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Author Topic: Electrical contacts in cold weather.  (Read 3324 times)
G8JNJ
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« Reply #15 on: March 07, 2012, 12:13:24 PM »

I'd suspect the battery - I've had several cars which start OK in the warm weather but do nothing when it gets cold - it's always been the battery.

In the cold the battery efficiency falls off and the cranking current increases due to the engine lube getting thicker. This dramatically reduces the voltage available on start.

Try leaving the battery on trickle charge overnight. This will keep the cell temperature up. Then see if it starts OK in the morning. If it starts OK then it points to the battery. If it doesn't it's something else.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com
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W8JX
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« Reply #16 on: March 07, 2012, 12:58:51 PM »

The conductivity of the metals used in wiring and electrical connections doesn't change significantly in cold weather.

If it changes at all the resistance decreases slightly as temperature drops.
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WA8MEA
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« Reply #17 on: March 07, 2012, 03:54:43 PM »

W8JX is right on the money.  In theory, they ought to be more conductive since metal contracts in the cold.  So metal on metal ought to equally contract.

So far, I like the moisture between the contacts theory.  It freezes and spreads apart the contacts.  In the spring/summer, the sun is warmer, the engine and body are warmer and the warmer winds are blowing, evaporating any moisture away from the contacts fairly rapidly.

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W5FYI
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« Reply #18 on: March 07, 2012, 06:41:18 PM »

Actually, if it gets cold enough, you might begin to see superconductivity!
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KE3WD
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« Reply #19 on: March 07, 2012, 07:22:48 PM »

My realworld experience with the Ford system is what I'm referring to here.  He's replaced the fuel pump.  Cold weather can indeed make the relay work a bit better than before. 

Again:  Try switching the Fuel Pump relay with the Air Conditioner relay and then see if the Fuel Pump works a bit better.  When it does, replace the relay that is now in the Air Conditioner slot, before the weather gets so warm as to require use of the Air Conditioner. 

Beautiful thing, using the same relays for at least three functions like that, I've gotten several people back up and running out on the road because of that. 


73
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G8JNJ
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« Reply #20 on: March 08, 2012, 03:02:06 AM »

I suspect a lot of seasonal changes in engine performace / ability to start are actually due to minor variations in the fuel / air / water vapour mix rather than just temperature affecting electrical contacts.

I'm sure another one of my old cars used to start much better when it was foggy  Undecided
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W4VR
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« Reply #21 on: March 09, 2012, 05:46:09 PM »

It's a Ford, that is why?  Buy him a Caddy and drive in peace!
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KA4LFP
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« Reply #22 on: March 09, 2012, 06:16:18 PM »

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 agree with the author of this post --
Electrical connections do contract when they're cold, especially the bimetal alloys that a lot of cheaper connectors are made of these days.
That may not completely break the circuit, but it will add resistance, as the connection isn't good.

I'd suspect a bad ground -- my old Taurus years ago had a bolt on the firewall where multiple wires arrived for grounding. That was behind the engine, and got somewhat corroded. Talk about causing some really weird problems, and made worse in cold weather.....
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W8JX
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« Reply #23 on: March 09, 2012, 07:17:53 PM »

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 agree with the author of this post --
Electrical connections do contract when they're cold, especially the bimetal alloys that a lot of cheaper connectors are made of these days.
That may not completely break the circuit, but it will add resistance, as the connection isn't good.


Not really because BOTH SIDES of pin contract (blade and socket) and they are not dissimilar metals.   What happens is that the plastic connector housing contracts/expands and  can cause contacts to break connection if they are dirty. The harness can also shrink when cold and change stress on connector.
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