| Author | Message | ||
| Tom Dessert (Mci5er)
Registered Member Username: Mci5er Post Number: 111 Registered: 12-2005 Posted From: 97.157.15.243  Rating: N/A |
So in my last post on this subject I was talking about issues my friend had with his Jakes, well mine have now quit. I found a broken wire on the buffer switch and did the repairs to correct that. In the previous post I realized that the buffer switch on my 6v92 is somewhat different than others. My govenor housing has a metal pin sticking out of it, the end of which is just short of a 1 1/4" long brown micro switch mounted on a bracket. On the micro switch are two spade lugs and a diode... one spade lug contained the two jake wires. The other single wire ran to my dash switch and 24v. I believe I have correctly repaired the wires but am not sure which wires go on which post of the switch and what that diode does. I tried to test the circuit by turning on the Jake console switch and manually depressing the contact on the micro switch and I can faintly hear clicking. Perhaps I have the wires reversed. They still don't seem to be working under power. Any ideas..... Tom | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 363 Registered: 7-2005 Posted From: 166.235.43.3 Rating: |
http://www.jakebrake.com/support/parts-and-service-literature.php?engine_mfr=3&engine_mode l=28&jacobs_product=26 http://www.jakebrake.com/service/pdf2/003879.pdf The switch should be normally closed with the engine off idle or shut down. The switch be normally open with the engine idling. Are you driving the coach to check the jakes?? The jakes won't work without built up oil pressure. That generally has to be achieved by driving. HTH, Dale | ||
| Tom Dessert (Mci5er)
Registered Member Username: Mci5er Post Number: 112 Registered: 12-2005 Posted From: 97.215.247.231 Rating: N/A |
Dale, thanks for the input. Yes, I'm driving the bus to test it. I'm here at Imperial Dam near Yuma Az not many hills around here to get a good road test. I remember that I could use it in town traffic and hear it clearly, not anymore. I get confused with some of the terminology that maybe you can help with. What is engine off idle and shutdown? I don't want to sound dumb here. Shutdown to me is engine off and off idle would be like fast idle. I want to make sure I'm electrically checking her correctly. Any idea why it has a diode on one side of the switch? Tom | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 841 Registered: 8-2006 Posted From: 74.32.95.26 Rating: N/A |
Tom, that switch should have a wire going from the side toward the front to the back terminal.Sounds like you have bad seals on the oil jumpers. good luck | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 364 Registered: 7-2005 Posted From: 166.223.74.195 Rating: |
Engine off idle is anytime the engine is being accelerated, like holding the throttle at 1000rpm. The buffer switch should read closed with an ohm meter in this case. Also when the engine is shutdown or not running the rack will go to wide open throttle. The buffer switch should read closed with an ohm meter in this case. Without the switch being able to achieve closed position, power will not be able to reach the jake solenoids. Don't know why your switch has only one diode. The ones I've seen have two diodes or none. If you have the switch with three screws, you can test across the COM & N/C terminals while the engine is being accelerated or off idle to check for continuity. Same with the two spade switch. Do not use your buses fast idle for this test. | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 842 Registered: 8-2006 Posted From: 74.32.95.26 Rating: N/A |
That switch just has one diode it is on the jumper wire. It would be nice to know if he has a high idle there are 4 different buffer switches for a DD. If he does have fast idle on a 2 stroke the switch and fast idle are 1 piece a 600.00 switch if he hears a click I doubt if it is the switch they are pretty basic power in and power out. He says he gettng a little click so it either bad soleniod,broke wiring under the valve cover or oil pressure good luck (Message edited by Luvrbus on January 26, 2010) (Message edited by Luvrbus on January 26, 2010) | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 365 Registered: 7-2005 Posted From: 166.223.74.195 Rating: N/A |
Early buffer switches were polarity sensitive and had to have the power come in on the brass or gold colored terminal. If wired wrong they would fail sometime later as the switch couldn't handle the load. These had NO diodes! The later style buffer switches are not polarity sensitive and have TWO diodes and the input and output wires can be put on either terminal. The third switch type that has a fast idle ability has a "replaceable" micro switch with three terminals with only COM & N/C being used. I so love my foot pedal switch. LOL (Message edited by happycampersrus on January 26, 2010) | ||
| Tom Dessert (Mci5er)
Registered Member Username: Mci5er Post Number: 113 Registered: 12-2005 Posted From: 97.215.157.41 Rating: N/A |
Dale, I'm still being a little thick here in my understanding. My buffer switch has two terminals that are N/O , being closed only by depressing the contactor. One terminal has a diode attached. At shutdown you will read continuity across the switch as a result of the mechanical action of the govenor closing it. At idle the govenor mechanically retracts the pin slightly opening the switch. So it appears the issue is strictly mechanical. What happens as you go down the road ? What action causes the govenor to extend the pin thus closing the buffer switch and powering the Jakes. Sorry for drawing this out. Tom | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 485 Registered: 10-2003 Posted From: 66.165.176.62  Rating: |
Tom whatyou have is exactly what my 6-71 has. That little pin is pushed on by governor. Esentially when you are driving and lift your foot off the accelrator the govenor closes the rack so that no fuel is injected into the cylinders. When the rack is in tis possition it pushes on the pin closing the microswitch and activating the jakes. As soon as you touch the throttle it opens the rack to inject fuel and the switch opens | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 367 Registered: 7-2005 Posted From: 166.235.184.203 Rating: N/A |
Ok! Your system is using a N/O switch, so when you are in a NO fuel situation (at Idle or coasting) the governor is closing the switch. There are about 15 different ways to wire up jakes. LOL Do you have a clutch pedal switch or a switch on your automatic transmission to turn off the jakes at a stop light?? Is it good? You can bypass it (jump it)and make a test pass. Just turn off the dash switch when coming to a stop because if your engine makes enough oil pressure it can stall it. If you are sure you are getting power to the jake solenoids, you may have a oil leak in between the jake heads, they need adjustment or overhaul, or some other mechanical issue. | ||
| Larry Baird (Airhog)
Registered Member Username: Airhog Post Number: 177 Registered: 1-2001 Posted From: 96.251.166.28  Rating: N/A |
This works for me.  | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1791 Registered: 12-2000 Posted From: 76.71.107.42  Rating: N/A |
Larry, FWIW, my 2001 Freightliner with a Cummins ISM is set up with the same principal. Two switches on the dash, each one activates half of the jakes, in my case, the front three and the back three. happy coaching! buswarrior | ||
| Tom Dessert (Mci5er)
Registered Member Username: Mci5er Post Number: 114 Registered: 12-2005 Posted From: 97.214.224.129 Rating: N/A |
Is no fuel condition and idle the same thing? My problem seems to be mechanical in that the governor pin isn't extending out far enough to close the buffer switch. The buffer switch is closed on shutdown by the govenor, opened when master power switch applied by the govenor and at idle the govenor pin is sitting about an 1/16 from making contact with the buffer switch. So dash switch on, 24vdc is sitting on one side of the buffer switch waiting for me to lift my foot off the accelerator and when I do the rack moves to the NO fuel position which extends the govenor pin into the buffer switch engaging both Jakes(my case). I believe this is the correct sequence but the govenor pin is falling short of engaging the buffer switch. How can I simulate it? Addition info about my configuration: I have an automatic but it doesn't have a buffer switch as part of the Jake wiring. One side of the console switch is tied to the 24vdc buss, the other side is tied directly to the buffer switch. Both of my Jake's are wired together at the buffer switch. Very simple to trace out. I realized my Jakes had stopped working. I later checked the wiring at the buffer switch found one of the jake wires broke and I repaired that. Did a test drive still no Jakes. So thats all the story I have on this. Thanks for everyones help. All ideas gladly accepted ..... Tom | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1215 Registered: 12-2000 Posted From: 173.126.190.48  Rating: N/A |
One way to test actual Jake Brake operation is to temporarily put a jumper wire across the 2 terminals on the buffer switch. Make sure the Jake Brake switch is off at the driver's seat. Go for a drive, and while cruising along, lift off the throttle and turn on the Jake Brake. It they work, you know the problem is in the buffer switch. Jack | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 487 Registered: 10-2003 Posted From: 74.251.162.133 Rating: N/A |
good test Jack. I would add if it is out of adjustment be carefull if you try to do it yourself. It's real easy to set it a little too deep and get a hanging idle or runaway. I had the guy who adjusted my rack do the buffer switch at the same time after I screwed it up | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 249 Registered: 1-2007 Posted From: 208.81.157.234  Rating: |
"Is no fuel condition and idle the same thing?" No. Idle is with the governor keeping the engine at idle RPM. Rack being partially open and controlled by the governor. Buffer switch open to prevent jake operation. No fuel is with rack closed, hence 'no fuel'. This is when you lift your foot from the throttle and the engine is still above idle RPM. Buffer switch closes to allow jake operation until engine reaches idle or you apply throttle which opens the rack and buffer switch. |
