[anoop_lamba]

Hello all. We keep hearing about incidents where automobiles catch fire and mostly faulty wiring is blamed. When OEMs design wiring harnesses, they take utmost care in making sure that mechanical as well as electrical design of the wiring harness is such that chances of having any thermal incidents on a vehicle are minimised.

1. Mechanical : Wiring harness is laid out and covered with suitable protectors in such a way that wires do not get damaged due to sharp edges, vibrations, tension etc.
2. Electrical : Fuse selections, wire size selection etc are carefully done to ensure in wires don’t get overheated in normal or short circuit conditions

Problem usually arises once an automobile reaches the market and electrical accessories are put on the vehicles without taking care about the basics of wiring harness routing and connections. This poses a serious threat and can lead to thermal incidents. I am mentioning some basic checkpoints below that one must ensure during the fitment of accessories that requires dealing with vehicle wiring. Hopefully you will find it useful.

1. Fuses : Make sure that if a wire requires electrical power, a proper fuse is added to it. If supply is tapped directly from the battery, make sure fuse is put as close to the battery as possible (e.g. not more than 70-80 mm from the battery). This minimises unprotected wiring length.

2. Using existing fuses : Avoid taking tappings from wires of fuse other than the fuse designates for Accessories. For example, if a lamp fuse wire is tapped for an accessory and a fault occurs in the accessory system, lamp fuse will blow and you will loose critical lamp funtion because of your accessry system.

3. Tapping a wire : Never ever allow a simple stripping, twisting together and taping of wires. There are hardware and joint crimps available in the market for making a proper joint.

4. Use of Relays : Relays should be used where you want to drive a high power device (accessory) using an OEM switch or any switch which may not be able to handle that large current. Ensure your add on system included relays if it is high power and an OEM switch operated.

5. Grounding / Earthing : If the ground wire of the accessory is added to an existing gorunding bolt, make sure that it is tightened properly. If loose, current flowing thorugh it will cause the area to overheat.

6. Routing / Lay out : There should be no sharp edges along the wire route, if unavoidable plastic protectors to be used. Many accessories require wires to be taken from cabin area to engine area across the firewall. Unauthorised dealers usually squeeze the OEM harness grommet to make way for additional wires. This pinches the wires between grommet and sheet metal creating a high risk situation.

7. Fixing the harness : Add on harness should not be left loose or hanging. It should be fixed along its length to the (nearest) OEM harness using tie-bands etc.

Many of the authorised dealers also do not follow these leave alone the roadside unauthorised shops. I think its one time headache that we make sure wiring is done propoerly to make our journeys safer for us and our beloved ones.

Hopefully you will find this useful.

[sumeshmani]

These are some very useful tips. Thanks Anoop .
A friend of mine bought Volkswagen Polo (base variant). He got his music system fitted last weekend. They used a Volkswagen kit, for the wiring and harnessing.
Do most of the manufacturers supply such wiring kits or at least provide specification for the kind of wires to use, harnessing details etc?
If there are no guidelines, then it might be tough for third party vendors to approach each brand of car in an appropriate technical manner.

[jalsa777]

These are excellent tips. Thanks a lot.

Adding some more:

• Please select the wire gauge depending on the current requirement of your load (Accessory). Most incidents happen due to current over-draw.
• DO NOT cut the the wiring harness shielding. If needed, use supplementary wires from the battery, fuse box, etc.
• DO NOT tamper with OEM switches. Don't add load of extra light's etc. on the OEM switches. Use separate switches for the same.

[mayankk]

Oh this was needed.
Now tell one more thing.
In most fuseboxes, you have a few empty slots.
Do these carry power?
and is it okay to draw current from them?

[anoop_lamba]

Originally Posted by sumeshmani

These are some very useful tips. Thanks Anoop .
A friend of mine bought Volkswagen Polo (base variant). He got his music system fitted last weekend. They used a Volkswagen kit, for the wiring and harnessing.
Do most of the manufacturers supply such wiring kits or at least provide specification for the kind of wires to use, harnessing details etc?
If there are no guidelines, then it might be tough for third party vendors to approach each brand of car in an appropriate technical manner.

@ Sumesh : Yes. OEMs include properly designed add-on wiring harnesses in accessory kits. So if you buy an OEM kit, you can be rest assured that electrical part of the design is taken care of (no need to worry about fuses, relays etc). This is more than sufficient to justify that we should go for OEM kits. The kits include proper protectors, tie-bands etc for proper routing but at times technicians at dealer end may ignore those (who does not love short-cuts?). So it needs to be seen that layouting has been done properly (or atleast that they are using all hardware that were part of the kit).

Originally Posted by jalsa777

These are excellent tips. Thanks a lot.

Adding some more:

• Please select the wire gauge depending on the current requirement of your load (Accessory). Most incidents happen due to current over-draw.
• DO NOT cut the the wiring harness shielding. If needed, use supplementary wires from the battery, fuse box, etc.
• DO NOT tamper with OEM switches. Don't add load of extra light's etc. on the OEM switches. Use separate switches for the same.

@Jalsa : Thanks for including these points. Generally accessory kits use wires of 0.5 sq mm to 1.0 sq mm which can safely carry 8 Amps to 14 Amps of current (respectively). Thus using them power of 100W to 170W can be carried which is much more than sufficient for typical accessories.

Originally Posted by mayankk

Oh this was needed.
Now tell one more thing.
In most fuseboxes, you have a few empty slots.
Do these carry power?
and is it okay to draw current from them?

@Mayank : It may or may not. There is a simple way to check that. Take a spare fuse and put it in the empty slot. If it remains loose, there are no wires coming to that slot. If the fuse is gripped, it means Input side wire for the fuse is there in the slot and if we want to use it we need to add output side terminal and wires.
BTW there are cases where OEMs give empty slots with both wires and a connector for common after sales accessory kits like security system, power windows etc (may vary from OEM to OEM). All OEMs give fuse and connector for Stereo at least.

[neel385]

Very nice thread Anoop.
Electrical safety is not very high in many of our lists of safety checks and so, for me at least, this has been quite an eyeopener.

[jaygeetee]

Anoop, Very nice thread.
I realised this problem when I went for a ICE upgrade. The guy wouldn't use the different connectors etc. that was available. He said that it would cause problems.
I am waiting to get the whole wiring re-done by a better installer.

[born2drive]

Very very useful tips. I should have thought about this before fitting a new horn in my i10. Some portion of the wires got burnt and luckily i noticed it soon enough to avoid any more issues.

[samarth.bhatia]

Hi,

Thanks, Anoop, for the useful knowledge.
I am quite fond of getting accessories put up on the car.
Now I have serious doubts on the safety aspect of the wiring has been put up for some of these accessories.

I have been trying to ensure that crimps are used instead of cutting the OEM wires at most points. Until recently. Where I observed that when installing the Rear View Camera and sensors, the installer did make a joint by removing the plastic cover of the wire for the reversing light.
I tried saying that a crimp would be safer, but he told me they are more unsafe as crimps cut through the OEM wire completely!

Moreover, there are some wire for extra LEDs hanging around in the engine bay.

Can somebody please highlight where I can go (in Delhi) to get these problems rectified?

TIA.
Cheers and Drive Safe.
Sam

[mayankk]

Originally Posted by samarth.bhatia

Hi,

Thanks, Anoop, for the useful knowledge.
I am quite fond of getting accessories put up on the car.
Now I have serious doubts on the safety aspect of the wiring has been put up for some of these accessories.

I have been trying to ensure that crimps are used instead of cutting the OEM wires at most points. Until recently. Where I observed that when installing the Rear View Camera and sensors, the installer did make a joint by removing the plastic cover of the wire for the reversing light.
I tried saying that a crimp would be safer, but he told me they are more unsafe as crimps cut through the OEM wire completely!

Moreover, there are some wire for extra LEDs hanging around in the engine bay.

Can somebody please highlight where I can go (in Delhi) to get these problems rectified?

TIA.
Cheers and Drive Safe.
Sam

I did this.
stick with me.
Mseal.
Yes, we are all averse to sticking it to the car itself.
but try this.
get those black hairpins women use.
one is a proper thick one, which had no gap between the prongs, and ones are which are U shaped, and have about half a centimetre gap.
know the ones i am talking about?

roll a small ball of mseal around your wire where you want it to be mounted(be careful that you measure and choose this spot, cos its not going to shift, the mseal.
put the ball around the wire, and pass the hairpin through(the gapped one)

Now you can wait for it to dry, and wind the hairpin around a mounting point.
its easily snippable also.
you could also get thicker wire, but i found the pins to be most convenient, and easily available around the house....

use mseal phataphat, if the black one looks to utilatarian.

[superutp]

Thanks a lot for this topic & post anoop.
I recently got 'el-cheapo' DRLs fitted on my Beat, through an unknown accessories guy. Being a noobie and unaware of car electricals, I let him fit it (however, strictly told him not to disturb OEM wiring).
Turns out (I think!) he stripped and tapped one wire to the right indicator wire and took one more through the firewall and connected it my Autocop control unit above the glovebox. I have no idea about what the guy did, however insisted that what he did was correct. Even used the same source (the Autocop unit) for connecting LED sill plates.
Since that day there has been a slight buzzing sound (lasts 5-10 sec) coming from somewhere, whenever I switch on ignition and also sometimes from I brake to standstill (weird). Any thoughts anyone?
I am anyways planning on getting those crappy DRL's out and getting better ones fixed at a better place.

As said before, electrical safety is one thing we often overlook, no longer though!

[devsoftech]

Common Installs:

1. 90/100W "aftermarket" headlight relay kit - budget 900-1400. Please purchase a wiring kit that comes with 2 independent fuses for high and low beam (when you are drive in low beam and u flash, both bulb filaments will glow). The wiring leads should not require any cutting/splicing and should be bolted to the terminals. A cable-tie should be used to attach the wiring with the chassis and it is better to pass the wiring through front grille section all the way till headlamps. The wiring should be cased in a goose-neck plastic sheath for extra safety (some wiring kits come with it - go for those). Also, as the headlamps relay switching is triggered from OEM sockets, it must be insulated properly to avoid water/dust entry. Review wiring health every 3 months. At any cost do not run/tie with wire with sensor wiring's or near engine assembly. The relay kit is placed near the battery area and negative lead is usually screwed with the body.

2. Audio Installs - Invest in high quality wiring, fused as suggested in post#1. Also ensure that the wire's sheath is not compromised (susceptible to cuts) near door hinges, should you need to run new wiring for door speaker. (as manufacturers use rubber cladded adapters to organize wiring at door panels. installer "find gaps" and run these extra wires.

3. HID lamps - These kits can be very unprofessional, please avoid any cost cutting and do bear any extra costs for additional harness, adapters and leads

4. Power windows relay kit / roll-up module - A nasty install can be rattling, and also a risk to array of wires/controls on driver's door. Watch out for how the "negative" terminal power is harnessed.

[phamilyman]

Let me ask a different question - can we make a list of reputed auto elec mechs from whom we can get an audit done after all is installed? A.S.S mechanics are typically never good enough for this purpose.

[anoop_lamba]

Thanks everyone for your encouraging feedback on the thread. This was my first after joining recently a few days ago. Feels good to see that fellow BHPians could find it useful.

Originally Posted by mayankk

I did this.
stick with me.
Mseal.
Yes, we are all averse to sticking it to the car itself.
but try this.
get those black hairpins women use.
one is a proper thick one, which had no gap between the prongs, and ones are which are U shaped, and have about half a centimetre gap.
know the ones i am talking about?

roll a small ball of mseal around your wire where you want it to be mounted(be careful that you measure and choose this spot, cos its not going to shift, the mseal.
put the ball around the wire, and pass the hairpin through(the gapped one)

Now you can wait for it to dry, and wind the hairpin around a mounting point.
its easily snippable also.
you could also get thicker wire, but i found the pins to be most convenient, and easily available around the house....

use mseal phataphat, if the black one looks to utilatarian.

@ Mayank : That is quite an unique engineering solution. I would say it is still much better than loose hanging wires prone to rubs and cuts. One can use elec PVC tapes also to attach the add on loose wires to nearest OEM harnesses in the area.

Originally Posted by superutp

Thanks a lot for this topic & post anoop.
I recently got 'el-cheapo' DRLs fitted on my Beat, through an unknown accessories guy. Being a noobie and unaware of car electricals, I let him fit it (however, strictly told him not to disturb OEM wiring).
Turns out (I think!) he stripped and tapped one wire to the right indicator wire and took one more through the firewall and connected it my Autocop control unit above the glovebox. I have no idea about what the guy did, however insisted that what he did was correct. Even used the same source (the Autocop unit) for connecting LED sill plates.
Since that day there has been a slight buzzing sound (lasts 5-10 sec) coming from somewhere, whenever I switch on ignition and also sometimes from I brake to standstill (weird). Any thoughts anyone?
I am anyways planning on getting those crappy DRL's out and getting better ones fixed at a better place.

As said before, electrical safety is one thing we often overlook, no longer though!

@superutp: Thanks for for appreciation. It would be very difficult to guess the reason of the buzzing sound. Best would be to recheck if the problem persists after removing the DRLs.
Again an additional checkpoint for you. When you get the DRLs removed, make sure its not just the LED packs that are removed. All the related added wires should be removed from start to end. Many times if you get something removed, guys doing the job remove the main units and tape down relevent wires. In your case when you are not sure if wiring was done properly, make sure it also gets removed.
All the best.

[IndigoXLGrandDi]

Originally Posted by devsoftech

Common Installs:

1. 90/100W "aftermarket" headlight relay kit - budget 900-1400. Please purchase a wiring kit that comes with 2 independent fuses for high and low beam (when you are drive in low beam and u flash, both bulb filaments will glow).

Our Xylo E8 ABS has two separate fuses (OEM - came with the car) for High and Low Headlight Beams.
But when I drive in low beam and I flash, only the High Beam filament glows.

Any idea on this?