Handbrake light remaining on

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itcaptainslow
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Handbrake light remaining on

Post by itcaptainslow »

I’ve got an MG ZS (so HHR, basically!) that I’m dealing with which has an issue - the handbrake light remains on intermittently, but usually permanently.

Speaking to the owner’s son, the car has had fitted a new fluid level sensor and handbrake lever position sensor in an attempt to cure the issue, with no success. The brake fluid level is fine.

Any suggestions for a “straight to the fault” diagnosis before I begin diagnosing the problem?
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GTiJohn
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Re: Handbrake light remaining on

Post by GTiJohn »

itcaptainslow wrote: Mon Dec 18, 2023 3:31 pm I’ve got an MG ZS (so HHR, basically!) that I’m dealing with which has an issue - the handbrake light remains on intermittently, but usually permanently.

Speaking to the owner’s son, the car has had fitted a new fluid level sensor and handbrake lever position sensor in an attempt to cure the issue, with no success. The brake fluid level is fine.

Any suggestions for a “straight to the fault” diagnosis before I begin diagnosing the problem?

If neither of the things being sensed are wrong and both 'sensors' are ok then the next thing to look at are the circuits, especially the earths.

Consulting a wiring diagram would be a good start - luckily, the 97-on circuit diagram is available to members in our document download area :cool
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itcaptainslow
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Re: Handbrake light remaining on

Post by itcaptainslow »

My next port of call! Thanks John.
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itcaptainslow
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Re: Handbrake light remaining on

Post by itcaptainslow »

Frustratingly, the document download system only allows you to view the document once before barking “Error - You’ve already downloaded this document” at me. I should have saved it to my iPad, but ho hum, I didn’t (not owning an HHR, I didn’t think to!).

Is there a way of resetting this? I need to find the earth point locations, now I’ve the appropriate wiring diagram.
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itcaptainslow
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Re: Handbrake light remaining on

Post by itcaptainslow »

A couple of initial wiring checks before I start having to pull trim apart to access the cabin earth…

Measured from the two plugs to the brake fluid level sensor, the circuit has continuity with the handbrake up, and no continuity with it down, indicating the handbrake switch is functioning. With the handbrake up, the circuit has 3.5 ohms resistance, and infinite with it down - again, looks logically correct to me.

The brake fluid sensor cap has infinite resistance, no matter what you do with the level sensor (the cap either immersed or out of the fluid, and displays 0.01v.

Initial thinking is the level sensor is at fault - any other thoughts/comments?
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GTiJohn
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Re: Handbrake light remaining on

Post by GTiJohn »

itcaptainslow wrote: Sat Dec 30, 2023 5:54 pm The brake fluid sensor cap has infinite resistance, no matter what you do with the level sensor (the cap either immersed or out of the fluid, and displays 0.01v.

Initial thinking is the level sensor is at fault - any other thoughts/comments?

My simple electrical knowledge suggests that it should do something different when it's not submerged in fluid, so I think that's the blighter.
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Re: Handbrake light remaining on

Post by 220 GSi turbo »

Seems likely to me. At first I was thinking that the sensor would 'make' the circuit when the fluid level drops, but after thinking about it I now think it would be set up to do the opposite so that there is a 'fail safe' in place.
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