Volkswagen Electrical Problems

Volkswagen Electrical Problems

Electrical problems will invariably affect each and every new Volkswagen vehicle on the road today.  Generally, electrical problems are relatively easy to trace and repair, if you know what you doing, but it can be a nightmare when the faults present themselves as intermittent, especially considering cars have now gone CAN Bus, LIN Bus, Byteflight, MOST, Flexray, Zigbee, etc. VW EPC problems tend to be seriously intermittent, making every VW with an EPC issue a real bitch to diagnose.  Of late, more and more VW cars seem to be having EPC trouble among other bizarre electrical problems and very surprisingly, the VW service centers seem unable to repair them. 

Virtually everyone I know who has had an EPC issue, had to take their cars for repairs at least three to four times for exactly the same fault.  There are also numerous VW, SEAT, SKODA and Audi owners, who spent enormous amounts of money on replacement of "EPC issue causing components", yet the EPC faults remain. Essentially they lost money but I normally say they didn't loose money but bought experience and they paid dearly for it. Then there are others who are still waiting on the VW service agents / or some mechanic for their EPC problems to be solved after several months, a year and in some cases even longer.  

There was a time when virtually every electrical issue or loom (wiring harness) problem was associated  with the  FIAT brand. People even ascribed a nomenclature to FIAT - "First In All Troubles". However, it seems like Volkswagen  subsequently bought that patent, and now owns all right to it.

Electrical problems have never been as common place as they are today.

Let me give you an example, the wiring harness between the alternator and  the a  high voltage fuse box mounted on the battery of the VW Beetle has a tendency to melt or it just start to burn. It's a very well known problem and is also really common. It the  main reason that so many Beetles have burnt to a crisp. The Beetle wiring harness running between turn signals / headlights and the ECM is also troublesome -intermittent. The wiring harness resistance between the injector and the ECM changes over time from 1 ohm to above 30 ohms. The wiring harness resistance between the alternator and the battery also increases due to failing fans thus causing excessive current draw resulting in the wiring harness  over heating then melt.

I've seen VW Polo and VW Passt headlight wiring harness melt. The connectors tend to melt due to the type of plastic used and can be traced back to either arcing / overheating of the the bulbs or shorting out of deteriorated wiring. VW Passat coil pack wiring harness also prevents the car from starting and when water enters the wiring harness in the cowl area beneath the windshield,  it caused a short that normally damaged / corrodes the electronic control module. 

Both the Volkswagen CC and the Golf Mk5 GTI now seem to have throttle body wiring harness issues causing the EPC light to switch on and make the car go into limp mode. But there is no fault code that tells you the wiring harness is faulty or intermittent. Another VW CC harness problem to be on the lookout for, is the trunk lid harness that physically breaks over time  due to opening and closing of the trunk. A common problem on VW Pasat is the ignition wires that breaks inside its insulation, resulting in misfires.  VW sells a six pin throttle body sensor connector kit with yellow wires (below) that needs to be spliced onto the wiring harness to circumvent EPC issues when presented with wiring harness / G187 & G188 DTC errors.

Throttle body rewiring kit

Audi throttle body connector kit.  The wires kinda looks like single mode optical fibre cables along with  fusion splice protection sleeves

VW also sells a  six pin accelerator pedal  connector (below) that needs to be replaced as a solution to EPC problems when presented with wiring harness and G79 & G185 DTC errors. There is a likelyhood that this culture of poor quality wiring harnesses has spilled over into all the other VW models as well. To make matters worse, the newest mania among vehicle makers like Honda, Subaru and Toyota  for example,  are to use eco-friendly soy-based insulation wire for their engine wiring harnesses. VW's, Audi and Porsche, uses a soy based wire sheath to encase the engine harness. 

The six pin throttle pedal connector the goes intermittent causing EPC problems.

As a result, rats and squirrels are attracted by the aroma of the wiring harness and nibbles off the tasty insulation causing the bare wires to short out. Apparently these soy-based wire coverings are totally irresistible to rodents. As proof to this, several VW owners who have had electrical problems with their cars have vacuumed rats nests along with dog food chunk from their engine compartments. Others have removed several hands full of hazel nuts shells from their air filter boxes  that squirrels made their haven.  

Replacement six pin connectors for VW Audi SEAT and SKODA

Be that as it may, modern day car soy based car components are not a first, during World War II, some U.S. states used soybean fiberboard for their license plates, which proved extremely popular among goats that made a feast out of them. All I can say is, that VW service centers are going to make a small killing by replacing wiring harnesses of the millions of VW on the road today. Personally, I think you whole biodegradable "go green thing" , "eco this eco that" is overrated and is  getting out of hand. 

Some time back, some Dummkopf  -Dr. Dieter Zetsche- at Mercedes Benz decided that all Mercedes Benz cars manufactured during 1992 – 1996 should be fitted with biodegradable wiring. This leap toward eco friendliness by Mercedes Benz was well-intended but those wiring harness prematurely disintegrated due to engine heat and caused untold electrical problems. VW should in fact take a lesson out of the Mercedes Benz's annals.

See the cracks and the brittleness of the wire insulation after just a few ears of use

However, there is a DIY remedy for biodegradable, rodent enticing soy flavoured wiring harnesses.  Honda Acura Acura supplies a genuine-OEM rodent-deterrent duct tape, which is treated with capsaicin, - super-spicy red-hot chili pepper compound - that deters rodent.  Wrapping you VW wiring harness before rats discover your car is the way to go. Enough said, so let me return the subject at hand. 

Spicy anti rodent insulation tape,

In the not too distant past, Volkswagen Jetta models manufactured between  January of  2005 and January  of 2006 were sold with a "defective door wiring harnesses". It wasn't that the harness was defectives in the sense of not working but rather the harness was made too short. As a result, thousands of Jetta owners were experiencing similar problems as the harness started to chafe and disintegrate through regular use.

Common experiences included loss of power to the door controls, failure of the power window controls, failure of the power mirror controls, failure of the fuel tank latch release, failure of the boot lid release. Other weird experience included loss of audio to the speakers, a tripped air bag light on dashboard, when locking the door with the key fob remote the radio to turn on, or the key fobs just doesn't work, also having to recharged the battery continually because it runs down overnight. The interior door-open lights wouldn't turn off  and neither would the buzzer, the sunroof opened randomly. The turn signal in the side mirror stopped flashing and neither would the hooter work but would beep at odd times when you least expect it.  The windshield wipers worked occasionally and the car alarm would trigger unexpectedly and repeatedly.

In fact most VW Jetta owners complained about loss of some or all of the controls located on the driver's door.  These  faults weren't confined to the driver's door, because it was purely a matter of time before the the passenger door also developed a short or an open circuit in  one or more of its electrical circuit. The only way to remedy the problem was to replace the  broken harness with a genuine VW replacement which turned out to be some 80 mm longer than those fitted in the Jettas doors.

VW Jetta Front door replacement harness

A class action suit was leveled against Volkswagen alleging that they knew the door wiring harnesses were deliberately  made too short at the time these Jettas were sold. It was further alleged that Volkswagen shortened the harness by 80mm was  so that they could save costs, which  would ultimately lead to premature breaking of the door wiring harnesses boosting replacement harness sales.

However, most other Volkswagens electrical problems can possibly be traced back to a a troublesome ground. Water somehow enters the ground wires, in the cowling below the windscreen traveling inside the wire insulation resulting in corrosion. Always check the ground connections located  under the battery tray, or ground connections underneath the air cleaner box, or located inside the windshield wiper cowling or in the engine compartment, or the ground connections on the steering column or behind instrument cluster.   Covering the ground connections with battery terminal grease should offset the corrosion, if any, Remember poor ground connections, can cause a multitude of problems if it they become loose, can cause anything from cam sensor codes, to instrument cluster problems like erratic speedometer display, to misbehaving fuel gauge, to a dead gear indicator light, to non operational windshield wiper,  to a flickering digital clock , etc. 

Volkswagens that are equipped with air conditioning  are subject to high ambient temperatures which often causes the battery to get drained whenever the radiator fan kicks in at full speed with the ignition shut off.  Under high heat conditions, the gas pressure of the refrigerant can activate the A/C high pressure switch, triggering the high speed radiator fan relay to activate the cooling fan. Volkswagen has subsequently recommended a replacement fan relay switch with other minor modification of the A/C high pressure switch wiring, to solve this problem.

Replacement Radiator fan control switch

Whenever your VW misbehaves and you cannot put your finger on it, the best thing to  do is to investigate every ground lug on every bit of the engine wiring harness that you can get at. Loosen it, cleaned it with a  wire brush and some emery cloth and if needs be replace ground lugs that are corroded and possible even the screw/ nut. Don't forget to retorque the nut to the requisite tension. It may even be beneficial to add a second heavy duty ground strap to decrease resistance if any. Heavy duty welding cable from a welders supply store is far more  tolerant to vibration than your average cheap jumper cable wire. Starting difficulties can often be traced / associated to a poor ground connection. 

Remember when repairing wiring harnesses that soldering is not the recommended nor the appropriate method of repairing  it.  Solder joints are not flexible and tend to break after  while due to vibration.  Always use insulated crimp lugs and bullets like these below on connecting terminals especially at ground distribution points.

Lugs, bullet and spade connectors for repairing ground connections.

There is a tendency among car manufacturers to  miniaturize the physical size of electrical connector contacts and thereby the oversize of the connector. The problem is that the surface area of contact is remarkably reduced and are thus prone to intermittent contact under vibration. This has now become very evident on the wiring loom connectors that interface with the throttle body and the accelerator pedal to the point that they need to be replaced when they go intermittent. Don't bother to spray them with contact spray, just replace them. they are cheap enough to buy rather than suffer constant EPC issues and they are even available on Amazon, ebay, DHgate, and other online auction.

@DomLittlewood I need your help on a case I have with Volkswagen. A Brand new Volkswagen Polo numerous electrical problems & now caught fire

— Deano Luke (@95deanluke) August 30, 2016