How does the cigarette lighter know when to "pop out?"

Hi group:
I recently changed the wiring on my 1985 Cadillac Cimaron's cigarette lighter so that the ground side of the electric fan solenoid is
grounded when I push the cigarette light in; and hense, the fan turns on. (There are some other problems with the circuitry related to the electric fan that prevent it for working normally.)
With the wiring the way it is, there's very low voltage applied thru the cigarette light so it no longer gets hot but it makes a good ground connection (like an off/on switch) and runs the radiator fan.
The above described mod seemed to work fine for a few days but all of a sudden, when I push the cigarette light in, it pops out immediately. To turn the fan on, I had to hold the lighter in; not a very convenient way to cool the car when the weather is warm here in southern Oregon.
What is causing the cigarette ligter to behave in this manner?
I took the lighter and plugged it into my other car (1995 Pontiac Grand Prix) and it stays in and works fine there.
I took the lighter from the Pontiac and plugged it into the Cimarron and it stays in and turns on the fan motor.
Is this an X-files matter? I look forward to your suggestions.
Regards, Al Gershen Grants Pass, OR snipped-for-privacy@hotmail.com
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If you must cobble something together instead of repairing it correctly couldn't you at least spend the 99 cents to buy a damn toggle switch? Hooking the fan to the cig lighter has to be one of the dumbest things I've heard in quite a while! Bob
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Every time I find myself saying that, I end up being proven wrong eventually. Someone, somewhere *is* just that stupid.
nate
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snipped-for-privacy@hotmail.com (Al Gershen) wrote:

Actually, it makes an absolutely LOUSY ground connection if you've got it wired so that the juice is going to ground through the heating element of the lighter. No, I take that back - It makes a *HIDEOUSLY* lousy ground.

The lighter pops out when it gets hot. The outer ring is a springy material that loses some of its spring as it warms, releasing its friction-grip on the hole it's plugged into. Eventually, it releases enough so that the tension you put on the spring inside the part you pull out (usually invisible, but it is there, hiding under everything else) overcomes what little "grip" is left, and out pops the lighter.
If you've grounded a heavy load (and the heater motor is one of the heaviest electrical loads that exist on a car) to the shell, it's *VERY* possible that the juice now going to ground there is producing enough heat to pop the lighter. If you've been running it this way for anything more than a few minutes, the possibility also exists that you've "cooked" the retaining gizmo on the lighter enough that it's "forgotten" that it's supposed to be a springy object.
Strongly advise that you find *SOMEPLACE ELSE* to ground the blower. Just about anything metal that's also solidly attached to the chassis with metal will work just fine.
--
Don Bruder - snipped-for-privacy@sonic.net - New Email policy in effect as of Feb. 21, 2004.
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On 2 May 2004 19:58:35 -0700, snipped-for-privacy@hotmail.com (Al Gershen) wrote:

Dang Dude.. I know times are hard for a lot of folks out there but surely you can scrape together a buck for a switch! A cigarette lighter does not make a good switch. You going to end up burning out a hundred dollar fan motor to save a buck.
Steve B.
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Why not just get a switch? If it's the resistor wire block for the fan, just get some new resistor wire if it's too much to replace the block. Or just solder the broken resistor wire together for a little more life.
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Actually, I have seen something like this done intentionally as a theft deterrent.
The modified cigarette lighter was rigged in series with the wire to the fuel pump. When you leave the car, put it in your pocket.
A switch would have done as well, but might have been a bit easier to spot.
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spot.
And when the lighter is misplaced?
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Stick a screwdriver or other metal object in to make the connection.
Tim
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I have done this! I didn't even take the lighter with me. NOBODY was gonna figure that out in the heat of a felony!
--
Alan Gallacher
Born to Tinker!
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It "sounds" like a good idea, but you will find that your fuel pump will have a shortened life because the lighter will limit the voltage reaching it and make it run hotter, thus fail sooner. If you like the stealthy look of the lighter for a switch, I would suggest that you at least solder a wire across the heating element in the lighter so that there is a direct connection to pass power to the fuel pump. This is assuming that the lighter has been modified where either the ground or the hot wire has been removed and the fuel pump power leads re-routed to the lighter for use as a switch. If that isn't the case then that jumper will make a mess of your electrical system. I figure anyone that has enough knowledge to attempt rewiring this way, would understand what I mean.
Tim

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This was the 'modified' disclaimer I referred to in my post. The cigarette lighter becomes a 'dummy'. You gut it, disable the resistance coil. The old +12 and ground are removed, and the fuel pump wiring is rerouted to this.
The first time I ever saw this was in the old Fiero Club. Fiero's were stolen like crazy here in Houston, for the seats. Seats were fenced to junkyards, which then sold them back to the insurance companies. Those damn seats cost about $1800. It was a vicious circle.
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On Tue, 4 May 2004, t_puls wrote:

THough I agree his cigarette lighter switch is dumb, it's not for this reason. He said he's triggering the fuel pump *relay* with the lighter.
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The cigarette lighter switch was both dumb and ingenious. It required the modifications to the lighter and rerouting of the fuel pump control wires. It seemed to make sense in 1984 when this was happening.
After my Fiero was stolen, I just started taking the fuel pump fuse out if I were in an unsafe area.
Apparently we didn't have have the emphasis on good antitheft devices in those days. The feeling was that a good car thief could disable most of them within seconds. Rigging the electrics stopped some of them.
Some of these guys could take an engine out of a car and be gone in just a few minutes. One or two of them went to Jesus while doing it, too.
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While you may have gotten this to work you may have damaged the fan motor. If you look at what Ohms Law says you will see that the lighter introduces resistance into the fan circuit. That means that the fan motor is running on a reduced voltage. Over time the fan motor winding will run hot and the motor will rapidly age and fail. A failing motor will draw more current which in turn might be whay the cigarette lighter is not beginning to pop out. At this point it sounds like the lighter is acting like a circuit breaker for the fan. While I cannot tell for sure that this is happening without taking amperage measurments on the fan motor, I can tell you that this arrangement is not your best option as others may have already mentioned. Your best bet is to use a good old fashioned toggle switch from Radio Shack or Home Depot.
Tim
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