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1984 DL, sunburned ruby red with 325K...
The failure light came on and no amount of stomping would reset it, yet both circuits have no leaks I can see. Against all recommendations I could find I decided to see if I could reset it through the switch hole.
Before loosening the switch (14mm 6pt) I used a continuity tester to verify it was still switched on - in the failure mode. Then, after removing the switch body, spring and pin this was staring at me via bifocals, flashlight and mirror:
Looked like a thing you'd unscrew with a standard screwdriver. But after screwing with it for a while and still seeing the same threads exposed, I decided to stick a hook in and pull it out:
Got all the switch parts out so I could now make out the shaft between the two actuator pistons, I guess are in the ends keeping the brake fluid where it belongs. No threads on that last part, but why it has a slot I have no idea! Cleaned up the switch and used a few Q-tips to clean the opening in the junction box. The probe shown above the switch parts in this photo is how I determined, with my continuity buzzer, the shaft was insulated.
I could see a dimple where the switch contact driven by spring pressure might have dented what looked like shrink sleeve over a steel rod:
Put it all back together, and like the probe predicted, no more brake failure light. Cliff is right -- I spent 10 minutes trying to start those nylon threads back into the junction block -- the spring fights you.
Here's my theory. When I changed a caliper a month ago I upset the balance temporarily. The piston moved, but the switch was dirty inside and took a month to make contact. The spring tension in the switch kept it stuck until I removed the switch, allowing the old piston springs to once again center it.
Either that, or that dimple is worn deeply enough to break through even though I could not with a sharp probe gently applied. Less likely I believe.
Hope I never have to replace this octopus.
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Art Benstein near Baltimore
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posted by
someone claiming to be Aunt Gertrude
on
Mon Sep 1 04:42 CST 2003 [ RELATED]
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I just pulled the wire off the octopus, and the dratted light went out!
I check the fluid every time I open the hood. Once in a while I shine a light down there to make sure that yet another one of Volvo's hazardous safety features isn't endangering me.
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Yes, Auntie, that's just how I got the car from the PO, 50K ago. Put the wire back on shortly after. You think I shoulda left things alone, then my daughter wouldn'ta had to mention it when I loaned it to her. But I'm not complaining. I'm enjoying these little Volvo-new-to-me oddities.
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Art Benstein near Baltimore
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I'm quite impressed at how you managed to do this while the junction was still in the car. They aren't easy to get at.
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1980 245 Canadian B21A with SU carb and M46 trans
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Trev, I put a jackstand under the left front jacking point just aft of the front control arm rear bushing. With the wheel removed, I could slide my head right underneath the block, working between it and the oil sump. But I couldn't see into the switch hole without a mirror or camera. Neck is kinda stiff today.
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Art Benstein near Baltimore
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Nice work Art.
You have confirmed my tentative theory about how it works, and I think you are right, disturbance of the braking circuit causes the piston to move and then get stuck. In theory it ought to be possible to shock it into recentralising without dismantling if you could lower the pressure temporarily in the other circuit. My suggestion was to push back the caliper pistons at one of the wheels solely on the other circuit (LH or RH back?) and then stamp the pedal.
Aren't you just glad though when the beast works so well for 99% of the time?
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Before beginning I'd read your post and everything I could find in Bentley, Haynes and Volvo manuals. The caliper I replaced a month ago was the LF, so I pulled the RF to retract the pistons. I got about 3/32 space between the caliper and rotor, pushed on the pedal (not really stomped). The booster still held vacuum so it fell quickly making up for the space. Then two thoughts (doh!) filtered their way through my thick skull: The master piston had a good chance of traveling where no piston had gone before, and (two) both circuits were represented in each front caliper - pretty equally too - so choosing the opposite caliper had no good basis.
So now I just cross my fingers hoping all the bleeding I've been doing may have kept the master from being trashed in that boneheaded move. But once the space was made up, I stomped a few times in an attempt to reset the indicator.
They might have made a switch with two contacts. They'd be normally closed, so the switch would be tested as part of the warning lamp test. With two contacts, the circuit with low pressure could be identified when it happened.
I thank you for your post even if I did ignore some of your advice. The replacement of that particular octopus looks far more daunting -- I envision buying a lot of brake line given my luck and rust environment.
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Art Benstein near Baltimore
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Good work, Art, ..
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john,,1985, 245:GLTi 246k mi..so.california
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John, I hope what I've learned and shared will help, but only time will tell.
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Art Benstein near Baltimore
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I hope it keeps working...personally, I replace these octopi whenever they go out..cheaper ($40) than rearranging my face around the steering wheel in my 83 245.BTW, I got one on Ebay for $11. Brand new.
buena suerte,,
el Raidman
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Raidman,
I'm scared of the prospect of loosening eight brake lines that look perfectly fine to me where they are. If that octopus was leaking past the switch (or should I say when) I'll get a new one and perhaps I'd better be prepared to get some replacement lines too. You make it sound like a walk in the park for safety (smile)! Guess I'll have to learn what you've learned someday...
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Art Benstein near Baltimore
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I just took the brake lines off of one that looked really rusty and I was shocked to find that they came off pretty easy. The block on my 89 has the factory undercoating all over it and you could almost undo its lines without a wrench. So coating it with something like Fluid Film helps
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Hmmm. I'd expect to hear that from someone in West Texas, but Jessie, I expected you to say get ready to replace 8 brake lines, judging by your other experiences with rust. That is encouraging. I suppose there's a lot of bleeding afterward. Fluid Film? Haven't seen that down here -- kinda makes me think of Liquid Crystals. Thanks!
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Art Benstein near Baltimore
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posted by
someone claiming to be Niel
on
Sat Aug 30 20:51 CST 2003 [ RELATED]
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No fighting if you've got right hand drive! The placement of things make more sense on RHD.
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Art, Something does not look right, I think I remember seeing a cut away drawing of this block.
It looks like your shaft is off center, I think the center of the shaft has a detent or valley that the contact pin rides in.
When the shaft shifts, the larger portion forces the pin up and makes contact with connector with the wire lead and completes the circuit.
I think thats the way it works. Maybe someone else will have some insight.
I can't explain your electrical findings.
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Bruce S. near D.C.
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What we saw in Art's pictures is OK. I have had one of those puppies apart. It is simply a piston with an insulated sleeve at it's center, no detent. There is strong spring at each end, keeps the piston centered.
The piston when moved can stick due to accumulated crud or corrossion. I should think that a gentle tapping with a hammer might recenter it.
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David Hunter
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Bruce, I swear I'd seen one too. Went through every manual I have, Bentley, Haynes and Volvo, but somehow missed it. If you can think of where you saw it, please let me know.
On the switch contact arrangement, on mine I found the spring, contact pin and terminal connection to be electrically one, such that the brass contact would always be connected to the warning light. Can't explain the slot in the inward insulator piece though -- the one I thought would need a screwdriver to remove.
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Art Benstein near Baltimore
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Art, there is a good photo (exploded view) in the "Image Library" on the 4th page, currently (link below). But I'm not smart enought to copy it here. Seems like there *was* a "return to reply form" or equivalent, the one time I used the IL.
Also, I think Cliff's idea about reducing/relieving pressure might work IF:
1) You could determine which way the slide/piston needed to move,
and
2) You could relate that to a Left or Right REAR brake, as Cliff said. (maybe even open the bleeder, with hose and helper??)
A different Bruce,
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Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified--and going to be crushed unless...)
New 144 from '67 to '78
Used '62 122 from '63 to '67
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test image transfer
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Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified--and going to be crushed unless...)
New 144 from '67 to '78
Used '62 122 from '63 to '67
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Bruce,
Now I know where I'd seen this before! I wonder why the archive search didn't include Randy's work here.
I'm going to attempt to copy it here by highlighting the text in the HTML box that shows the image location in the gallery, copying it ctrl-C and then pasting it here ctrl-V. Here goes. (looks like it is root referenced)
Not to be greedy, but I was interested in seeing the caliber of the end springs that are supposed to reset this.
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Art Benstein near Baltimore
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Hi. I'm happy for your success at clearing up the problem, but I'm really writing just to compliment you on your close-up (i.e, macro-) photography. Nice work -- what kind of camera did you use (digital?).
Best regards, and happy holiday.
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I appreciate the compliment. It can be a challenge to maneuver a camera into those spaces, for example between the left control arm and steering shaft. Mine is rather large too, as cameras go these days - a Nikon CP995. The difficult part was getting the flash into the hole, because the camera mounted flash is purposely far from the lens to reduce red-eye, I had to try to hold a flashlight and a still camera giving me a sore neck lying in the gravel trying to read the monitor in my bifocals. But your compliments and saving stress on my poor memory makes it all worthwhile.
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Art Benstein near Baltimore
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