Review.IT, Remake.IT – BMW Z3 Battery Clamp Stud Bolt

Last night while I was in bed about to go to sleep, I had a thought.  The bolt I used to fix the battery clamp – I could machine the original bolt in the same manner.  In this way, instead of buying a replacement stud bolt, I can end up with a bolt that does the same thing, slightly shorter than the original.  I had fished out the end of the bolt that had broken off in the hole.


Here is the original bolt, with the broken piece at the end, and an identical bolt that I had used.  By the way, those bolts came from a barbecue that was dismantled.  I can turn down the original bolt and extend the thread so that I can put a nut on it to press down on the clamp.  Ok – put the original stud bolt into my lathe, turn it down to 6mm diameter.  Some of the corrosion came off – which appears to be battery acid corrosion.  Then I put my hand crank onto the lathe spindle to manually turn the bolt, while I use a M6 die to cut the thread.


Here it is with the clamp assembled.  Prior to installing it, I sprayed some white lithium grease onto the thread to protect it from corrosion and rust.  We just have to check that it is tight – from time to time.  This is my “review.IT” and “remake.IT” of the battery clamp stud bolt.

[NOTE] When working on the lathe, and on cars, it is quite remarkable that no matter how hard you try, you get grease on your hands.  I use a “Tuff Stuff” hand cleaner that is fantastic at removing grease and grime, and keeps my hands soft and smooth – as it is non-abrasive.  It has fine granulated polymer beads and has a fresh lime fragrance.

Retap.IT or Rethread.IT – BMW Z3 battery clamp mounting

A week or so ago, my son’s BMW Z3 had its battery replaced.  The car hadn’t been in use much – and we had charged the battery occasionally, but we must have left it too long, so the last time we tried charging, the battery charger indicated a battery failure.  Battery voltage was about 8V – much too low, hence a battery replacement was needed.  I got a good price from Onlinebatteries, with a great price on delivery – only $10.  What was even better was that the battery was delivered that afternoon, and the guy even helped with removing the old battery.  Here was the problem – he showed me that the battery clamp bolt would not loosen.  The bolt is about 7.5 inches long, and after some fiddling, it broke off in the hole.  Ok – no matter, at least the faulty battery can come out and within a short time, the new battery was installed.

Now, unless the battery is fastened properly – if the car goes over a bump, the battery might jump around – not good, and would invalidate the warranty.  That was a week or so ago.  This morning, I had a bit of time, so drove the Z3 down the road to our local mechanic.  He said that it is very fiddly to fix, and suggested that we just drill out the bolt, and either rethread it, or (like some people on the internet have done), put a bolt in through the bottom of the car, and have a nut on the other end.  Since I have most of the necessary tools, I decided to have a go at it.

Of course, the spare wheel – a space saver, is mounted under the car, so this needs to be released and dropped down.  I don’t want to drill the bolt, then go through the tyre.  I center punched the end of the bolt, which fortunately had snapped off flush with the mounting plate.  I drilled it out with a 3mm drill first – keeping the drill as vertical as possible.  Then followed up with a 4mm drill, and lastly a 5mm drive – which jammed in the hole.  Life was not meant to be easy – I hear that sometimes.  With a bit of wiggling and some WD40, the drill came loose, and this time I drilled, pushing gently and eventually went through.  It appears that I didn’t quite drill it centrally – or the hole wasn’t vertical, one or the other.  I poked around the hole, and the remainder of the bolt came loose, and I was able to push it out the bottom of the hole.  It was time to clean up the thread – or time to “” or ““.  The bolt was a Metric 6mm bolt, so I began tapping with a M6 starting tap, which I was able to do by hand.  Next was an intermediate tap, followed by a finishing tap. Great – I tried a handy M6 bolt and it threaded ok – just a bit looser than usual.

Since I didn’t have a replacement bolt on hand, I decided to put everything back in, after vacuuming the battery compartment, removing a lot of debris – that accumulated with time. A thought then occurred to me, the M6 bolt I had tried, it is similar to the original bolt, but without the flange that presses on the battery clamp.  I could put a nut in place and that would be the flange.  The bolt is much too short, but my 10mm nut driver would reach the bolt even with the battery in place.  So, I inserted the bolt with the clamp, and was able to tighten it so that the battery didn’t move.  It could well be serviceable for a time at least.


In the photo above, you can see the new battery and to the left (in the middle), the clamp with the improvised bolt to keep it fastened.  The plastic panel is still to be mounted, which covers all of the tail light wiring.   The plastic panel had been removed in order to get my drill to be able to drill vertically – as it was getting in the way.  I had carefully put all 9 assorted screws and bits and pieces into a plastic bag, and remembered in which order everything went back together.  All well and good!  Another successful repair.  I don’t think my son will be paying me for the 2 hours or so that I spent on this.

[Note] I was able to get the remainder of the bolt out, during the vacuuming. It showed me that the drill went in at quite an angle, yet I was holding the drill very much vertically. It turns out that the original bolt was tightened so much, that the mounting plate was warped to one side, so by drilling vertically, it went into the side of the hole.  Since only part of the thread is intact, this might explains the looseness – but it does tighten up, so we could leave it.  If in the future, I want to fix this properly – I would be best to use a thread repair kit, this is one where the hole is drilled out, and threaded then a M6 threaded insert is screwed in place.  This would then give a proper M6 hole for the bolt to go into.  Maybe that is a job for later, since I don’t have those repair kits on hand – but they are available locally.

Recondition.IT – Slide switch for crystal locked FM Radio

We have one of those three-channel crystal-locked FM Radio – commonly used for listening to the China Radio station 2CR and others.  It had been playing up at times and was unable to tune into any channel and was put aside a while ago.

It is a DP3T slide switch that is the problem.  Dual Pole 3 Position slide switch – with pin spacing at 2.5mm apart.  I was looking for alternatives and could find switches that have pins 2mm and 3mm apart, but not 2.5mm.  After some time, I was able to find a similar switch – a SK-23E01G, but would you know, I cannot find anyone who has stock of this switch.  I did find a couple of sites that do advertise this switch, but they require pre-ordering and have a minimum quantity of 1000 units – fantastic, except that I only need one piece.

My only option is to buy a new radio, or to “recondition.IT” – the switch that is.  The switch is used to select from one of three crystals that determine the frequency that the radio is tuned to.  I removed the switch from the pcb, then opened the housing.  It was immediately obvious that the switch contacts were worn and were oxidised.


There are two movable contacts – but the fixed contacts are not allowing good contact. To fix this, I used a 240 grit emery paper, to polish up the contacts, followed by 320 grit paper.


Now this looks better – at least the contact surfaces are shiny.  I reassembled the switch, then checked the switching resistance, and it was good.  Great, installed the switch, closed the radio, added four AA batteries, and voila – it was working.  Not bad for about 10 minutes work.

Repair.IT, Replace.IT – Paging PC not booting

On Saturday, a PC was delivered to me – an urgent repair job.  The PC has an 8-port serial card in it and is used to send messages to pagers – yes, pagers are still being used.  Anyway, the symptoms described are that it keeps rebooting – which very much sounds like hardware, but can be software.

On closer inspection, I noticed that a number of capacitors on the motherboard were bulging, a sure sign of over-temperature which causes the electrolyte inside to become pressurized almost to the point of opening the vents – some were open, you can see the dark marks on top of the can.  Anyway, replacing the capacitors is really not an option, hence a replacement motherboard is required.  I proceeded to check the motherboard model and found that it has a LGA775 processor.  Luckily there is still one motherboard available – a Gigabyte GA-G41M-Combo which will work, but it has DDR2 or DDR3 ram.  The old motherboard had only DDR ram – one 256MB module.  Anyway, as I would have to wait until Monday to obtain the parts needed, I thought I would power it up anyway.  It wouldn’t power up – or rather, it wouldn’t stay powered up.

I removed the power supply and connected my PSU Tester – it turns on then blinks off.  Ok – a power supply is also needed.  I connected my test power supply and proceeded to power up.  I can see the bios screen come up, but pressing Del on the keyboard doesn’t go into setup – strange.  Anyway, I see that it goes a little bit, then a beep and it resets again – so this is the symtom that the customer reported.  I proceeded to remove the heatsink, and processor – which was an Intel Celeron D 346 running at 3.06GHz.  It was then that I saw more capacitors that had failed, hiding under the heatsink.


Sharp eyes will see three on the right of the cpu socket, then a few more spread around the heatsink in the middle of the motherboard.  On Monday, I went out and picked up the new motherboard and a new 550W power supply.  Then I went out mid morning and disaster struck – my car broke down, overheating.  The car isn’t really part of this story, but suffice to say that 4.5 hrs later, my car has been towed to my local motor mechanic and I am home, having a cup of coffee and a sandwich.  Back to work – I proceeded to install the processor, using Arctic Silver 5 for the heatsink compound.  Don’t forget that I am reusing the cpu and heatsink, so have to clean all the old thermal compound off, then tint the cpu top and heatsink, then a smidgeon of Arctic Silver 5 – supposed to be 2.5 cubic millimeters or about a grain of rice.

Installed two pieces of 256MB DDR2 ram – double the original ram, will make it work better, but obviously it is only running a simple application so it isn’t necessary to have more memory.  Installed the power supply – connected up all the cables to the DVD-Rom, floppy drive and hard disk drive.  Power up – keyboard not working, USB mouse not working – ok, what gives?  Power off then back on – same thing.  It seems that the keyboard doesn’t work.  I have a spare PS/2 keyboard somewhere – ok, got it and tried again – good, my keyboard is working, but mouse isn’t.

Windows XP Professional – with a change of hardware will require reactivation.  Choose not to, because the network isn’t working.  I try to eject the dvd-rom, but nothing happens – it has failed too!  I downloaded the network driver from the Gigabyte website, since for some reason, the supplied driver cd won’t read on my laptop – then put the driver onto a usb flash disk, and used that to get the network driver installed.  Continue with driver installation – there are lots of drivers needed, eventually I got most of them done, then had to find the video driver, sound driver and last of all – the drivers for the Decision PCCOM PCI 8 Port serial card, which I can’t seem to find quickly.  No choice then but to get Windows to tell me which driver is wanted, then copy it out of the windows folder and point the hardware install to that location, and keep doing this for the other 8 files needed.  The drivers were already there, so I just had to find them and put them somewhere for windows to copy again.

So, a couple of hours later, everything is updated – Windows wants to install some XP updates – so agree to them, and eventually got it updated except for SP3 – I decided not to do this, because sometimes applications stop working when that is installed.  Oh, by the way, the floppy drive also had failed, but luckily the hard disk drive was still working.  How about that?  Power supply, motherboard, dvd-rom drive, floppy drive and keyboard had failed.  The USB mouse eventually worked after the drivers were installed – weird.

Final word – the Paging PC has been Repaired, with mostly everything in it Replaced – so that was “Repair.IT” and “Replace.IT“.

[Note] I think that the power supply was starting to fail – maybe introducing a lot of ripple onto the supply lines, which caused the capacitors to overheat – because they are trying to smooth the DC voltage.  Then eventually the power supply failed more such that the keyboard, dvd-rom and floppy drive was destroyed.  The USB mouse was still ok, so that only uses 5V and the drives use 12V – but why the keyboard – I can’t explain that.  So eventually the power supply failed completely and stopped turning on – at least for me.  The DDR ram might still work, but I need to find an old computer to test it.  When I get a bit of time, I may go through the exercise of replacing the failed capacitors and look at fixing the power supply, but at least the customer is happy now.