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77 R100RS Rear MC Fluid Level Switch
77 R100RS Rear MC Fluid Level Switch
I have been refurbing my rear brakes and came across the MC Reservoir Level Switch. This is a normal open switch and i guess it works by it being closed when the brake fluid level comes in contact with the switch. But the max level for the reservoir is below the switch so i am confused how this would work.
I have checked the wiring diagram and it brings on my dash light when it closes.
Can anyone help me out with our explanation.
Thanks kingcowie
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project
- schrader7032
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Re: 77 R100RS Rear MC Fluid Level Switch
My /7 only has the under tank reservoir. I would think that the rear reservoir would work the same in that the fluid would raise up a float that was inside the reservoir, thus opening the circuit to the light and turning it off. If the fluid drops down, the float comes down, and thus closes the circuit, lighting the light.
Is there anything inside your reservoir when you take the cap off?
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Re: 77 R100RS Rear MC Fluid Level Switch
There is no float to activate the switch.
Just the two contacts
i will get a picture today.
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project
- schrader7032
- Posts: 9056
- Joined: Fri Oct 27, 2006 3:00 am
- Location: San Antonio, TX
- Has thanked: 3 times
- Been thanked: 36 times
Re: 77 R100RS Rear MC Fluid Level Switch
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Re: 77 R100RS Rear MC Fluid Level Switch
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project
Re: 77 R100RS Rear MC Fluid Level Switch
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project
- schrader7032
- Posts: 9056
- Joined: Fri Oct 27, 2006 3:00 am
- Location: San Antonio, TX
- Has thanked: 3 times
- Been thanked: 36 times
Re: 77 R100RS Rear MC Fluid Level Switch
I'll just say that the undertank reservoirs had to have an electrical circuit to it because, well, it was covered by the tank and not readily visible. Later when the handlebar reservoir came into use, no electrical circuit because it was easy to look down and see what was there. I suspect the same thing with your rear brake reservoir...it's readily visible so it doesn't need any wires to it. It has outlets on the bottom to feed the master cylinder. That seems to be consistent with replacement parts shown on the EME website.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
- srankin
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Re: 77 R100RS Rear MC Fluid Level Switch
You are missing the float inside the cap, At least, I don't see it in your pictures. No float, the system will not work as it should.
- srankin
- Posts: 1082
- Joined: Fri Jul 14, 2017 8:45 pm
- Location: Spencerport, NY USA
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Re: 77 R100RS Rear MC Fluid Level Switch
The float drops with the drop in fluid, closing the circuit to turn on the bulb in the dash.
There is also a float in the front under the gas tank master cylinder. or should be one, it works the same way.
If the light has been out all this time, whomever removed the float may have bypassed the circuit to keep the light from coming on. I am guessing at all this, as I don't see where you took the float off your self.
A look at the BMW parts microfiche at Max BMW or one of the online BMW shops will tell you what parts are missing. Opps, I didn't look at my cap to see if it had a hole in the top. I am pretty sure it doesn't because a hole would allow moisture or water to get into the system and brake fluid and water don't mix.
Good luck with the repair, St.
Re: 77 R100RS Rear MC Fluid Level Switch
Now it makes sense, thank you for the assistance.
This bike was a barn build that had some work done to it but not finished prior to me taking it on.
Thinking about it the rear MC also had a missing seal and washer.
Much appreciate your assistance.
Regards Shane
PS this is her in current pull down.
Wollongong, Australia
Tooo many projects —— oh well
53 R25/3 Project
57 R26 Project
62 R50/2 Restored
64 R50/2 Project
67 R69S Original
71 R75/5 Original
77 R100RS Project