94 U280 Pac Brake Switch

Topic: 94 U280 Pac Brake Switch (Read 2521 times) previous topic - next topic

Re: 94 U280 Pac Brake Switch

Reply #50 – May 31, 2019, 01:11:45 pm

One thing I forgot to mention is that the main shut off switch is the same rocker switch in the same location as most coaches that is used for the retarder activation on the dash but is unlabeled at this point in time. So yes, you do have the ability for coasting as long as you have the slope. I'm hoping that there is a single wire hookup to the transmission ECM that can be used as it is very close to the switches on the dash and by the accelerator pedal. If anyone knows please chime in with your opinion in as it would be much appreciated. I had thought about a secondary switch that could be inline to the transmission so if I decided it was not necessary I could override it but that is just an idea at this moment as it may not even be necessary.

Re: 94 U280 Pac Brake Switch

Reply #51 – May 31, 2019, 01:14:49 pm

John,

Pacbrake's website has those diagrams.

But, interface with the Allison ECM is not necessary-- some may even say detrimental. There is no ideal "pre-select gear" for exhaust brake use.

Going west into Albuquerque on I40, 5th gear is perfect. Coming to a complete stop, 2nd gear is perfect.

You certainly have the option of not interfacing with the Allison and just using the down arrows to select the proper gear.

Re: 94 U280 Pac Brake Switch

Reply #52 – May 31, 2019, 02:00:27 pm

Thanks Brett, I'll leave well enough alone for now. It has worked fine for me in the past.

Re: 94 U280 Pac Brake Switch

Reply #53 – May 31, 2019, 04:41:10 pm

The pac brake switch is wired on top of the throttle in the engine compartment. Hot and ground, that's all. It causes the air system to open and close the butterfly to cut off exhaust. In order for it to work it's necessary to step on the brake pedal. If the dash rocker is on and lit up, then the pac brake is activated. When you apply throttle the pac brake opens until you let off the throttle again. It won't work at all in cruise control unless you tap the brake pedal to kill the cruise. The higher the rpm's I guess the better it works. Hope you like yours better than I like mine.

Re: 94 U280 Pac Brake Switch

Reply #54 – May 31, 2019, 05:30:38 pm

I ripped out the switch on the engine and used a new switch shown in the previous photos on the accelerator pedal. It is wired basically the same as it was before but in a much cleaner location up front. Someone had rewired it exactly the same as the original wiring, duplicated more or less and there was nothing wrong with the original wiring except the original PacBrake switch at the fuel pump was sticking from dirt or corrosion so it is now gone and returned back to the original wiring. Now it is functional as before.

As everyone notes it is not a jake brake but more an assist only much the same as my car has. If you plan far enough down the road it works well but for quick stops not so much. In any case that is why we have good service brakes and try to keep them that way.

John

Re: 94 U280 Pac Brake Switch

Reply #55 – May 31, 2019, 05:42:41 pm

I assume you have a 'PRXB" model? Here's one in our CAT: Brett did a cool thing when he modified the shifter console; the toggle switch is on the bottom, perfectly placed for my left hand! I've got some files I'll dig up about the lube type and locations, maybe someone else will chime in. BTW, I LOVE ours!

Re: 94 U280 Pac Brake Switch

Reply #56 – May 31, 2019, 05:51:13 pm

PacBrake Lube: SuperLube - Exhaust Brake Lubricant | Pacbrake

Picture on the right shows where to lube. If not a PRXB brake, lube only the "places" that your exhaust brake has.

Re: 94 U280 Pac Brake Switch

Reply #57 – May 31, 2019, 05:53:41 pm

Quote from: Parati – May 31, 2019, 05:30:38 pm

As everyone notes it is not a jake brake but more an assist only much the same as my car has. If you plan far enough down the road it works well but for quick stops not so much. In any case that is why we have good service brakes and try to keep them that way.
John

Ya gotta love them 4 wheel discs.

Re: 94 U280 Pac Brake Switch

Reply #58 – May 31, 2019, 06:05:34 pm

Thanks but I already have the info from PacBrake on all the lube points and have been doing it religiously for 6 years now even when it was not working so it did not become a boat anchor. I do it before I take it out and also when I put it in storage just to be safe. Lube is cheap and a lot less work than replacement of parts.

Re: 94 U280 Pac Brake Switch

Reply #59 – May 31, 2019, 06:12:46 pm

John,

You are the rare exception-- most exhaust brakes are NEVER lubed and just seize up.

Re: 94 U280 Pac Brake Switch

Reply #60 – May 31, 2019, 06:27:15 pm

Quote from: wolfe10 – May 31, 2019, 06:12:46 pm

You are the rare exception-- most exhaust brakes are NEVER lubed and just seize up.

X2 John! For those who need 'em here's the scoop:

Re: 94 U280 Pac Brake Switch

Reply #61 – May 31, 2019, 07:49:36 pm

My exhaust brake shaft slides up a down out of the exhaust airstream will dry Teflon spray lube gum up? Valve body will eventually heat up to approach normal exhaust temp's of which I have no clue. Donaldson shows my peak temperature at 850. No pyrometer or boost gauge, probably will add the boost on my coach to help judge fuel use. Do have an exhaust manifold pressure gauge redlined at 29 psi.

Re: 94 U280 Pac Brake Switch

Reply #62 – May 31, 2019, 08:18:29 pm

I'm learning, too. Things I did not know about our PB:

Re: 94 U280 Pac Brake Switch

Reply #63 – May 31, 2019, 08:36:23 pm

More good PB stuff:

Re: 94 U280 Pac Brake Switch

Reply #64 – May 31, 2019, 08:38:26 pm

We were really interested in a pac brake when we first got our coach. I talked to the guys at pac brake and they didn't want to sell us one because they believed that with our transmission (MT647) the performance would poor enough as to not justify the expense. We were also having trouble finding a shop that would install it due to liability issues.

Re: 94 U280 Pac Brake Switch

Reply #65 – May 31, 2019, 08:40:19 pm

Quote from: The Soft Boulders – May 31, 2019, 08:38:26 pm

We were really interested in a pac brake when we first got our coach. I talked to the guys at pac brake and they didn't want to sell us one because they believed that with our transmission (MT647) the performance would poor enough as to not justify the expense. We were also having trouble finding a shop that would install it due to liability issues.

Looks like they make a by-pass for the Allison. See my post above.

Re: 94 U280 Pac Brake Switch

Reply #66 – May 31, 2019, 11:43:07 pm

I'm thinking that I'll just forget about the Allison wiring as I did not need it before and I would only be using it on the steep downgrades which is all I had used it for before and it was just fine. The Super Lube is in the coach at all times under the bed, handy. I think I might throw on a flasher on the rocker switch illumination as I have about 6 of them and that would make sure I don't forget to shut it off. It sure beats that darned toggle switch that was put in as that would get left on a number of times as it is so small that you don't notice the position and it is not in plain sight. I'll see how it goes as the ECM switch is pretty much what I was thinking of doing but I'll see how well it and myself operate first on the new setup. It is funny that they already have the switch for those who might want it so the call for it seems great enough they had to make it. It all comes down to operator errors in the end anyway for the most part and I'm no exception. If you are operating it in low speed conditions as Brett noted that puts a whole new issue on the table for manual selection. I had never thought about using it for traffic conditions myself but if it works that is great as the service brakes would see a lot of use otherwise, especially in Seattle rush hour traffic which starts at midnight and ends at midnight, almost. Thank heaven for the express lanes!

Re: 94 U280 Pac Brake Switch

Reply #67 – June 01, 2019, 08:46:04 am

John,

Unless your PacBrake is a LOT more effective than mine, I think you will find it has very little discernible effect when driving in traffic, because most of the time engine is barely above idle. Leaving it engaged all the time won't hurt anything, but don't think it will make much difference in your brake usage (in normal city driving).

Exhaust brakes work best at high engine RPM. Yes - I know - the PacBrake uses a design that increases the efficiency over a wider range of RPM. My Super Duty exhaust brake has the same basic design feature. Still doesn't do much, if anything, driving around town.

D-Celerator Diesel Exhaust Brake

The GOOD thing about having it ON all the time (should you do so) is it keeps it exercised and freed up and ready to use in the mountains.

Re: 94 U280 Pac Brake Switch

Reply #68 – June 01, 2019, 11:47:12 am

Quote from: Chuck & Jeannie – June 01, 2019, 08:46:04 am

Unless your PacBrake is a LOT more effective than mine, I think you will find it has very little discernible effect when driving in traffic, because most of the time engine is barely above idle. Leaving it engaged all the time won't hurt anything, but don't think it will make much difference in your brake usage (in normal city driving). The GOOD thing about having it ON all the time (should you do so) is it keeps it exercised and freed up and ready to use in the mountains.

Unless I have to come to a full stop, I toggle the PB back and forth in downtown traffic; works great!. The model I have will provide braking down to low RPMs.

Re: 94 U280 Pac Brake Switch

Reply #69 – June 01, 2019, 05:51:44 pm

Being that mine is the early model and not the new two stage I have to agree. I think that was the case but I have not used it in while and that stands to reason as you seldom get above idle, especially if you get caught in Seattle rush hour going the opposite the express lanes depending on the time of day. I guess for that the anchor on the rear works best for that.

Re: 94 U280 Pac Brake Switch

Reply #70 – June 01, 2019, 06:03:30 pm

Quote from: Parati – June 01, 2019, 05:51:44 pm

Being that mine is the early model and not the new two stage I have to agree. I think that was the case but I have not used it in while and that stands to reason as you seldom get above idle, especially if you get caught in Seattle rush hour going the opposite the express lanes depending on the time of day. I guess for that the anchor on the rear works best for that.

Pacbrake has a web site and is on Face Book with quick service for questions. I'd wonder what the upgrade using your existing would cost? I also saw, on their site, a list of authorized service outlets. Heck, the factory is just up the I-5 from Seattle!

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