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Brake pressure switch question

Still hunting for my intermittent cruise control issue...could one of the brake pressure switches be failing Intermittently?

I ask this because my CC will randomly stop working while driving. Sometimes it starts working again during the drive and sometimes it won't work again until the next day. It seems to always work the next day once we take off again and the cycle starts over. At one point I thought maybe it was the ECM getting hot and affecting the CC, but I've had plenty of times when the cruise control would work for a whole day without issues, then the next day Intermittently not.work again.

So I guess I'm asking if a brake switch could be causing this.

I've been trouble shooting this for 2 years so I've already ruled out the smart wheel control box and the clock spring...among a lot of other stuff.

I could just replace all the brake switches under the dash and hope for the best. There's just the 4 correct? 2 main and 2 for back up? It doesn't look like the easiest job only because access isnt the best, but would be willing to tackle it. I did test the brake switches with my multimeter but if course it's usually when the coach has been sitting and the problem has reset so they tested ok. Guess I would have to wait for the CC to stop working, pull over and test them then.

Anyway, thanks for any insight.
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #1 –
Quote from: dlkj07 –
Still hunting for my intermittent cruise control issue...could one of the brake pressure switches be failing Intermittently?
I could just replace all the brake switches under the dash and hope for the best.
Can't offer any specific repair guidance cuz your coach is so much newer than ours.  Older coach = mechanical controls.  Newer coach = electronic controls.

I will say, based on my experience, that what you suggest sounds logical.  In almost every cruise control system, input from the brake system is required.  Brake on - cruise disengages.  In your case, with air brakes and the electronically controlled engine/transmission, the usual "input" would be a signal to the ECM from a brake line air pressure switch.  Air pressure switches can be either NO (normally open) or NC (normally closed).  To send a signal, they make or break a ground circuit or a power circuit.

Suppose the contacts in one of the brake pressure switches were to randomly "stick" in the activated position.  The switch would send a continuous "disengage" signal to the ECM, and the cruise control function would be inhibited.  Then later on, again randomly, the switch contacts reset to the normal unactivated position.  Cruise goes back to working.

"Guess I would have to wait for the CC to stop working, pull over and test them then."  This would be great, if you catch one of the switches inappropriately stuck in the activated (sending a signal) position, that would certainly confirm your suspicion.

Intermittent electrical faults are among the hardest problems to diagnose.  Which is why most service techs these days simply replace parts until the fault goes away.  It is not the most sophisticated trouble shooting solution, but sometimes you have little choice.

Good luck!
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Brake pressure switch question

Reply #2 –
I replaced to 2 round Brake light switch's. That took care of my intermittent cruise issue
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Brake pressure switch question

Reply #3 –
Quote from: bbeane –
I replaced to 2 round Brake light switch's. That took care of my intermittent cruise issue
There is four down there, which ones did you replace?..or do you only have 2?
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #4 –
It also could be you Joystick for the retarder that could be the problem. I believe it's the brake
lights coming on that disconnects the cruise. The last trip I have had the cruise disconnected a
couple of and then one time I for got to push the Joystick all the way back and it would keep
disconnecting. I have 3 air switches that look like brake light switches and they are for the retarder
under the dash and my brake light switches are under the floor.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Brake pressure switch question

Reply #5 –
Quote from: dlkj07 –
There is four down there, which ones did you replace?..or do you only have 2?
Dylan you can also Identify by the wire numbers associated with the brakes. Do you have the wiring diagram?

Re: Brake pressure switch question

Reply #6 –
Quote from: dlkj07 –
There is four down there, which ones did you replace?..or do you only have 2?
The two smaller round ones on the top. I think they are 4psl N/O 1/8"
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Brake pressure switch question

Reply #7 –
Pretty sure that 2 are brake light switches and the other 2 are for warning low air pressure. Easy to check. The brake lights switches will have power on one side and when you step on the brake the other terminal will have power. The low pressure switches will be closed with no air pressure and when you have over 60 pounds of pressure will be open b
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Brake pressure switch question

Reply #8 –
Was thinking through this...

If one of my brake switches had an intermittent issue with sticking on, wouldn't my brake lights be stuck on too when the issue arises?

When my cruise control stops working, I don't believe my brake lights are on. One reason I believe that to be true is that when towing my trailer brakes would have been smoked by now. I use the curt bluetooth wireless adapter for my trailer brakes and they apply when it sees voltage at the brake light wire in the connector.

Le me know if I'm on the right wave length here...
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #9 –
Quote from: dlkj07 –
Was thinking through this...
Let me know if I'm on the right wave length here...
I agree your deduction appears logical...which unfortunately would seem to eliminate the brake switches as the cause of your problem.

SO, back to the drawing board.  What OTHER device is capable of sending a signal to disconnect your cruise control?

In Reply #4 Peter mentioned the retarder joystick.

Where is your cruise control activation switch?  On the steering wheel?  Is there also a "disconnect" switch?

Keep mulling it over.  Eventually the solution will be revealed.


1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Brake pressure switch question

Reply #10 –
I hope I don't muddle the train of thought, but a couple thoughts:
    • I found my cruise disengagement was due to my retarder being on. I was able to narrow it down as it always seemed to disengage when I crested an overpass.  Have you found anything in common with the timing of when it disengages?
    • With this being intermittent, having a way to know if the brake lights are on "now" will be helpful.  If you have a rear camera and a toad, maybe catch the the brake light reflection off the toad?  My radio head unit dims to night mode when the headlights come on.  Hook that up to your brake lights instead so it dims when the brake lights come on.
Steve and Cassi
2007 Foretravel Nimbus 42'

Re: Brake pressure switch question

Reply #11 –
Quote from: stevej –
I hope I don't muddle the train of thought, but a couple thoughts:
    • I found my cruise disengagement was due to my retarder being on. I was able to narrow it down as it always seemed to disengage when I crested an overpass.  Have you found anything in common with the timing of when it disengages?
    • With this being intermittent, having a way to know if the brake lights are on "now" will be helpful.  If you have a rear camera and a toad, maybe catch the the brake light reflection off the toad?  My radio head unit dims to night mode when the headlights come on.  Hook that up to your brake lights instead so it dims when the brake lights come on.
I can't completely rule out the retard stick, though I have wiggled it many times and it doesn't seem to make a difference. It doesn't cause the problem and it doesn't fix the problem when I wiggle the retard stick...not sure if that helps.

As mentioned before, i'm pretty sure the brake lights are not on when the cruise control is NOT working, so there is some other force at work here.

I was able to track down and source the steering wheel contact disc for the smart wheel setup...it is in pretty bad shape so that will be the next part I throw at this...
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #12 –
There is also a relay that the retarder uses to disconnect the cruise control. Many have removed it to allow using the cruise without having the retarder off. Benefits would be rolling down a hill and having retarder come on and then resume without interruption. You may want to try that for troubleshooting to separate the two circuits. Brake lights never come on with retarder also then

Re: Brake pressure switch question

Reply #13 –
Quote from: dsd –
There is also a relay that the retarder uses to disconnect the cruise control. Many have removed it to allow using the cruise without having the retarder off. Benefits would be rolling down a hill and having retarder come on and then resume without interruption. You may want to try that for troubleshooting to separate the two circuits. Brake lights never come on with retarder also then
I have already removed the relay for the retarder to activate the brake lights...was worried I was smoking my trailer brakes when using retarder on a long gradual down hill...I did not remove the relay that disconnects the CC, only the one that applies the brake lights. I believe the wiring separates the 2 actions.
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #14 –
Quote from: dlkj07 –
I have already removed the relay for the retarder to activate the brake lights...was worried I was smoking my trailer brakes when using retarder on a long gradual down hill...I did not remove the relay that disconnects the CC, only the one that applies the brake lights. I believe the wiring separates the 2 actions.
Think that is the relay I was thinking of

Re: Brake pressure switch question

Reply #15 –
I believe that when the retarder is on it activates the brake lights and that disconnects the cruise. On
my coach I installed a Jake brake and didn't wire is up to activate the brake lights so I have to turn the
cruise off with the switch or hit the brakes to get it out of cruise for the Jake to come on. I had Cummins
set it up so the Jake will come on in cruise but it won't come on until I have speeded up to around
5 miles and hour about the cruise set point. It will stay in cruise that way but I wish it could be set with
only 1 mile an hour above cruise speed.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Brake pressure switch question

Reply #16 –
Wanted to follow up on my cruise control issue. I think I may have finally fixed it. I'm going to post this resolution in 2 posts since there was discussion about this in both.

I had previously ruled out the steering wheel "clock spring" thingy, though technically mine is not a clock spring, it's a "dual contact horn brush".

During my trouble shooting I cleaned the brass rings with contact cleaner with little success but had noticed that some of the ring was wore down to a different color. I assumed that since the two contact pins were still contacting the rings that this wasn't the problem, along with the fact that the intermittent problem didn't seam to coincide with turning the steering wheel (tilt and telescoping also). Well was I sadly mistaken.

I was going to change out my brake switches but felt like that wasn't the problem so I tackled the task of tracking down the horn brush. Foretravel didn't have the  correct part number so I eventually found it from Jtekt. I think they bought out the original manufacturer of these (Autotec), but not sure. There are 2 part numbers (the part# for mine is 1900041) and the only difference is the length of the "gap hider", the round piece that's below the steering wheel. Luckily I talked to a knowledgeable man at Jtekt and he confirmed the correct part number for my application. (I just had to measure the 'gap hider') I actually had to call Foretravel and give them the correct part number so they could order it because I couldn't order direct from Jtekt. It was $250 with shipping but well worth my cruise control working.

I'm on 2 trips with not one mishap with the CC so hopefully I didn't jinx myself by celebrating too early. We'll find out Thursday when we head to Fort Bragg.

Hopefully if someone in the future has similar symptoms they will see this post and it will save them hours of pain and anguish tracking this down.

I attached the installation instructions I recieved with the part, not a very hard job just need to follow a few key operations.
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS
 

Re: Brake pressure switch question

Reply #17 –
That is some digging down in the steering column, glad it fixed it!

What was the part number from Jtekt that you replaced?
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"

Re: Brake pressure switch question

Reply #18 –
Quote from: steve –
That is some digging down in the steering column, glad it fixed it!

What was the part number from Jtekt that you replaced?
The correct part number for my coach is 1900041.
Dylan and Aimee
2001 U320 4013
Unit# 5896
450 HP/IFS