Relays...

[Deano]

I have reason to believe that my power window relay has gone bad. Using a test light, I'm getting power on the wire from the fuse box, but not on any of the three other terminals (red, black, or white/tan). The single terminal comes from the fuse box and the other three goes to the passenger's side window switch, I believe. I've called and searched and no one seems to have one. Is there any way to repair a relay or any other relays that can be substituted?

 

[Aspen500]

You should also have power on the dark blue wire with the key on as well as the red wire. Dark blue is power to the relay coil and red is power to the relay contacts. Black, of course, goes to ground eventually through the window switch. The way the wiring diagrams are set up, it's kind of tough to follow but I THINK that's correct. It's spread out over 3 different pages. It appears there are 2 fuses. One for the relay coil ckt (dark blue wire) and one for the high amperage ckt (red wire)

As for a new relay, no idea. As a last resort you can get a 30 amp relay from the parts store but you'll have to redo the connections to fit.

You can test the relay by putting power on the terminal with the dark blue wire and then ground the black wire terminal. Then the red and white/tan should have continuity between the two. Use an ohmmeter or if you don't have one, also put power to the red terminal and check for power coming out the remaining terminal.

 

[volare 77]

Will this one work MoPar Electric Window Relay-NOS- Asp / Vol / Le Baron / Diplomat - P/N 3879696 | eBay
looks 3747159 on the relay bracket

 

[Deano]

Will this one work MoPar Electric Window Relay-NOS- Asp / Vol / Le Baron / Diplomat - P/N 3879696 | eBay
looks 3747159 on the relay bracket

I do believe that is the one! I always searched "power window relay". Never thought to search electric. On my bracket, I couldn't really tell if it was 158 or 159. Looking closer, I do think it's 159.
When I turn the key over to "run", the relay would click, but when I used my handy dandy test light, I would get power on the dark blue wire, but not any of the others. Come to think of it, when I try to use my power door locks, that relay clicks, too.

"Buy a project car", they said. "It'll be fun.", they said.

 

[volare 77]

Good you found a NOS one at a decent price compared to some of the other power window relays listed for crazy prices.

 

[Deano]

Good you found a NOS one at a decent price compared to some of the other power window relays listed for crazy prices.

YOU found it. And I appreciate it.

And I also appreciate Aspen500's help. You've helped me out quite a bit, too.

 

[Deano]

I was taking a look at the electrical manual earlier and noticed something I'd never paid any attention to before. The diagram shows a red wire (arrow) that supposedly goes to the power window wiring. It doesn't. It goes under the sill plate to the power seat wiring. It also shows a splice- one goes to the window lift wiring and the other goes to the relay. The only one that I can see that plugs into the three terminal section of the relay is one that runs in with the door lock and window wiring. What am I missing?

Also, when I turn the key to "run", using my test light, with the only wire connected to the relay is the single wire from the fuse box, I get power at the wire and the terminal closest to it. But when I plug in the other connector, the only current I'm getting is from the fuse. I know something's not right, but what the hell is it?!

 

[Aspen500]

That red (12 gauge) wire supplies power to the safety relay which supplies voltage to the power windows, power seats and power door lock systems. There should be a red wire to the relay that has power and is for the contact side of the relay, while the dk blue (20 gauge wire) is for the relay coil. With the key on, there will be 2 terminals with power at the relay and 3 terminals with the relay energized. I see your diagram is slightly different than the '79 I'm going off of. Mine shows the relay being plugged into the fuse panel (glass fuses) where yours must be elsewhere(?). Either way, there must be 2 power feeds to the relay. One low amperage, one high amperage. Hard to tell from what you've said but it sounds like the high amp feed is missing which would make the relay click and energize but it doesn't have any voltage input to send out to the windows.

Can you possibly get some photos and post them?

 

[Deano]

Pic 1 and 2. The red wire from the circuit breaker in fuse position #5 goes straight under the sill plate to the seat motor. That's the only red wire from the circuit breaker. Pic 3 and 4. The red wire from the relay goes and splits off, one going under the dash to the passenger's side door and the other to the unused wiring for 4-doors.

 

[Aspen500]

OK, pics help. Is there power on the red wire at the relay? There should be. It comes from the c.b. to the seats and also has a splice to the relay. I see that yellow butt splice connector in the red wire to the relay which is not factory. That always makes me suspicious and, someone has messed with the wiring in the past for some reason. You may want to try putting power to the relay red terminal with a jumper wire and see if the windows work.

 

[Deano]

The yellow splice is where a bad spot was in the wire and I cut it out and reconnected it with the butt connector. When the key is in "run" and everything is plugged in as it should be, the only power I'm getting is at the wire from the fuse box. If I unplug the 3 wire connector from the relay, I get power at the wire from the fuse and the black wire terminal. By the way, the only way I have to test for power is a regular old test light.

 

[Ele115]

If you don't have an ohm meter, you can open the relay and look inside, but if it's got an open winding you may not be able to see it. You can pretty much just look at the points and that won't be your problem. You need an ohm meter, You can borrow one probably. Do you have any switched 12 volts to the really, should just be when you want the window or whatever? There should be prong 12 volts hot, then another one gets 12 volts when you demand your circuit. That's the one that will close the circuit and allow the higher amperage to go to the load. The switched source is not a high amp one. It just makes the contacts close when they are supposed to. It might be time to check your wiring for an open. I doubt if it's the relay. The relay isn't being supplied, most likely.

 

[Aspen500]

You can buy a volt/ohm meter that would be good enough for what you need, for not much money. You aren't testing computer circuits where you need accuracy down to .001 ohms. At work I have one like that and it was over $300 (also does Hertz, amps, etc), however I need one like that for working on newer vehicles. For circuits on "our cars", a $25 one would work just fine.

The power on the black wire with the 3-pin unplugged is odd. The black wire is ground and should have no voltage. Give the ground connections a good going over. A poor ground COULD cause feedback from other circuits. Also, one of the window motors could be partially shorted to ground internally and cause the same thing. It's hard to say anything for sure because I'm not there in person, but I'll try my best remotely! The loss of power on the red wire with the relay plugged in is odd. I'll do some thinking on that one. It does have battery voltage with the 3 pin unplugged, yes? One other possibility is somewhere the red wire is almost broken off internally. With no load, even one strand of wire will still transmit power. Put any kind of load on it and the power is gone. I got burned a couple times by that one way back when in my early auto tech days. That's why you should always check voltage with the circuit plugged in and the load activated (except on air bag systems!), especially on higher amperage circuits.

There's a saying in the auto repair business. It goes "electricity is not an inanimate object, it is a living breathing being, and it's also a prick". Seems to be true at times.

 

[Deano]

"The power on the black wire with the 3-pin unplugged is odd."

I'm not getting the power from the harness itself, just at the relay terminal. I traced the black wire from the harness. It goes to a ground behind the kick panel. Is it possible the wiring positions at the plug was re-arranged, like the red goes where the black is? This whole deal just baffled the absolute shit out of me.

 

[Deano]

If there was someone that has a '77, '78, or '79 M-body that has power windows that would kindly take pity on this old man and take pictures of their wiring and post them for me, or at least tell what it all looks like down there, it would help out a lot.

 

[Ele115]

I'm not home right now. I have a 78 and a 1981 and everything works. If I test neg for Covid I am going back to Fla ASAP and I'll pull that panel and take you a few pics and give you the voltages at the pins with and without the window switch commanded. I could ohm the replay too for future ref (may help someone else)

 

[Ele115]

If I don't post back by Tuesday, just send me a message in case I forgot or I can't fly yet. I should be home within 48 hours though. I hope to get there before that storm screws up the flights

 

[Deano]

That would be so awesome. Thank you much!

 

[Aspen500]

A couple days ago during lunch at work, I thought I'd check Shop-Key, our on-line service manuals (also TSB's, tips, real world fixes, etc....), and see what wiring diagrams that shows. For whatever reason, those don't show a relay in the system. I looked at '79 and then '89 and the diagrams look exactly the same and that makes no sense. Sometimes going older than about 1990 on there gets sketchy and some info just doesn't exist anymore. Guess it was worth a look anyways..........

 

[Deano]

That's weird, Aspen. You wouldn't have any idea which relay terminal is ground, would you? I have a few spade terminals that I was going to use to switch the wiring up a bit just to see what might happen. I already know that I have power at a ground wire, so switching things around wouldn't hurt any. Been kinda thinking that maybe the previous owner may have tried to use a different wiring harness for some reason. Maybe the wiring itself is bass ackwards.