P80 8638452 What causes a window master switch to fail?

[mrbrian200]

Current sensing/over current protection would be via external fuses and probably a PTC inside the window lift motors. The logic and relay is for the auto feature for certain.

[RickHaleParker]

Is that black box a relay?

Yes Part number V23076-A1001-C133 is a relay. It is not an obsolete part part, you can still get them for less then $2.00 each. Anybody that works on Automobiles knows relays are prone to fail.

[scot850]

Well I can now add that to the list for 'diagnostic' evaluation to find what actually fails and possible fixes. It would be good to have a proper fix than just using another probably as bad used one if it is of reasonable cost and easy to do.

Neil.

[RickHaleParker]

I started an investigation like Scott is doing a few year back because I suspected the master switch on my '98 C70 was defective. I ended it short because I determined the master switch was good. It was the window regulator that needed service.

Anyway the price of the C70 master switch is way higher then the master switch for the V70/S70 and harder to find. I took the top off a C70 master switch and a S70 master switch, the lower part of the two switches are the same. Leading me to the conclusion that I could save a bundle of money by mating the lower half of a V70/S70 master switch with the top half of a C70 master switch.

Still there is the "ended it short", I did not compare the electronics boards of the two. I know from experience that "wasting" some electronics components is often more economical for a manufacture then producing and managing two products. The odds that the two are electronically identical is very high but this needs to be confirmed.

[BEJinFbk]

Current sensing/over current protection would be via external fuses and probably a PTC inside the window lift motors. The logic and relay is for the auto feature for certain.

For overload protection, yes. The window and sunroof
systems share a bimetallic automatic circuit breaker in
position 11C/37. Not sure about PTC's, but but I'd agree
that like the lock motors, Volvo most likely has some in
the window motors as well.

I'm talking about current sensing as part of the auto-down
operation. Most automotive window automatic up/down
features sense current to determine the end of window
travel in the up or down position.

When you push the driver's window down button in a
P80 x70 and go past the momentary position, you hit
a second switch energizing the relay that continues
to provide power until the window hits bottom. As the
motor begins to consume significantly more current,
the increase is detected by the circuit and the relay
is de-energized.

[mrbrian200]

I typed too fast, the thoughts I was trying to convey were overheat/fire protection (PTC in the lift motor), and over current (external relay).
PTCs, at least the PPTC variety have been standard fare in lift motors for a very long time. I don't need confirmation: it would be a breach of 'standard safety design' for Volvo to omit it. A window switch that's 'stuck on', or being continually pressed by a child can overheat the lift motor and start a fire without the PTC. The external fuse really just protects against dead shorts.

These 'really old school' switches (not on a data network): The logic and relay don't come into play unless you push the button to the second click (for automatic). The relay bypasses power around the switch (that is no longer depressed), the logic turns off the relay at the appropriate time. If neither automatic or manual mode work then either the power circuit is broken, either in the switch or wiring, or the lift motor is bad.

If the lift motor and wiring were ruled out and you're having trouble determining why the switch stopped working, send it to me I'll sort it in short order.

[abscate]

When my switch went, I disassembled it, cleaned all the points on the copper switches.

A week later SWMBO complained it spit fire and smoke every once in a while, so I replaced with a new one.

[FLXC90]

I started an investigation like Scott is doing a few year back because I suspected the master switch on my '98 C70 was defective. I ended it short because I determined the master switch was good. It was the window regulator that needed service.

Anyway the price of the C70 master switch is way higher then the master switch for the V70/S70 and harder to find. I took the top off a C70 master switch and a S70 master switch, the lower part of the two switches are the same. Leading me to the conclusion that I could save a bundle of money by mating the lower half of a V70/S70 master switch with the top half of a C70 master switch.

Still there is the "ended it short", I did not compare the electronics boards of the two. I know from experience that "wasting" some electronics components is often more economical for a manufacture then producing and managing two products. The odds that the two are electronically identical is very high but this needs to be confirmed.

My investigative effort into this was by "swaptronics" I found a C70 switchpack, plugged it into POS70, and the windows did not operate because the ALL WINDOWS performed differently than the window lockout.

[FLXC90]

Arcing of contacts - little or no suppression . I’ve found some EBay/AliExpress units with better suppression/capacitors. The rare case of aftermarket better than OEM

I bought a $20 switch of amazon, plastic was wrong color and the LEDs are about three times as bright as other lights in the car. But it worked great-for about six months. Then the plastic shattered on the window inhibit button, sending a conical cap of plastic, and the tension spring into the ether.