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Author Topic: Electrical contacts in cold weather.  (Read 3270 times)
WA8MEA
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« on: March 07, 2012, 04:50:58 AM »

My son will soon be driving a Ford Taurus on his own.  All winter we have been battling an electrical problem that rears its ugly head ONLY in cold weather.  But isn't that what usually happens in cold weather?  Your battery connections seem to act up when it's cold.  Even car audio equipment can act up in the cold.

The fuel pump won't kick in. (We replaced the fuel pump....)  However, on this beautiful 50 degree morning....the first since October....it fired up the very first turn of the ignition!  

SO....what is it about cold weather that makes connections less.....conductive? ? ? ?

73, Bill - WA8MEA
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KS2G
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« Reply #1 on: March 07, 2012, 05:01:49 AM »

Maybe it's the battery, not the connections.
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W8JX
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« Reply #2 on: March 07, 2012, 05:34:07 AM »

Maybe it's the battery, not the connections.

I agree that while it might be battery it maybe also be something else. There is a connection that is effected by temperature here. My guess is is a harness connection somewhere that changes with temperature. I have seen this before.  I would check/reseat EVERY connector in that cars harnesses for starters.

Also I might add that the Taurus is known for phantom fuel pump issues and this is not a rare problem.
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K5LXP
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« Reply #3 on: March 07, 2012, 05:49:55 AM »

The fuel pump won't kick in. (We replaced the fuel pump....)

The fuel pump relay is 2nd in line then.  It's an ice-cube relay in the under-hood fuse block.


Mark K5LXP
Albuquerque, NM
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W5FYI
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« Reply #4 on: March 07, 2012, 06:36:26 AM »

It's an off chance, but if water gets into a connection, then freezes, its expansion could possibly push contacts apart, resulting in an open circuit.
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AA4PB
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« Reply #5 on: March 07, 2012, 06:49:56 AM »

I had a Ford that had fuel pump issues cause by the computer module under the dash. When you turn on the ignition the computer activates the fuel pump for a few seconds in order to pressurize the fuel lines. That circuit was bypassed once you start cranking the engine so it would eventually start if you didn't run the battery down first. So, it could be that the computer is being affected by the cold temps and not running the fuel pump to pressurize the lines.

You can often hear the fuel pump run for a few seconds if you turn on the ignition but don't crank the engine.
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NR4C
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« Reply #6 on: March 07, 2012, 06:58:29 AM »

I also found that if you run out of  gas, you must cycle the ignition switch to turn on the fuel pump at least 3 time before you get enough fuel in the lines to get pressure to start and run the engine.  When you trun on the key, it runs the pump for a few seconds, and if it doesn't get pressure, it shuts off so as not to mess up if there is a leak.

...  bill  nr4c
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VA7CPC
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« Reply #7 on: March 07, 2012, 07:01:45 AM »

I hate to belabor the obvious, but:

. . . Have you cleaned, greased, and tightened your battery connections?

Silicone "dielectric grease" is available at auto parts stores.  It keeps corrosion problems away for a long time.  If you disassemble the connectors, grease the contacts when you put them back together.

           Charles
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K1CJS
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« Reply #8 on: March 07, 2012, 07:13:25 AM »

There are so many differnet points that can be looked at that you can 't list them all.  How about the connection from the negative battery terminal to the chassis?  Even a ground strap between the engine and the frame/chassis could be the culprit.  The battery cables--not only at the battery, but at the other ends where they connect to the chassis, starter, distribution block, etc. could be loose or corroded.  Conncetions could shrink from the cold and remake themselves when things warm up.

One time I worked on a friends car that had electrical problems similar to what you describe.  We checked the connections all over the place, and finally found the trouble--a crimp commection in the wire fron the negative battery cable to the wire to the chassis.  The battery cable was a replacement, and the wires had corroded down to almost nothing in the crimped on section.  That just goes to show that it could well be anywhere--even at the fuel tank ground connection (strap?) to the car body itself.
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W5FYI
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« Reply #9 on: March 07, 2012, 07:24:39 AM »

"That just goes to show that it could well be anywhere--even at the fuel tank ground connection (strap?) to the car body itself."

You might ought to run a line parallel to the suspect line, just to see if that cures the problem.
   
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K8AXW
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« Reply #10 on: March 07, 2012, 08:45:14 AM »

With these modern automobiles there are so many things that can create this problem that the chances of solving it here on eHam.com are slim to none.

Take the thing to a dealership and let him solve it.  Sure it's going to cost bucks but an unreliable car is actually dangerous. 

I just went through a similar problem with my Lincoln Town Car.  It wasn't the ignition but a defective air flow controller that monitors the temperature and flow of air the engine is demanding.  The information provided by this valve is calculated by the engine computer and sets the mixture and god only knows what else for the engine to run smoothly.

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WA8MEA
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« Reply #11 on: March 07, 2012, 11:06:40 AM »

Gee, fellas.  Thanks for all the advice on the Taurus!  That's great.  However, my query was really about why cold weather makes electrical connections less....conductive.

Since I survived a VERY mild winter without many starting problems, I am just going to use the car all spring, summer and into the early fall without worrying about anything. (She starts right up in the warmth....)  At that point, I will probably replace the battery, since it will probably need it by then....and also replace the clamps. (Yes....we've cleaned those up.)  Who knows, that might do the trick.

The problem is, there are just so many possible issues and I don't feel like throwing money at it right now. (Especially since the weather has warmed....)  You can have an endless string of expenses with an issue like this.

Could even be the ECM....

But back to the original question, since I promised my 17 year old that I would try and find an answer for him.... because I didn't have one!   Embarrassed

Why does cold weather make electrical connections less....conductive?
« Last Edit: March 07, 2012, 11:09:45 AM by WA8MEA » Logged
W8JX
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« Reply #12 on: March 07, 2012, 11:33:26 AM »

Gee, fellas.  Thanks for all the advice on the Taurus!  That's great.  However, my query was really about why cold weather makes electrical connections less....conductive.

Actually they should in theory be more conductive. You likely have some bad connections which open up/loosen marginally in cold temps when parts contract. I might add that I have used snow plow and spreader equipment for over 20 years in temperatures below minus 20 at rimes and I never have had issues with connections failing if they were tight and clean. The big two pin plug feeding plow pump motor can see over 150 amps at times and I have NEVER had a problem with them. I have had issues with connectors for spreader on rear of trucks that can see 30 amps at times but solved that many years ago by taping/sealing those connections better with electrical tape. (plow connectors are self sealing)
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KE3WD
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« Reply #13 on: March 07, 2012, 11:37:33 AM »

The fuel pump won't kick in. (We replaced the fuel pump....)

The fuel pump relay is 2nd in line then.  It's an ice-cube relay in the under-hood fuse block.


Mark K5LXP
Albuquerque, NM

Exactly. 


Try temporarily swapping the Air Conditioner relay for the Fuel Pump relay to find out.  They are identical. 

Your owner's manual has the key to where in the under hood fuse/relay box these two relays are located. 

73
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AA4PB
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« Reply #14 on: March 07, 2012, 12:05:37 PM »

"However, my query was really about why cold weather makes electrical connections less....conductive."

It doesn't unless there is something else wrong like corrosion or a loose connection. The conductivity of the metals used in wiring and electrical connections doesn't change significantly in cold weather.
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