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Need help: battery & parking brake switch


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Hi, I have a 2016 Golf R MK7. I have 3 questions I'm hoping someone here can help with...

 

- Was the stock battery an AGM and is AGM necessary? I ask as the battery was replaced in 2019 with a Bosch S5 non-AGM. Just replaced it again and current mechanic installed Interstate MTX-47/H5 AGM and said AGM was mandatory. If so, that means Mechanic #1 put the wrong battery in my car. Just trying to understand if it's mandatory, better, or what.

 

- When I replaced the battery, there was a lot of corrosion on the positive terminal only. Mechanic #2 said that was caused by non-AGM battery. I just got my car back and after 1 week battery is corroding again! He didn't replace corroded battery terminals and doesn't look like they even put anti-corrosion on as the terminal looks dry/flaky. Would a failure to properly clean up existing corrosion cause this kind of corrosion to re-occur, or does it point to another issue with the car?
 

- I'm getting a parking brake error/code, which occurred after the battery died and remained after the new one was installed. The brake works; I can feel and hear it engage/disengage, but the error remains and the switch itself doesn't light up when engaged. Mechanic says it's a hard code and that it needs a new parking brake switch. That doesn't make sense to me as the switch works, but I suppose something in the switch could be faulty causing the error? I've tried re-setting by holding switch up for 10 secs; nothing. I've started/re-started numerous times since getting it back and error code is still there.

 

Thanks for any and all input! 

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21 minutes ago, janjan said:

Hi, I have a 2016 Golf R MK7. I have 3 questions I'm hoping someone here can help with...

 

- Was the stock battery an AGM and is AGM necessary? I ask as the battery was replaced in 2019 with a Bosch S5 non-AGM. Just replaced it again and current mechanic installed Interstate MTX-47/H5 AGM and said AGM was mandatory. If so, that means Mechanic #1 put the wrong battery in my car. Just trying to understand if it's mandatory, better, or what.

 

- When I replaced the battery, there was a lot of corrosion on the positive terminal only. Mechanic #2 said that was caused by non-AGM battery. I just got my car back and after 1 week battery is corroding again! He didn't replace corroded battery terminals and doesn't look like they even put anti-corrosion on as the terminal looks dry/flaky. Would a failure to properly clean up existing corrosion cause this kind of corrosion to re-occur, or does it point to another issue with the car?
 

- I'm getting a parking brake error/code, which occurred after the battery died and remained after the new one was installed. The brake works; I can feel and hear it engage/disengage, but the error remains and the switch itself doesn't light up when engaged. Mechanic says it's a hard code and that it needs a new parking brake switch. That doesn't make sense to me as the switch works, but I suppose something in the switch could be faulty causing the error? I've tried re-setting by holding switch up for 10 secs; nothing. I've started/re-started numerous times since getting it back and error code is still there.

 

Thanks for any and all input! 

1. For vehicles with start stop systems my understanding is agm or efb fleece batteries. Agm best.

 

2. I've got a 2016 my r and mine has a halfords agm in it and it's never shown any corrosion on the terminals. I guess the older lead acid battery could have vented a bit and caused corrosion. Just guessing. I'd thoroughly clean terminals with a solvent or brake cleaner and refit.

 

3. Not sure about that error. What code is it showing? Is the mechanic saying its a fault reported because the led  indictator has failed on the switch? I don't have any experience of that fault but there will be a solution!! 

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2 hours ago, fastandy said:

1. For vehicles with start stop systems my understanding is agm or efb fleece batteries. Agm best.

 

2. I've got a 2016 my r and mine has a halfords agm in it and it's never shown any corrosion on the terminals. I guess the older lead acid battery could have vented a bit and caused corrosion. Just guessing. I'd thoroughly clean terminals with a solvent or brake cleaner and refit.

 

3. Not sure about that error. What code is it showing? Is the mechanic saying its a fault reported because the led  indictator has failed on the switch? I don't have any experience of that fault but there will be a solution!! 

Thanks for the input. I don't have a start/stop system. I had gotten conflicting info but just confirmed that lead acid was stock and is the current VW OEM recommendation for my car. 

Re: #3, the error on the dash is "Fault: Electrical parking brake." The mechanic said it was a "hard code" and that the switch needed to be replaced. I'm suspect of what he said as the issue was not reported to me when I picked up the car, which makes me question if they actually cleared the faults. (And also because they didn't fully clean the corrosion, and gave me incorrect info about need for an AGM.)

So I guess the question is...could the switch actually function but the LED indicator failure itself cause a fault? Or does the fact that the brake works mean the problem could not be the switch and that it's either a code, wiring, or other electrical issue?  

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A CTEK charger will help keep your battery in top condition if your R stands unused for long periods. 
Check out Tanya for both AGM  and EFB.    About £140 and under.  
The AA will fit for you for around  £255 and £230 respectively. 
 

I’ve done the searching recently.  My 19 plate R has yet to pass 10k miles and is still on the factory fit non AGM battery.    When I replace I’ll go AGM.  But you get a long guarantee with either.   
Hope you get sorted soon. 

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Thanks, I'll consider that for the future. And thanks for confirming that the stock battery was not an AGM - that was one of my questions.

 

Hopefully someone can share thoughts re: the parking switch / electrical  issue & potential cause of the corrosion happening with both the old and new battery.

 

Cheers,

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Thanks, I'll consider that for the future. And thanks for confirming that the stock battery was not an AGM - that was one of my questions.

 

Hopefully someone can share thoughts re: the parking switch / electrical  issue & potential cause of the corrosion happening with both the old and new battery.

 

Cheers,

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1 hour ago, janjan said:

Thanks, I'll consider that for the future. And thanks for confirming that the stock battery was not an AGM - that was one of my questions.

 

Hopefully someone can share thoughts re: the parking switch / electrical  issue & potential cause of the corrosion happening with both the old and new battery.

 

Cheers,

For non stop / start. But for my car with - stop / start option code PR-7L6 Battery PR-JOT is fitted and they are all EFB.

 

Not sure what market edit: region you are in?

 

The full vehicle scan for the fault on the EPB would help.

 

 

BAttery.jpg

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Corrosion on your battery terminals will be from your old failing battery and low voltage, disconnect the battery and give the terminals a good clean baking soda and warm water will neutralise it, dry them and apply some electrical grease- reinstall 

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  • 2 weeks later...
On 28/06/2024 at 02:27, DDave said:

Corrosion on your battery terminals will be from your old failing battery and low voltage, disconnect the battery and give the terminals a good clean baking soda and warm water will neutralise it, dry them and apply some electrical grease- reinstall 

Thanks, Dave...but why would it only be on the positive terminal? And why would it be re-occurring with the new batter (& old corrosion cleaned up?)

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.@janjan: Hi.

 

With @DDave's kind indulgence for butting-in on your discourse, maybe consider the following - please?

 

First an few words about "corrosion" and I may be entirely confusing the term as it's used by locals way up there on the sceptered isle!! I assume that you are referring to a whitish-blue frosting (let's both agree to call this "gunk") that is deposited around the battery terminal.

 .

If I'm correct (and please accept my apology if I'm not), there can be a couple of reasons for this - sometimes the gunk is caused by hydrogen gas or sometimes electrolyte leakage from the battery (often as a vapor, rather than as actual leaking fluid). Or it can also happen if the alternator overcharges the battery! If the reason is the latter cause, even a slight overcharging over a long period of time will produce noticeable build-up of gunk

 

It's not a surprising thing if you think about the extremely harsh environment around the copper based battery terminals. Copper generally resists oxidation (rusting) - but when it conducts electricity, copper sulfate is produced and this leads to battery terminal corrosion. Bluish gunk on the copper terminals can signify copper sulfate. The bad part of this effect is that copper sulfate does not conduct electricity well, and if sufficient build-up occurs on the battery terminals, electrical problems can result!

 

As for the matter of preventing "corrosion" (and IMO, of course) - I reckon that it all starts by CAREFUL cleaning the existing gunk on the battery terminal (if its NOT too corroded). I'm aware of a number of commercial products for this task, but I've found a baking-soda water-solution and an old toothbrush to work OK. Down here in the colonies (different climate to UK), I smear ordinary chassis grease, or Vaseline over the copper terminals to combat battery gunk.

 

And finally (and again IMO), it pays to check the car's rail voltage with a good voltmeter - emphasis on "good" because universally on this lonely blue planet - most (ALL?) voltmeters that mechanics use tell porkies!

 

With the engine revving and no electrical load, or Air con operating- if the charging voltage exceeds around 14.5 volts, maybe consider this cause. As I said, even slight overcharging by the alternator can cause battery terminal frosting over a long time! And don't bother taking advice from a mechanic that doesn't place the voltmeter leads DIRECTLY across the battery terminals - measuring battery rail volts anywhere else on the car is absolute nonsense!!

 

OK, as for the error-code - I'm not sure how to respond tactfully, but I respectfully suggest that it's NOT good practice to ignore error codes on a modern car like a mk7, unless you are absolutely certain that it's "ignor-able"! And when the error-code relates to a safety aspect of the car - a judgement like "ignor-able" probably requires extra consideration (no offense intended).

 

Of course I don't know what your mechanic meant be "a hard code" - but if he/she suggested replacing a part and if you trust this individual, maybe consider the advice?

 

Don

PS: As @fastandy suggests - post-up a SCAN report for this car so we can see the exact nature of this "hard code"

 

 

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11 hours ago, janjan said:

Thanks, Dave...but why would it only be on the positive terminal? And why would it be re-occurring with the new batter (& old corrosion cleaned up?)

The only other possible cause would be the alternator overcharging check it with a meter across the terminals with the engine running should be about 13/14v max

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When I did a quick search at the time of replying to this post originally, there were some reports of failure of the epb switch. so the garage could well be correct. a full fault code read would help clarify. Or if the garage is doing the job, let them do it - i.e. diagnose and repair - they will be responsible for the repair! 

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