Hi Everyone,

I've been ignoring my 240's minor but accumulating problems, but here is one I have been trying to solve for 3 years now: the rear defrost rocker switch melts, then becomes stuck, then eventually no longer works.

Could be a poor design? Could be 22 year old plastic just not up to the task? Could be too much current (I had a replacement rear window installed 3 years ago, as well)? Or is there a cutoff somewhere that could be broken, letting it overheat?

I have just melted my second (junkyard scavenged) rocker switch. I don't mind just installing a toggle switch, but I can't find any rated for high-amps DC. All I can find are very low amp DC switches (3A max), and I am guessing that this thing is pulling much more than that, at least at times. How bad an idea would it be to install a 20A 120VAC rated toggle switch?

Thanks all,
-Kevin

Do you get any de-misting at all?

Sounds like somewhere in the rear window replacement the wiring got crossed up and/or shorted. But not an immediate blows-the-fuse-now short.

Are you in a 242/4 or 245? Wiring for the 245 rear demist gets involved in the cargo door hinges. Not so in the 242/4

From the wiring diagram, looks like the rear demist runs off Fuse #11, along with the overdrive (man and auto). So, if the fuse blew you would know it is (1) no rear demist, or (2) no overdrive - if you were in overdrive at the time.

I would recommend not replacing the switch with the 125vac one, since it seems that the switch failing is a weakest-point failure and moving that point to another part of the circuit may make harder-to-find damage.

In the wiriing diagram, the rear window gronds on the right side. The feed wire is yellow, and runs along under the left side in a large harness you will find under the carpet. It goes to a connector, 3-wire, above the driver's left toe. The wires in that connector are yellow, red, and brown. the other wires feed the rear marker lights.

That yellow wire ought to be getting pretty warm if the problem is in the rear window circuit. It could be elsewhere, I suppose.

Good Luck,

Bob

:>)












--
240s: 1986 244GL, 1988 244GL, 5 other240s and one lonely FIAT 850.

Hi Bob,

I've had two 83s. Both had a lighted momentary rocker plus timing relay that handled the current for the rear defroster, unlike the old, plain rocker on the '79. Were these premium options or something?
--
Art Benstein near Baltimore Crrrrazy Ray's!

I haven't seen the momentary rocker. (This is a 240DL, btw, not a 245) The original one was a lighted rocker, but not momentary. The light in the bottom half of the rocker was this kind of clever setup with only one ground (I think) terminal, and the second terminal was a little metal tab hidden inside the plastic switch itself.

The second one I melted (from an '85, I think) was a non-momentary-rocker type too, with a light, but had two terminals instead of the prone-to-melting little metal tab inside. Thus I have no light hooked up, and can't even tell if it is on or not, although I think it is not.

The overdrive is fine, though, so its not the fuse. I'll take a look at the wiring to see if there is a timer or current limiter somewhere.

My new best theory now is that the new back window has larger (and so lower resistance) demister wires painted on than the original.

Thanks,
Kevin

Art and I have had this conversation and it seems that Volvo made the change during the 83 model year. Dtr's 240DL was built in 10/83 and has the on/off rocker that carries all the current for the demister - no relay. Still OK. But I prowled the yards and found an 84 and an 86 and pulled the momentary contact rockers (with the same demister logo on it) and the associated timer relays. I actually hooked the relays up and bench tested - both switched off after 13 minutes. I plan to retrofit one to my son's 81 and the other to the 83.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and numerous old motorcycles)

And I thought _you_ were the guy with CRS...
--
Art Benstein near Baltimore

New back window? Deja vu from last week where son's car blew the fuses with aftermarket window replacement? That was a sedan-- I'm assuming when you say it is a 240DL not a 245 you mean a sedan not a wagon?

Both of my 83 cars used a demister timer relay - 10 minutes. The rocker switch was momentary, and the only thing that might melt it would be the light bulb that lets you know it is working-- all the current was passed through the external relay contacts. The one 83 I have is a 242GLTi with just about every convenience known to 240s, but the other was just a steel-wheeled DL sedan. Both had the timed demister.

But I wouldn't be surprised, just maybe a little jealous, if the aftermarket replacement windows had a beefier defroster grid. I'd make accomodations for it in a flash (wire in a 40A cube relay at a minimum) and check the real current drain to be sure the wiring and fusing is adequate. Most of my cars have only a couple working grid lines left.
--
Art Benstein near Baltimore

I guess that does it then -- probably the new window that did it (sedan, right). I'll wait until a warm day, then wire up something a little heftier for the switch, the fuse, and maybe even pull a new heavier-guage wire through the floor.

I won't be getting down to the junkyard anytime soon for a new switch, so I'll just have to use my hardware store toggle switch (20A 120VAC) for now, and hope it doesn't melt as well.

Regards,
-Kevin

Gotta be careful stepping through the junkyard when you can see the ground, but you must have a foot of snow over the parts now.

Here's the post inspiring my deja vu comment, if misery likes company.

http://www.brickboard.com/RWD/index.htm?id=906484
--
Art Benstein near Baltimore