figure in the already low voltage via the ign switched bus bar, all the loss from the tiny 18 ga wires used by BB at the switch...well you get the idea. The CC is starving for volts! These heaver 14 or so ga wires match the color codes and in my mind this is the end of the OEM Bendix cruise control harness. These wires are taped into one bundle and are separate from the main BB wiring bundles for the dash. They are not numbered like a BB wire harness. There was sufficient slack that I could carefully pull the wire bundle out and work on it to bridge in the new relay.

I ran a new power supply from a lower “ignition on” load center terminal - there are available circuits there - connect to fused side so you have overload protection. The ground was run to the ground bus bar - the OEM BB white wires are the grounds and in the photo can be seen on the far right. Bendix wiring harness colors: the green wire is the power supply/control circuit. The red, yellow and white wires are left alone.

I tested the voltage after this fix…13+ volts to the control unit. Nice!!! You might try this fix...you CC may be just "starving" for volts, not broken.

UPDATE: We did a lot of traveling this summer...after this "fix", the CC works fine in all modes (fast idle & cruise). My right foot is very happy!

Frank W.
Woodbridge, VA.
85FC33
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Frank W.
85FC33
Woodbridge, VA.

Coach photos & comments: http://www.wanderlodgeownersgroup.co...php?albumid=79

Last edited by Frank W.; 09-12-2010 at 07:16 AM. Reason: Added links and a smaller version photo to message body
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Old 01-01-2014
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dmurdock dmurdock is offline
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I'm getting ready to do this (and the headlight) relay update to mine - thank you for the pic and the wiring info!

Regarding the high idle, what is the proper method of activating it? I'm not sure if mine works or not because I can't make it happen (but I may be doing it wrong).
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1995 BMC37 Sold
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Old 01-02-2014
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gcyeaw gcyeaw is offline
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Quote:
Originally Posted by dmurdock View Post
I'm getting ready to do this (and the headlight) relay update to mine - thank you for the pic and the wiring info!

Regarding the high idle, what is the proper method of activating it? I'm not sure if mine works or not because I can't make it happen (but I may be doing it wrong).
When mine worked it had to be in neutral. Steping on the brake canceled it. In neutral I turned the unit on and each press of the set switch would bump the idle up a little more.
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Old 01-02-2014
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Originally Posted by gcyeaw View Post
When mine worked it had to be in neutral. Steping on the brake canceled it. In neutral I turned the unit on and each press of the set switch would bump the idle up a little more.
Does air pressure need to be up for fast idle to work? I've looked through the site and I see how air ties into the system for brakes etc...but then again I'm not even sure I'm looking at the system in the FC.
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1995 BMC37 Sold
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Old 01-04-2014
Frank W. Frank W. is offline
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Yes...you need to run the main engine a few minutes and build up some air pressure for the cruise control to work. I'd say if you can flip open/close your dash vents or move your seat side to side...the cruise control should work as far as needed amount/pressure of air.

As mentioned...you turn system "on", then as I recall ('cause bus is covered), Transmission in N, depress "set", then adjust idle up with repeated pressing of "resume"...idle should go up about 150-200rpm per press.
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Frank W.
85FC33
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Coach photos & comments: http://www.wanderlodgeownersgroup.co...php?albumid=79
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Old 01-04-2014
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dmurdock dmurdock is offline
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Quote:
Originally Posted by f.wernlein View Post
Yes...you need to run the main engine a few minutes and build up some air pressure for the cruise control to work. I'd say if you can flip open/close your dash vents or move your seat side to side...the cruise control should work as far as needed amount/pressure of air.

As mentioned...you turn system "on", then as I recall ('cause bus is covered), Transmission in N, depress "set", then adjust idle up with repeated pressing of "resume"...idle should go up about 150-200rpm per press.
OK next time I'm out there I'll give it a shot...I think I've been doing everything you describe except hitting resume, I think I've been hitting set over and over. Thanks!
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1995 BMC37 Sold
1984 FC35RB Sold
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Old 05-16-2018
Boise_Wannabee Boise_Wannabee is offline
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I have started to troubleshoot my cruise today. I spent most of the day chasing a lack of voltage at the switch, only to discover I'd goofed up and actually had voltage, just not very much. 8 volts at the set side of the second switch.

I will have to try this mod to see if I can resurrect the Bendix cruise. Any other possible failure points to troubleshoot. Cruise is a must for me but I can't pull the trigger on a Cruise King.

Thanks.
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1985 FC35SB
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Old 05-29-2018
Frank W. Frank W. is offline
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Good luck on this project.

Once you get the low voltage issue resolved, you likely need to check the wiring at the control unit box. This box is located behind the main battery box/tray and is accessed by removing the cover which screws/bolts to the rear side of the battery box/tray.

When I checked mine, I did find one wire that had insulation missing at a rub spot, and a couple of years later dug in and fixed an air leak at a fitting in this area also.
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