Brake Lights

Lin · January 05, 2014, 05:40:43 PM

My brake lights (as well as the brake telltale) stay on. I assume it is the brake light switch being bad or just stuck). Is it on the brake valve? By the way, I did try pulling up on the pedal, but it didn't help.

Another question-- Although the air system seems to be fine, it seems to me that the system loses air rather quickly if I am maneuvering through something like a multi-stop U-turn. Any suggestions there? Thanks

PP · January 05, 2014, 08:02:16 PM

This may sound stupid, it is late here, but my brake lights are on whenever I set the parking brake, which is whenever I'm not in the driver's seat. Is that the case? Or are you leaving it running in nuetral with the parking brake off? That would be the only way I can check mine unless I send the DW back there, which is what we do before hitting the road.
Just a thought and probably way off base,
Will

One other thing, the brake light switch on mine is a pressure valve in the air line up front. I know because I had to replace it once.

Lin · January 05, 2014, 08:55:00 PM

Yes, the brake lights and telltale do go on when either the parking brake or service brake is applied. This is happening when both are not being applied. I, of course, knew that the telltale was on while driving. I did have to go out and look in the back with both brakes off to verify that the brake lights were on also. To be safe, I put it in first gear so I could catch the bus once I had checked.

PP · January 06, 2014, 08:38:09 AM

Quote from: Lin on January 05, 2014, 08:55:00 PM
I did have to go out and look in the back with both brakes off to verify that the brake lights were on also. To be safe, I put it in first gear so I could catch the bus once I had checked.

You have a very dry sense of humor (I hope) LOL
Will

Rick 74 MC-8 · January 06, 2014, 03:07:56 PM

Start with the bulbs.

Rick

gus · January 06, 2014, 03:58:11 PM

If you have double contact bulbs sometimes they can get crossed up in the sockets when the bulb tangs get pushed in, then they cause all kinds of weird things.

Lin · January 06, 2014, 06:40:43 PM

Well, this turned out to be a twofer. The parking brake light switch failed and had a substantial air leak. The service brakes have their own switch and that one is working fine. What itramounts to is that the parking brake light switch is normally closed, so since that is the switch that failed, I must have been driving with the brake lights on all the time.

I got a brake light switch from Napa that, although different looking, I thought would work. Anyway, that one turns out to be normally open (as the service brake light switch is) so it will not do. Tomorrow I hope they can get me the right one. If anyone knows the part number for that, it may help. Thanks

PP · January 06, 2014, 06:47:34 PM

Hey Lin, hope that resolves it. You're right about it being normally closed, it takes air pressure to turn the lights off. The NAPA guy was able to cross reference the number on the side of mine to come up with one that worked, but I'm not sure if your MC-5 would have the same pipe fitting sizes even if the pressure specs are the same. Good luck with that, Will

luvrbus · January 06, 2014, 06:56:11 PM

You buy those by the number of lights used for the stop lights Bendix 274746-SL4 for 4 lights and 2 wire terminals

good luck

Lin · January 06, 2014, 09:29:48 PM

My brake lights have just one bulb each. Would you count the telltale to make it a total of three lights? I assume that a switch rated for 4 bulbs will handle a lower number too.

luvrbus · January 07, 2014, 02:21:49 AM

Lin,the SL-4 works on a 2 light system the SL-2 won't last on a 4 light system the guy sold you a low air pressure warning unit they look the same fwiw

Lin · January 07, 2014, 08:06:15 AM

Maybe Clifford, I think the low pressure switch had a 1/8 npt. He said this one is for the service brake, therefore normally open. The number you gave is a great help. It seems that they have modified the part and number to come up with this:

http://www.anythingtruck.com/product/060-274746N.html

Hopefully Napa can get one quickly.

B_K · January 07, 2014, 11:25:36 AM

If all it does is turn the brake lights on when parked why not eliminate it? (I don't don't like having brake light on just because it's parked and running)
A pipe plug should do the trick.

BK

PP · January 07, 2014, 12:37:12 PM

Quote from: B_K on January 07, 2014, 11:25:36 AM
If all it does is turn the brake lights on when parked why not eliminate it? (I don't don't like having brake light on just because it's parked and running)
A pipe plug should do the trick.
BK

And a short jumper wire to close the circuit. (Sounds like something I would do) LOL
Will

Lin · January 07, 2014, 01:47:22 PM

Bk-I thought of that but somehow always think that if God created the 5a like that, He must have had a reason. Actually it is worse than the brake lights being on while the bus is parked and idling. They are on whenever the master switch is on.

Plugging it though, may be the thing to do and see whether it makes any difference to me. I assume it would put less wear on the stop light relay for one thing.

PP- You would not want the jumper wire since that would leave the brake lights on all the time. It is a normally closed switch.

I contacted Bendix to verify that the above number would work. It turns out that that one is also normally open so would not be good. They gave me a number (276185N) that is normally closed up to 12 psi. I checked online and it looks just like the one I removed.

Replacing parts with this old machine rarely turns out to be without including a few bumps.