fog lights not working

Hi all, firstly I am a "total NOVICE" when it comes to auto electrics, as you will soon see and am hopeful that someone can shed some light on the problem with my fog lights. 

I have a 1999 Dodge Ram 1500 Extended Cab P/U with factory installed fog lights.  A few months ago I added a set of Hella (500's I think) to the truck and had them wired into the existing fog light wires, and they worked fine up until about a month ago.  At that point neither the factory OR Hella fog lights would come on when the fog light switch (apart of the light switch on the 99 Ram 1500) was pulled to the on position.  As such, I checked all of the fuses (both under the hood and on the dash board) as well as changing the Fog Light Relay without any success.  I had all of the fuses etc checked by a body shop who confirmed that all appeared okay.

I then disconnected the Hella's leaving only the factory fogs connected as they originally were and still had no lights.  I then changed the light switch and switch harness, again, without success.  I then tried just connecting the Hella's to the factory wiring and still got no results.  I then ran a wire from the Hellas to the positive and another to the negetive of the battery and established that both lights worked fine, in other words, it isn't something as stupid as blown globes.

Okay, so the last thing I did was cut the factory wires disconnecting them from the lights themselves and checked whether or not I had power in either wire.  I have two wires (factory ones) one blue and one red.  When the wires were NOT connected to anything, I had power at the red wire and nothing in the blue wire.  That to me indicated the Red wire was the positive and the blue was the negetive or ground or earth and was as they should have been - power in one and no power in the other.  I again reconnected the factory lights (blue to blue and red to red) and still no lights would come on.

I checked power to the lights again and established that I now had power in BOTH the red and blue wires???  That to me doesn't sound right at all, or does it ?

I think I have checked and/or replaced everything I an think of regarding the lights and still have nothing.  I hope my explaination of the problem is clear or clear enough for someone who knows what they are doing (unlike me) to offer a solution or some suggestions as to where I can look for the problem next.

Thanks in advance and sorry for the very novice post. 

Cheers,

Womabt457

Sounds like you have no ground. The red wire sounds like the power wire, the blue sounds like the ground. Your bulb is a resistive load so when you apply power to one side of it but leave the other side "floating" you will read the voltage across the load (ie you will read voltage on the ground wire). OEM circuits are NOT designed to be tapped in to the way you did. Your aftermarket foglights should have their own dedicated feed fused from the battery and their own dedicated ground. A relay should be used to switch them on and off and that relay can be triggered by the OEM foglights if you want to use the same switch. Best case scenario your splice in to the ground has failed, worst case scenario the added load has melted the wiring.Kevin Pierson

KPierson wrote: Sounds like you have no ground. The red wire sounds like the power wire, the blue sounds like the ground. Your bulb is a resistive load so when you apply power to one side of it but leave the other side "floating" you will read the voltage across the load (ie you will read voltage on the ground wire). OEM circuits are NOT designed to be tapped in to the way you did. Your aftermarket foglights should have their own dedicated feed fused from the battery and their own dedicated ground. A relay should be used to switch them on and off and that relay can be triggered by the OEM foglights if you want to use the same switch. Best case scenario your splice in to the ground has failed, worst case scenario the added load has melted the wiring.

KPierson Thank you for your reply, glad you understood my "garb" I confess the ONLY thing I didn't do was to reconnect the factory fogs back to the factory wiring to see if they worked separate to the Hella's. I will do that as soon as the weather warms a little. If that does work, and from what you have said, there seems to be no reason it won't, then I need to install the Hella's with their own wiring and to their own switch, which isn't a problem for me. I don't care if the fogs come on with the low beam lights or not I just want/need fog lights. Thanks again for the help, it is appreciated.Cheers,

Womabt457

Hi Guys - I finally got around to completely disconnecting both the factory and after market lights and started again. This time I hooked up the Hellas on their own Relay, switch etc and they now work fine. The factory lights still do not work though and, as KPeirson wrote, it does appear to be a faulty Ground some where. Trying to find that problem is another adventure. Perhaps I will by pass the factory wiring and do the same with those lights as I have with the Hella's! Thanks to all who gave advice. As a result, I now at least have some lights - and that is VERY much appreciated! Cheers, WombatCheers,

Womabt457