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The Foc Winter Car Issues Thread

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Hello Fellow Ford Fans!

After many many posts popping up asking similar questions, we at FOC have decided to put together a little thread of known issues and troubles that rear their ugly heads during the winter months! Of course these issues aren't the be all and end all but it may go a little way to diagnosing your issues!


Your battery is vital, without it, your car may as well be a toaster! battery issues tend to happen in colder months because of the stresses and strains you put on them during the colder seasons, heated screens, heated seats, colder operating temps, using lights more, heating glow plugs (Diesel only) all consume power. Getting into your car first thing on a -5*c morning, and expecting the battery to cope with all the electrical things is a tall order!!

Cold ambient temps can cause battery's to fail, Car batteries produce electrons through chemical reactions. During cold weather, the battery's chemical reactions take place more slowly, meaning they are producing fewer electrons with which to power the engine. In addition, the engine's oil thickens during cold weather, causing the engine to require up to three times as much power to turn over.

All this extra power needed will drain the battery mischief quicker.

Symptoms of a dodgy battery will be poor or non starting (usually accompanied by a clicking sound)

You can self test your battery by turning on the ignition and testing the battery with a multimeter, then turning on high drain items like heated screens or main beam, and seeing how much the battery drops or starts to discharge. A healthy battery should last a while and not discharge too quick or drop it's voltage much.


Your alternator charges your battery, but also supplies your car with all the electrics you need when driving. Similar to the battery, in the colder months we put a lot more strain onto the alternator. We ask it to run heated screens, seats, fans for blowing the hot air into the car, running lights, sometimes fog lights also, run the radio, use the wipers... All in all your asking it to provide a lot!! Sometimes on a worn alternator this can be too much!

Alternators can overheat, if the engine is left running for periods of time with no movement, typically like when you leave the car to defrost or warm up on a frosty day... Add this to the exta power your wanting it to provide and bang... The end of your alternator. I had this once, and had smoke coming from under the bonnet! What had happened was the bearings inside had overheated due to being run for long periods of time and the bearings had collapsed. Luckily just a new alternator shaft was needed.

Alternators also have diodes in, to convert the alternating current into direct current, to charge your battery and supply the 12v (well anywhere between 13-15) that your car needs. If one of these diodes fails, the alternator then cannot supply the required power.

Symptoms are a regularly flat battery, and maybe dim lights. You can test the alternator yourself, by putting a multimeter across the battery when the car is running, however now with smart charge systems, it's not as easy to self diagnose, as the alternator/ECU will regulate the amount of charge given to the battery.

Starter Motors:

In cold weather it takes a lot more energy and work to start a car. This added strain can cause starter motors to overheat.

If your vehicle has trouble starting on cold mornings it's more than likely one of the other issues, however if you keep trying to crank the car without it starting its important you stop and let things cool/settle... A starter motor can and will overheat if you try to crank the car for prolonged periods of time.

Starter motors can also get "sticky" after time, and the problem can be temporarily solved by a gentle tap with a block of wood or similar... I am not for one minute suggesting that you try this when you car refuses to start, especially in the colder months, but this could be a symptom in the warmer months!

Similar to a battery, symptoms will be poor or non starting and maybe a click from the starter motor.

Fuel Filters:

This is more geared for Diesel Owners, as petrol doesn't get affected in the same way.

When diesel gets cold, it suffers from waxing or gelling, this means that below a certain temperature wax molecules start forming in the diesel. These molecules then start clumping together forming larger flakes, which in turn stick to things... Normally fuel lines, fuel filters, injector nozzles... Anywhere where the fuel runs! This of course can cause fuel starvation, meaning your engine will stall, go into limp mode, etc etc.

Once a fuel filter becomes blocked it's often easier and cheaper just to replace it, rather than to try running additives through it to clean it. One thing I will stress is that most TDCi engines appear to be quite fussy on fuel filters, with many being a pig to reprime and start if using a non ford item. I know this from personal experience!

Manufacturers have built in ways to combat waxing, by putting in an Excess Fuel Return system, or a spill return system, by which any excess fuel from the injector pump and injectors is returned to the fuel tank. Once the engine has warmed, returning warm fuel prevents waxing in the tank.

Fuel suppliers also do their bit by supplying "Winter Diesel" this basically has some additives added, to prevent the waxed molecules from joining together, these additives however do not stop the waxing itself.

There are some things you can do to prevent this, adding winter additive yourself, fitting a diesel pre heater.

In days gone by, people used to add a little petrol, or kerosene. A practice still used by some Land Rover owners, however doing this on a modern TDDi or TDCi unit will be sending your car to an early grave! DO NOT add petrol or kerosene to your fuel!

Symptoms of a blocked filter will be poor starting or non starting, limp mode or stalling when driving. You may also get either a glowplug warning light or the engine management light.

Fuel Filter Housings:

Something which I luckily seem to have avoided, however many colleagues and members on here have suffered with it!

In the cold, things contract or get smaller. Something that appears fine when warm can give faults and issues when it's operating temp lowers substantially. Plastic is also known to get more brittle and fragile when cold.

If you have a cracked fuel filter housing you may not necessarily know about it in the warmer months or once the car is up to running temperature, however when cold te plastic will shrink slightly, opening up any hairline cracks, letting air into your fuel system, and probably also forcing fuel out! Tell tale symptoms are the car stalling or going into limp mode when cold, but appearing to drive well when warm. Again warning lights on the dash!

This can often be overlooked when people complain of running issues, so make sure you have a poke around first and double check.

Glow Plugs:

Again a diesel only thing. I could get technical and talk about thermal diffusion, but I won't! Basically for a diesel to start efficiently and easily, the cylinders have to be warmed in colder temps. This is done by glow plugs! They only operate for seconds, if that! But If they fail then you end up throwing diesel into a cylinder that's stone cold, and it takes longer to start. Obviously issues occur in winter as this is when the glowplugs are needed the most.

Again symptoms of dodgy glowplugs will be rough or prolonged starting, white smoke from exhaust (note smoke and not steam from condensation) and a strong smell of unburnt diesel. You may get the glowplug light flashing on the dash, but in my experience you don't get this unless they are well and truly dead!!

Glow Plug Loom:

With the extra power needed to run the glowplugs for longer, this can of course cause wiring looms to work harder. On the end of the glowplug rail (some cars have this some don't) you will find a ring connector on the end of a wire, this can burn out and melt, causing a bad connection to the glow plugs. This means the glowplugs either aren't getting the full voltage or may have gone faulty and drawing more power than they should. This is easily sorted by chopping the loom back to a good bit of wire and recrimping a ring connector onto it. I have been reliably informed that this is how the main dealers do it unless the loom is completely burnt or it's too short.

Symptoms will be similar to above, however if you lift the bonnet and get someone to crank the car over for you, you may be lucky (if you think of it that way) to see some smoke coming from the burnt end of the loom! Also look for black burnt ends on cables near the location of glowplugs.

Forum Member big_dav3 has also created this handy winter survival guide. To make sure you don't get caught out this winter visit The Winter Survival Guide

I hope that this thread has helped some of you diagnose your cold weather issues! This list is of course not extensive and there are many other things that could be causing your issues but these are a good starting point!

Thanks for reading!

The FOC Team.

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