AMC Eagle Den Forum

The Shop => Electrical => Topic started by: vangremlin on March 08, 2013, 08:59:23 AM

Title: Rear Defroster Switch
Post by: vangremlin on March 08, 2013, 08:59:23 AM
Has anyone ever changed from the original push button style rear defroster switch to the later years toggle style?  I know the push button switch leads to a relay on the steering column, while the toggle style goes directly to the rear defroster.

The reason I'm interested in changing is because my defroster won't turn off on its own.  You have to turn the car off.  Does the toggle style turn off after a certain period of time, or at least allow you to toggle the switch to turn it off?  Thanks.
Title: Re: Rear Defroster Switch
Post by: eaglefreek on March 08, 2013, 09:36:25 AM
I have the toggle version and my turns off by itself or you can turn it off manually.
Title: Re: Rear Defroster Switch
Post by: BenM on March 08, 2013, 12:31:05 PM
I have not, but make sure you disassemble the new switch and lubricate it with silicone grease so the switch doesn't break off.

I may have the connector end for a switch laying around if you want it.
Title: Re: Rear Defroster Switch
Post by: vangremlin on March 08, 2013, 02:18:48 PM
Quote from: BenM on March 08, 2013, 12:31:05 PM
I have not, but make sure you disassemble the new switch and lubricate it with silicone grease so the switch doesn't break off.

I may have the connector end for a switch laying around if you want it.

Thanks for the tip.  The switch I have seems to operate pretty smoothly but an ounce of prevention makes sense.  The connector end you're referring to - you mean the pigtail that plugs into the back of the switch?  I have that also, but thanks for the offer.
Title: Re: Rear Defroster Switch
Post by: JayRamb on March 08, 2013, 06:25:55 PM
My switch turns off around 10-12 minutes. I have an 87.
Title: Re: Rear Defroster Switch
Post by: BenM on March 09, 2013, 11:13:00 AM
Quote from: vangremlin on March 08, 2013, 02:18:48 PM
Thanks for the tip.  The switch I have seems to operate pretty smoothly but an ounce of prevention makes sense.  The connector end you're referring to - you mean the pigtail that plugs into the back of the switch?  I have that also, but thanks for the offer.

That's what I meant. I went through three before I realized how easily they come apart. The first really cold day when it didn't bind was nice.
Title: Re: Rear Defroster Switch
Post by: carnuck on March 11, 2013, 08:52:09 PM
There is a timer in the relay of later ones. Earlier ones didn't have it.
Title: Re: Rear Defroster Switch
Post by: vangremlin on March 11, 2013, 09:46:21 PM
Thanks everyone for your responses.  Sounds like thats the way I want to go, now I just need to figure out how to change the wiring from the old relay to the new switch.
Title: Re: Rear Defroster Switch
Post by: vangremlin on March 16, 2013, 02:30:27 PM
I dug into this a little bit more.  Seems pretty straightforward.  The 81 version is pretty basic, you have the switch, which triggers the relay, which goes to the rear window defroster and the small indicator light in the radio bezel.  In the newer version, the relay is housed with the switch, and the light is built into the switch also.  The only question I'm coming up with is that there is a light blue wire (14 ga) that shares the same terminal coming out of the switch as the light blue wire (16 ga) that goes to the rear window defroster.  The attached schematic from the Eagle Nest download section shows the 14 ga wire going to a diode, and then on to P9.  Since the original switch didn't control anything else, I figure that I don't really need to worry about this 14 ga wire.  Anybody have any different thoughts?  Thanks.

http://www.amceaglenest.com/images/Downloads/Rear%20Window%20Defogger.jpg
Title: Re: Rear Defroster Switch
Post by: BenM on March 16, 2013, 08:29:09 PM
I believe that diode is part of the famous "Diode Trio" that triggers high idle when the defroster, headlights, or air conditioner is on. It's under the hood and part of the harness somewhere. I don't know offhand if they were used pre-computer.
Title: Re: Rear Defroster Switch
Post by: vangremlin on March 16, 2013, 08:41:35 PM
Thanks.  I've switched over to Gronk's Motorcraft carb so I guess it wouldn't come into play any longer, even if it was there to begin with.
Title: Re: Rear Defroster Switch
Post by: ammachine390 on March 17, 2013, 03:55:51 AM
Quote from: BenM on March 16, 2013, 08:29:09 PM
I believe that diode is part of the famous "Diode Trio" that triggers high idle when the defroster, headlights, or air conditioner is on. It's under the hood and part of the harness somewhere. I don't know offhand if they were used pre-computer.

On 81 models, the idle speed control was different than the later years. The diode pack is not part of the harness. There is another box that looks like a smaller ignition module in the back of the engine compartment on the passenger firewall that is labeled "idle speed control." That box is the diode pack. All 81 models had, whether or not they had the computer, as they were separate systems. Also on 81 models, the idle speed did not increase when the headlights were turned on, that started in on 82 models. The other thing that raised the idle speed on 81 models (possibly later models too, not sure) was if you turned the steering wheel to one side all the way, not exactly sure how that triggered a higher idle speed though.

Anybody else's Eagle, that's not an 81, raise the idle speed for steering turned all the way to one side?

Quote from: vangremlin on March 08, 2013, 08:59:23 AM
The reason I'm interested in changing is because my defroster won't turn off on its own.  You have to turn the car off.  Does the toggle style turn off after a certain period of time, or at least allow you to toggle the switch to turn it off?  Thanks.

Mine doesn't either. I pulled the relay apart to look inside it, found nothing that really looked abnormal though.
Title: Re: Rear Defroster Switch
Post by: vangremlin on March 17, 2013, 09:23:28 AM
Thanks for the info ammachine 390.  I've got that idle speed control box on mine.  I guess its just dead weight now that I've Gronked my car!
Title: Re: Rear Defroster Switch
Post by: BenM on March 17, 2013, 01:31:03 PM
Quote from: vangremlin on March 17, 2013, 09:23:28 AM
Thanks for the info ammachine 390.  I've got that idle speed control box on mine.  I guess its just dead weight now that I've Gronked my car!

You could pick up an idle solenoid that fits the 2100 series and install it. That's all it should need.

I'm fairly certain that the later Eagles did not change idle based on power steering, but the computer did monitor idle speed and could use the vacuum part of the sol-vac to force open the throttle if it dropped too low.

I would expect a pressure sensor mounted on the high pressure hose if that was used to control idle.
Title: Re: Rear Defroster Switch
Post by: carnuck on March 18, 2013, 12:34:43 AM
Quote from: ammachine390 on March 17, 2013, 03:55:51 AM
Quote from: BenM on March 16, 2013, 08:29:09 PM
I believe that diode is part of the famous "Diode Trio" that triggers high idle when the defroster, headlights, or air conditioner is on. It's under the hood and part of the harness somewhere. I don't know offhand if they were used pre-computer.

On 81 models, the idle speed control was different than the later years. The diode pack is not part of the harness. There is another box that looks like a smaller ignition module in the back of the engine compartment on the passenger firewall that is labeled "idle speed control." That box is the diode pack. All 81 models had, whether or not they had the computer, as they were separate systems. Also on 81 models, the idle speed did not increase when the headlights were turned on, that started in on 82 models. The other thing that raised the idle speed on 81 models (possibly later models too, not sure) was if you turned the steering wheel to one side all the way, not exactly sure how that triggered a higher idle speed though.


I took the idle speed box off mine. Since I plan to go EFI then liquid propane injection later I didn't need it or the cat.

QuoteAnybody else's Eagle, that's not an 81, raise the idle speed for steering turned all the way to one side?

Only 4 cyls had that AFAIK. It's a pressure switch on the power steering high pressure hose.
Title: Re: Rear Defroster Switch
Post by: skuhler on December 06, 2013, 04:38:56 PM
On my 86 Eagle SW, it looks like the defroster switch is broken off at the dash.  Would that have been a push button or a toggle?
Title: Re: Rear Defroster Switch
Post by: Prafeston on December 06, 2013, 06:09:58 PM
It's a toggle.
Title: Re: Rear Defroster Switch
Post by: Prafeston on December 06, 2013, 06:14:12 PM
(http://i.imgur.com/8IlzQ5I.jpg)

Title: Re: Rear Defroster Switch
Post by: captspillane on December 07, 2013, 01:31:02 PM
Good luck finding one that isn't broken. The toggle is a brittle black plastic with a big hole in the center for a clear plastic to light up from the bulb behind it. You're not alone with a broken one. It is very weak and more often broken than not.

To make replacement tricky the back of the toggle is a large assembly that I'm guessing includes a timer. If you put a steady on toggle on it will behave differently than the factory thought it should. I'm curious if leaving it on too long will damage the element strips across the window.
Title: Re: Rear Defroster Switch
Post by: vangremlin on December 07, 2013, 03:09:20 PM
The toggle versions included both a relay and a timer.  The older push button versions were just that, a push button that led to a relay on the brake pedal support assembly.  They stayed on until you turned the car off.  I've been lucky enough to find a few of the toggle variety in the junk yards.  If you wanted to replace it with just an off the shelf toggle switch, I don't think the heating elements would get damaged, but I think you would need to put a relay in the circuit.
Title: Re: Rear Defroster Switch
Post by: Amc1320 on December 07, 2013, 06:11:06 PM
Hey Prafeston what model CB is that?

Did it fit right in the ash tray hole?

I really want to get a CB and I have been looking at the small ones with that same idea, but it looks perfect in your pic!

Rob
Title: Re: Rear Defroster Switch
Post by: Prafeston on December 07, 2013, 06:17:41 PM
I have no idea on the CB, though I do recall a member talking about fitting a small CB in the ashtray hole. Not sure what if any modding/cutting needed done, but it sounded pretty simple! This was just a pic I snagged from Google Images that had a good shot of the toggles.

EDIT: I found the thread the image was snagged from.

http://forums.amceaglesden.com/index.php?topic=41988.0
Title: Re: Rear Defroster Switch
Post by: Amc1320 on December 07, 2013, 06:21:48 PM
Ok thanks, I can see its a Midland, maybe I can search some specs and see what they have

Now to just come up with a good handle......
Title: Re: Rear Defroster Switch
Post by: Prafeston on December 07, 2013, 06:25:33 PM
I'd love to get a stock CB radio, but seeing as how even a used AMC CB Radio goes for over 300 on eBay that may never happen!
Title: Re: Rear Defroster Switch
Post by: IowaEagle on December 07, 2013, 06:28:24 PM
If need be you can retrofit a Grand Wagoneer one in.  It is probably not as prone to breaking at the OE one.  http://www.teamgrandwagoneer.com/search.php?search_query=defogger&x=0&y=0
Title: Re: Rear Defroster Switch
Post by: skuhler on December 07, 2013, 07:57:55 PM
Thanks for the info.  I thought it would just be a switch, it's interesting to know it's got a relay in it too!  Have you (or anyone) had any luck opening up the switch and changing out the plastic toggle piece?
Title: Re: Rear Defroster Switch
Post by: IowaEagle on December 07, 2013, 08:07:32 PM
I think someone here has done that, successfully.  Perhaps they will chime in.   Yes, the switch contains the timer on the OE ones.
Title: Re: Rear Defroster Switch
Post by: vangremlin on December 08, 2013, 09:11:41 AM
Quote from: IowaEagle on December 07, 2013, 06:28:24 PM
If need be you can retrofit a Grand Wagoneer one in.  It is probably not as prone to breaking at the OE one.  http://www.teamgrandwagoneer.com/search.php?search_query=defogger&x=0&y=0

Thanks for posting that link IE.  I'm not certain it would be a direct swap wiring-wise because they don't have a good picture of the back, but I'm sure it could be made to work.

Next time I'm at the junkyard I'll look at some defroster switches from various cars to see if any might work in an Eagle.
Title: Re: Rear Defroster Switch
Post by: skuhler on December 08, 2013, 11:37:22 AM
I worked on it a little this morning to see if the switch even works.  I can rocker it up and the light behind the switch illuminates.  Once I release it, the light goes off.  Does that mean its working?  Should the light stay on as long as the timer is on?  I checked for voltage on the grid, driver's side, but I didn't get any. 
Title: Re: Rear Defroster Switch
Post by: 1985amceagle on December 08, 2013, 12:12:12 PM
The light should stay on until the timer shuts it off along with the grid.
Title: Re: Rear Defroster Switch
Post by: skuhler on December 08, 2013, 04:05:24 PM
Thanks for the help.  Great forum!