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Do it yourself ABS module repair.

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.
1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Do it yourself ABS module repair.

Postby Ozark Lee » 07 Oct 2007, 22:56

The latest addition, a 1996 850 sedan, came home with the Tracs light on and the ABS light is burned out. It makes me think it had been that way for a while. For grins I decided to try a do it yourself fix and it apparently worked.

The obvious first step is to find an E-5 Torx socket. If you have an O’Reilly Auto Parts in your area they can get you one quickly. Virtually no store stocks them but they do stock them in the warehouses. I ordered one by phone at 9:00 AM and it was at the nearest store by 1:30 PM, US $2.99 plus tax. It is a Lisle part number 26770.

DSC02265.JPG


The process at the car begins with removing fuse number 14 from the fuse box and then disconnecting the power connector and the signal connector from the ABS module. It is easiest to remove the signal connector first which is done by depressing the catch and lifting the connector shell straight up, The connector hood hinges and this releases the connector. If the car is to be driven while the module is being repaired it would likely be a good idea to wrap the connectors in a Baggy and to secure the connectors away from things that get hot.

Here are the release points.

Underhood with labels.jpg


The next step is to remove the four Torx bolts that secure the module to the pump/modulator assembly. In my case with an normally aspirated engine I found that removing the air heater pipe from the airbox gave me much more room. Three of the four bolts come out easily but the fourth bolt, lower front, is largely blocked by the throttle cable. I found that putting the ratchet below the throttle cable worked the best.

Once the torx bolts are removed and set aside the module is removed by dropping it an inch or so to clear the solenoid plungers.

Here is the removed module.


DSC02268.JPG



DSC02267.JPG



The next step is the hard step. Clearly they don’t want you to open the box. It has the press on retainers around the posts and the entire box has a silicone seal. The press on retainers were very corroded and rusted around the posts and after futzing with them for 20 minutes or so I just fired up the Dremel tool with a cutoff wheel and sliced through each of them and removed them. I then tried to release the silicone seal by using a small screwdriver and raking it vertically between the lid and the base, pulling the silicone out from between the top and the bottom housings. I was trying very hard to keep all of the plastic intact but I was unable to do so. In the end I might have been better off scoring the whole outer lip of the lower housing away with the Dremel tool from the start. After much scraping, prising, and breaking of the lower lip I was able to remove the top off of the module.

Here is a picture of the attempts to pull the sealant away from the respective halves of the cases.

DSC02269.JPG


Once inside, the circuit board is revealed. The circuit board is covered with a clear silicone like membrane over its entirety. After much research I have learned that the failure point on the modules is the solder joints on the connectors, particularly the power connector. In order to see and assess the solder joints it is necessary to remove the protective membrane from the circuit board in the areas that you want to solder. This is easily accomplished by slipping the tip of a knife under the membrane at the edge of the circuit board and lifting it off.

Here are some pictures of the PC board with the membrane partially removed.

DSC02270.JPG


DSC02271.JPG


DSC02272.JPG


The solder joints that usually go bad are circled here.

Usual Suspect.jpg


From here it is a matter of re-soldering the joints. The power pins are obviously solid as they act as a large heat sink. I think this is the root problem with the modules from the factory. The pins themselves need to be heated quite a bit in order to get the solder to flow properly between the pins and the pad on the PC board. I used a 40 Watt soldering iron and laid on the pin for a good couple of minutes each in order to preheat the pins and then added solder. I left the iron in place until the solder flowed. I was somewhat worried about keeping that much heat on the pins and possibly damaging the circuit board traces but the pins are a large enough heat sink that the board can take a lot.

Once the joints are soldered it is a matter of resealing both the circuit board and the case. I had a tube of black, pure silicone, sealer and I gobbed a bunch of it on the PC board where I had removed the original protective membrane. I then put a generous bead around the edge of the lower housing and pressed the two together. More silicone than I used would have made the job look prettier but it certainly looks well sealed from the elements.

DSC02274.JPG


From here it is a matter of allowing the silicone to dry and re-installing the module.

In my case I fired up the car and the Tracs light came back on but it went out immediately after I took off up the street. I think that, if I had an operating ABS light, it would have gone out as well.

While I’m sure Victor and the other rebuilders have better tricks, this was something I could do myself and paying for half of the 140k timing belt job - slated for next week - in savings doesn’t hurt either.

…Lee
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Last edited by Ozark Lee on 21 Oct 2008, 20:28, edited 2 times in total.
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Postby MadeInJapan » 08 Oct 2007, 02:25

Good job Lee...I'm pinning this one!
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Postby ColonelCash » 21 Oct 2007, 23:56

I'm trying to determine if my ABS module on my 99 S70 T5 has crapped out on me or not. Here are the symptoms:

- Yellow TRACS Light ON (constantly) - triangle with car and fish-tail like arrows from back?
- Red BRAKE Light & Orange ABS Light come on at times.
- When BRAKE and ABS light come on, my speedomoter drops to ZERO and the mileage turns into '--------'.

When the BRAKE and ABS lights turn off, the spedomoter and odometer pick back up and work for a bit. Car seems to pull a bit when the BRAKE and ABS lights engage, but it could just be me.

This started to happen today when I was driving back to Nashville, TN from Lexington, KY.

Thanks!
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Postby MadeInJapan » 22 Oct 2007, 00:34

Sounds like the module to me.
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'04 V70 2.5T Red/Taupe Some Upgrades Mobil-1
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Postby Rodrigo Amaral » 23 Dec 2007, 12:13

yes, it seems to be the ABS module.
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Postby bigric » 17 Feb 2008, 01:26

Did this today. Besides opening up the box (I have no idea how they do it without cracking it just a little) it was a snap. I used a 5/32" socket to remove the four screws with no problems at all. Thanks for the great writeup!
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Postby fushionEdge » 18 Feb 2008, 05:01

So you just apply solder to all the joints in the circle?
The joints are the circles right?
Is that bad one visable as being bad?

Suggestible for a soldering newb like me, or better to send it out to Vic?
Thanks!
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Postby MadeInJapan » 18 Feb 2008, 05:08

If you've never soldered, I would send it out, but that's just me.
'98 S70 T5 Emrld Grn Met/Beige Tons of Upgrades Mobil-1
'04 V70 2.5T Red/Taupe Some Upgrades Mobil-1
94 850 Sedan NA Drk Blue/Tan
'00 V40 Purple/Grey Mobil-1
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Postby chuckcintron » 18 Feb 2008, 21:28

Is that all this repair ends up being -- reflowing some cold solder joints?

What about all that talk from the repair guys about "we use replacement components that exceed the original specs, etc." There's nothing really being replaced, save for some nasty old solder (?)

-Chuck
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Postby Ozark Lee » 18 Feb 2008, 21:52

So you just apply solder to all the joints in the circle?
The joints are the circles right?
Is that bad one visable as being bad?


More or less that is it. If you have good eyes (I don't) you can see the cracks in the joints. The smaller joints take very little heat and very little solder. The power connectors take a ton of heat to get the solder flowing. I think that was the original problem when the modules were made, the pins should have been preheated before the circuit board was flow soldered.

You will know for sure that it will work right if you Victor or one of the other guys to fix it but my repair has held up perfectly.

...Lee
'94 850 N/A
'96 850 N/A
'96 Platinum Edition Turbo
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Postby lewismug » 23 Feb 2008, 17:48

Lee, I just want to let you know that your write-up on this gave me the confidence to give this a shot. I have been dragging me feet about this problem trying to decide what to do. I cracked open the case last night with my dremel and fired up the soldering iron. I could clearly see several broken solder joints. I went ahead and flowed all of them that were broken, along with all of the others you had circled. My ABS light is now off, but each time I get above 20 mph, my brake light illuminates. It didn't do this before the ABS repair, so I'm guessing I may have missed a few joints. Has anyone else had this problem? If so, how did you get it to stop? Getting back into the unit will be much easier this time around, since I used black silicone to button it up. Any clue as to which pins it could be? I couldn't see any more that were broken.
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Postby JRL » 23 Feb 2008, 18:13

BRAKE light, not ABS?
Have you checked the fluid level lately
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Postby lewismug » 23 Feb 2008, 18:41

Now, ya see! That's the reason I value this board so much. The ones that think of the MOST obvious reason a brake light would be on. I am an idiot. Thanks for waking up my brain today JRL.
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Do it yourself abs modulator repair.

Postby TomPaol » 06 Apr 2008, 14:53

I got excited to attempt this repair and am at a stand still on getting the last screw out of the modulator to remove it. I have tried every angle and tool I can think of but can't seem to find the room to turn the socket. I even went down to a 6 degree wratchet. How did you guys do this. I have removed the air cleaner as well.

I would appreciate any suggestions.
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