wig wag system problems

Hi, I am new to the forum, but have been reading the posts on here for quite some time... I wonder if anybody can help me, now and again I install lights and sirens on private ambulances, in the past I have had no problem at all, however I have come up against a new problem I have not seen before. It may be common in some vehicles, but I haven't seen it in the vehicles I have worked in in the past. Trying to install a wigwag system on the front and rear lights, the rears have to be on the fog lights/brake lights and the fronts need to be on the high beam. This has never proved to be a problem in the past and they are fairly easy to install, the car I am working with is a 2005 MG ZS, this car is registered as a private ambulance but has no wig wag on the lights, I have been asked to install on the rear and the front, now I have found out why it possibly wasn't done in the past...the lights, front and rear are switched on the ground wire. The ones I have done in the past are on the live power wire, which enabled a simple cut into the power wire to flash the lights on and off using the wigwag relay. As this system is switched on the ground wire I am not sure what to do. Does anyone have any ideas or if a modification is required to the wigwag system what I can do? I have attached a wiring diagram and instructions of the wigwag system if that helps anyone?

Cut the individual ground wires,if you use,trigger from 86+ rather than 85-

Or relay or transistor flip the outputs. BTW, I have a Rover 75, they are all POS, Jag S type and its brother the Lincoln Town car were NEG.

Thanks for that, so basically I need to open the case of the wig wag relay system up and connect the wire that is coming from the 86 terminal to the neg wires on the lights? Sorry if I sound stupid, don't want to do it wrong... I haven't dealt with many Rovers/MG's tbh. Usually the standard Volvo or Mercedes Sprinter.

Actually I would speak with the manufacturer, if not place the relays in series before or after the unit:- wig_wag.bmp In fact try it on the bench, I'll bet if you make the white neg, you will get blue neg out. That white to blue is just being switched, it doesn't trigger anything, neither is it connected to the internal circuitry, it's passive, just being switched.

You could fairly easily modify the vehicle to be + switched. You can use the existing (-) switched wire as a trigger for a relay, permanently ground the ground wire, and then cut and power the (+) wire with the relay.Kevin Pierson

Kevin, I'm sure polarity on that wire is irrelevant, it's simply being switched on and off, I think, if I'm wrong, my diagram covers it.

In fact 2 seconds on a bench with a power supply and a meter would give you or me the answer.