'77 Brake Fluid/Effectiveness Light

[Zulu]

On my early 77, I have the "Brake System Effectiveness Indicator", the small metal box that the brake lines run through, next to the master cyllinder, and the wire going to it. But then the wire splits off and goes nowhere. On my wiring diagram (came with the car 35 years ago), it says this is goes to the "Brake Fluid Level Indicator (If Fitted)". I understand that late-77s and up had this on the brake reservoir cap, but here's my problem: there's no ground wire, either in the car or on the wiring diagram. So where does this wire go? Was their a different level indicator on early 77s? Does anyone know? Please help.

Thanks
Zulu

[So Cal Mark]

the light on your car indicates a pressure failure in one half of the brake system. The valve has a pintle in it that moves off center when there is a pressure differential and that closes the circuit to ground, illuminating the warning light

[Zulu]

That's right. There's a brown wire that leads from the light inside to the "Effectiveness" sensor. On my car, that brown wire also leads to a connector that isn't hooked up. I have an original wiring diagram (came with the car) and it says that connector goes to the "Fluid Level Indicator".

I also know that late 77-85 cars had a fluid level indicator in the reservoir cap, which had a brown wire and a ground wire attached. I originally thought my mystery wire was meant for that, but then I realized that I don't have a ground lead, and the wiring diagram doesn't even show one! So now I'm totally confused as to what an early-1977 fluid level indicator is.

[vandor]

The wire should go to the negative side of the BRAKE light on your dash - the same one that illuminates if your handbrake it on.

[Zulu]

Csaba and Mark, I don't think I'm describing the issue well enough. Hopefully photos will help:


Here's a photo of my wires. The white arrows shows the path of the wire from the harness to the effectiveness sensor, and the red arrows show the path of the wire from the effectiveness sensor to another connector.


This is a photo of the wiring diagram. As you can see, the wire first goes to the effectiveness sensor, and then on to the fluid level indicator. That appears to be my mystery wire, but I've never seen a car with both the effectiveness sensor and the fluid level sensor, but my wiring diagram clearly shows this. But there's no ground wire for the level indicator like there is on later cars. How's that possible?

[vandor]

>As you can see, the wire first goes to the effectiveness sensor, and then on to the fluid level indicator.

I think they were on drugs when they drew that diagram...
I've never seen a Spider with both of those, it's either one or the other.

[Zulu]

In that case, I think I will wire up another ground and install the late model cap-with-sensor. Now I just need to find one that works.

[geert]

>
I think they were on drugs when they drew that diagram...
I've never seen a Spider with both of those, it's either one or the other.

In fact, the wiring diagram shows exactly what there is : a loose brown/white wire going nowhere.

If you connect it with a ground the red brake light should go on. If you put a switch ( fluid level controlled ) between it, it might even be usefull. ( or you can connect it to the switch on the clutch pedal to warn you with a red light when you're choosing the wrong pedal , or to warn you when the ABS system is activated ( optional ) .

Maybe they were on drugs, but they had great vision(s) )

groeten, Geert.

[Zulu]

The wiring diagram shows it going to component #41, not nowhere. #41 is labeled as the Brake Fluid Level Indicator on the bottom of the diagram.

I've wired it up with another ground and I'm going to put a late style cap and reservoir on it. Should be useful. More useful than my old "effectiveness" indicator anyway.

[westy64]

I found this post as I was trying to locate the brake effectiveness switch on my 76 (it appears on the wiring diagrams).
I was also wondering if I could replace my cap by a switch cap on the brake fluid tank.... and if these caps were standard size of specific to some tank models, and, last but not least, how to do this when you have two separate tanks ?

Is it better to have two tanks instead of one ?
Or is it the contrary ?
I guess there are pros and cons each solution, in case of a leak, you can always keep one tank, etc... ?

Is there an undisputed evolution on the late spiders ?
thanks for your help.
Jean

[JerryH]

The brake effectiveness sensor on my '76 was leaking, so I followed the advice of several people on the forum and replaced it with a late model reservoir and level sensing cap. I purchased a used single reservoir and cap from one of the forum members. I connected the wire that went to the BES to the cap and connected the other connection on the cap to ground. To make a cleaner installation, I replaced the drivers side front brake hardline (routing the line directly from the MC to the front left wheel). The rear brake line that went to the BES can reach the MC directly--it's tight, but if you route th line correctly you can get it to reach the MC. This seems to be a more reliable setup than the old system.

[westy64]

And what does this sensor look like ?
Where is it located ?

[JerryH]

Westy,
The sensor block is mounted on the wheel well right next to the MC. My post has a picture identifying the sensor:

http://www.fiatspider.com/f08/viewtopic.php?f=9&t=17595

-Jerry

[westy64]

Thank you Jerry.
I thought this was a "repartiteur" (to share the pressure between front and rear circuits- I don't know the english word for this).
But so far I have not found any connector to plug a wire on it.
I will look closer tomorrow.