850 ABS-unit failure in hot weather after first resoldering?

Last fall (on the northern hemisphere) I have done the traditional resoldering
job on the contatcs of my 850TDI 1997 ABS-unit. No failures after that during
the cold period. Now summer is approaching and lately some days when outside
temp is about 25 centigrade or higher the ABS and TRACS light go on again. When
turning off the engine and restarting, usually the lights disappear again. In
the morning when temp is still cool around 10 degrees centigrade, there is never
a problem during my 80 km trip to work.

I suppose that my soldering was still not good enough and during high
temperatures the different expansion rates of the materials cause again bad
contact. I did not glue the lid of the unit back with plastic mass as suggested,
but attached it with several layers of strong adhesive tape. It should be
dusttight at that place.

So I plan either to resolder it myself or send it somewhere to have it
resoldered.

Any other suggestion what might be the cause for the heat-failure of the
ABS-unit?

Franz47

 

Hi Franz,

I did the ABS module repair to my 1996 - 850 about 2 years ago and have not
had any problems since. The two large pins were the source of the problem, I
couldn't see any cracks in the soldering of the small pins. I have worked
in electronics for many years so a reliable repair did not present a
problem.

Your symptoms still sound like a broken solder joint. The cable hanging off
the two big pins can put quite a large mechanical load on them if the cable
vibrates at all, and they may have broken again if you didn't do a good job
first time around.

As you didn't glue the lid back on (getting the lid off was is the hardest
part of the repair), and the unit is reasonably easy to remove from the car,
I suggest you have another look at it. Inspect the two big pins carefully
with a magnifying lens and a strong light before you try to resolder to see
if your previous soldering has failed. As the board has plated through
holes, use a large enough soldering iron (60 watts or so) and take enough
time to properly melt the solder right through the plated hole. If you
haven't the expertise or tools, you should try to find someone who can do it
for you. Make sure you remove the conformal coating from around the pins
before you start (carefully scrape it off), and use the proper rosin cored
(or similar) solder sold for electronics work. It wouldn't hurt to re-seal
your work after you finish. I like nail polish (I steal it from my wife).
Clean off any excess flux using alcohol or similar first.

Temperature cycling can effect broken soldered joints just as you describe,
but the failure will eventually become "all the time".

I you do repair it successfully, I suggest you re-seal it properly after
you're happy with it. Use a neutral-cure silicone sealer (read the label).
Ordinary silicone sealers contain acetic acid which is not good for
electronic circuits.
Good luck

Barry

 

Franz

Just a footnote to your question and maybe related?

I had the same warning lights on my car (1997 850R) and it turned out to be
the ignition switch contacts had worn. A new switch cured the problem. Quite
an easy fix but you do need some of those new fangled 'Torx' gizmos to get
the screws out.

ttfn.....Alistair

 

I have done some home soldering which I learned from my father who was a hobby
electronic fan until the advent of transistors.

I think I did not dare to use a 60 W iron, it was probably a 15 W iron. I was
afraid to cause damage to the components by excessive heat.

I did it with a little Dremel - type tool, was actually not very difficult.

Did you take any precautions to prevent excess heat flow to the components? Or
is it that the two big pins are the DC supply lines and there is no other
connection than to the plug outside the box? Maybe I really give the job to an
electronic shop, who has the proper equipment. Still cheaper than a refurbished
unit or one of the repair services offered.

Good idea. I did not reseal it last fall.

I do already have a product Hylomar at home suggested by experts. I did not yet
glue the box together since I wanted to see whether the soldering lasts -
apparently not.
I will do the job within the next weeks when I have time..

Regards
Franz47

 

Thanks for the input. Sounds definitely more expensive than the soldering job,
which helped last time - unfortunately only for some time. I have bought a set
of those Torx-screwdrivers and the one nut necessary for removing the ABS-unit.
Also elsewhere on the car there seems to be exclusively Torx-screws.
Franz47

 

http://img503.imageshack.us/img503/5367/usualsuspectgh3.jpg

Do you mean the two large pins on the lower right corner?
Franz47

 

Hi Franz

The two pins in your small circle are the two that needed re-soldering on my
unit. I did resolder a couple of other suspect joints on the "long
connector" but the two pins on the separate connector were definitely
cracked.

I had no worries about this type of work as the last 45 years of my working
life (yes, I'm and oldie) has been in electronics. This is what I'm
familiar with.

As you do not have any electronic components really close to these pins,
overheating semiconductor parts is not a problem, and quite a large amount
of heat is needed to successsfully resolder them, due to the size of the
pins. I'm talking about leaving a 60watt iron in contact with each pin for
up to 5 or so seconds (depending on the iron), and making sure the solder
melts on both sides of the PCB.

Have a good look at your previous work before you touch it, to make sure it
needs reworking. And as I said before, if you're not happy to do the work
yourself, try and find someone else who can for you. It's not something you
want to write off if you can help it :-(

Regards
Barry

 

All of the ones that are circled are likely suspects. Notice the big
heavy pins and the large ground plains surrounding them. It's difficult
to wave solder a board that has a mixture of fine and heavy stuff like
that, hot enough to really flow well on big heavy connections is hot
enough to fry small sensitive parts.

 

When my ABS played up it was the same ,turn it off start again and it would
be ok most times .When it refused to work correctly I went through every
thing and found the contacts through the fender up on top of the fender were
dirty though not to the eye .Once cleaned and put together with some
vasoline they are working well .My car was shuddering and pulling to one
side when stopping now its fine after a clean up .check all contacts ,clean
and make sure you clean the sensors at the wheel .

 

Make sure you suck up(the tool is cheap to buy) the old solder and clean up
your work before you resolder .Hair line crack in old solder can mess up the
job start fresh . Still think you ought check the connections every where
you can ,as dirty contacts tricked me .

 

Sucking up the old solder does hurt, but usually it's not really
necessary unless it's really oxidized or contaminated. You just have to
make sure you get the joint hot enough that the solder flows together
completely.

 

Many people gave me good advice-thanks.

I will have the unit resoldered at a commercial electronic repair shop.

I started to remove the unit last week, using the Torx-nut I have used last
year. I vagely remember that the Torx-heads of the screws were somwhow worn
already last year so I had already bought screws of same dimensions but with an
Inbus-head. When I too quickly started to remove the unit, I very probably
maltreated the head of one screw now, unfortunately the worst accessible lower
closer to the driver. Next step is that I have borrowed another nut set from my
mechanic. Unfortunately there does not seem to be enough space to apply some
hammering on the nut to fit to the Torx-head. Cross your fingers I will get the
screw opened!

In case I cannot open the screw in place, I cannot see another way than removing
the ABS-pump-unit including the electronic unit and then with the screw
accessible on a work bench open it somehow.

Today I called a Volvo shop to ask whether the screws can be bought in case the
ones I bought wouldn´t fit - the screws alone cannot be bought for my 850 model
1997 with TDI engine and automatic tranny. They advised me to try at a Volvo
junkyard - will see whether it will become necessary and I expect the
screws´heads to be worn there, too. Until 1995 the units´ screws can be still
purchased. As much as I could see from the VADIS pictures, the older units and
screws were completely different from mine, so hoping to find a longer screw
there and shorten it, seems vane.

Any other idea?

Franz47

 

You shouldn't suck up the old solder, it will burn your lips ;>

Use a solder sucker, it is a soldering iron with a suction bulb on it.
There is also solder wick which is a stranded copper braid with rosin
solder flux in it.

It is best to use an experienced technician to do soldering since cold
joints are difficult to avoid unless you have the right equipment and
some experience. Cold solder joints look OK but do not make a good
metallurgical contact.

 

Both are silly places to look for screws. Try a local hardware store if
you have one, not to be confused with a home center. If that fails, call
up Tacoma Screw, Fastenal, McMaster-Carr, etc and they can almost
certainly help you out. The screw ought to be a standard metric size.

 

If you still need the screws I will locate some @ work on Thursday &
place in a safe place & if you can not locate them where you are then
get back to me & i will send what I have to you
Glenn K
Volvo Certified Technician 2008
ASE certified Technician 2008

 

On 6/2/2009 6:15 AM, franz47 wrote:

Hi Glenn

Thanks for the offer to help. I found some screws at home with probably the same
length and diameter with an Inbus head I have bought last year as a future
replacement, when I had seen that the Torx heads were worn. I haven´t been
successful finding the screws yet. When the originals are out and the unit at
the electronic repair shop I will see whether my screws fit or not. In case not
I will return to your offer. If your e-mail address is correct, I will contatct
you through it.
Regards
Franz47

 

The E-Mail Address is not correct to contact me get in touch with me
through this group & will set up a way for us to handle the offer

 

Before you resolder check a site that explains how to solder correctly
,enough heat with out ruining the solder .It should look shiney when
finished .If it looks dull its most likely incorrect.Yes you might burn your
lips but then would you feel it any way?

 

Dull or shinny is not a deal breaker. The trick is that the solder must
WET both surfaces it is soldering together. When the solder doesn't wet
one surface, you get what is called a cold solder joint. It is a
mechanical joint but not a metallurgical joint like you get when the
solder wets a surface. Most cold joints have a nice shinny surface.
The factors that determine success and failure include:

Tools:

The right size solder tip for the job and the right surface on the tip
for the solder you are using. Don't use a 1000 watt gun when you need a
35 watt iron.

The right solder for the metals you are joining. Use the right amount
of tin.

The right flux for the solder and the metals and the size job you have.
It must be a non-corrosive flux.

The right tip temperature for the job. Too hot or too cold won't work.

The right heat sinking for parts that need to be protected from excess
heat. Soldering one thing can make something else fail.


Technique:

The knowledge to know how to prepare the surfaces.

The knowledge to know how to prepare the tip on the soldering iron.

The knowledge to know where to apply the heat.

The knowledge of how much solder to apply and where to apply it.

The knowledge to know when both surfaces have been wetted properly.


It is not a trivial thing. Many people are lucky and get by. I few
people know what they are doing and get it right every time. I worked
for AT&T Bell Labs and our technicians could tell when an engineer did a
solder job. I was an engineer and usually got it right. The
technicians got it right every time.

 

I had the unit repaired now at one of the very few still existing electronic
repair shops in a city of 1,6 millions for a reasonably price. The guy said it
was quite a job to clean and resolder the indicated connections but it seems to
be ok now. After installing it and turning on the ignition, the ABS- and
TRACS-lights went out quite quickly. After dysfunction before the repair often
the lights stayed on until having driven about 10-20 meters, first then they
went out. Tempomat and speedometer work. I have not hat a chance to test the
ABS-function here in the city but will test tomorrow in the countryside on a
gravel road but if the unit survived my soldering work last year, it must have
survived the work of a craftsman. If that works I will take it out and seal the
surface of the circuit and the box. I was not successful to find definitely
acetateless clear high temperature silicone so I will use a spray sold in an
electronics market meant to cover circuits with a film against moistness etc.
For sealing the lid I have something appropriate. Hopefully this will be the
last work on the unit for ever!!
Franz47