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p80 Headlight wipers internals

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

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s70dean
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Joined: Fri Aug 26, 2016 4:21 am
Year and Model: 1999 awd 1998 t5m
Location: Cambridge

Volvo Repair Database p80 Headlight wipers internals

Post by s70dean »

I know the headlight wipers are pretty much useless on these cars,,,or any car for that matter. And I know most of you have just deleted them and life is good.
But I'd like mine to work as they should even if it's just for giggles.
Now my left front wiper works fine. It's the right one that's giving me troubles. It only seems to stay on long enough to get half way at a time on any given command and eventually gets to the home position.
Now I've went to the scrap yard to grab a couple cadavers to dissect and have a few questions. I can get the doner wipers assemblies to work but they stay on continuous and don't cycle like they should. What's that little square metal block between the copper leads? What tells the wiper assembly to shut off at home after the wipe command is given?
Just curious if anyone has solved these great mysteries of the s70 wipers and can lend some knowledge to amuse the crowd peops that want to know.
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DeathRex
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Re: Headlight wipers

Post by DeathRex »

http://www.matthewsvolvosite.com/forums ... hp?t=40352

The little square metal block is a PTC thermistor. A PTC thermistor's resistance rises as it warms up (now a days you would use a resettable fuse). The PTC's job is to decrease the current if the wiper gets stuck, or when it hits home.
If it only works for a short time, if might be drawing too much current and the PTC is increasing in resistance. The motor and gears need a lot of lube, make sure the grease is clean and not drying out. The motor should have an almost airtight seal.

If your wiper doesn't stop at home, it stops pointing up, or anywhere else, you can adjust it.
There is a red gear (I guess also could be a cam) that rotates the wipers and does the timing too. To adjust, first put the wiper on and see where it stops, then pull out the red gear a bit and turn it about 1/12 a turn or so, and see where the wiper stops. Once you get it close, install on the vehicle and check it. If it stops too early, the small white gear might go too far and the wiper will just keep going and never stop. Just back it up one tooth and check again, or move the wiper down so it hits and check. It the timing it still off, the wiper might go down before going back up and you'll have to readjust the timing.

There are 3 wires in the harness, one is used to start the wiper, one is used to run the wiper and the last is ground. If you put power to the motor start wire, the wiper will run continuously. I seem to remember that the motor run wire has a diode in series.
If you have ever timed a VCR from the 80s or 90s, or taking a teletype apart and reassembled you should have no problem.


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abscate
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Re: Headlight wipers

Post by abscate »

Nice...except you will have to add VCR to the acronym dictionary

:-)

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