2007 Dodge Durango purchased new by Fire Department delivered in May 2007.

We added low volatage (LED) warning lights and radios after purchasing the vehicle. When making these connections we were very careful not to tap into anything that would cause problems for on-board computer.
I ran a single wire directly from battery to a cellenoid (used to activate all of the warning lights and radios) and picked up an ignition source from the OEM cigarette lighter circuit that was hot on ignition side (10 amp - fused).
There were absolutely no other connections made to the vehicles electrical system.
Just the hot lead from battery and the ignition wire from cigarette lighter that activates the Cellenoid when key is turned on.
After installing lights/radios I drove vehicle for over 3 weeks w/o problem, suddenly it would not start. Battery showing 13.2 volts, no fuses blown, everything came on... just would not start. Towed to Dealer-
Dealer clamining that by tapping into the cigarette lighter we toasted the on-board computer. They have now had vehicle over a week and I keep getting different stories, but bottom line is they remain firm the cause of the problem is this connection. They (dealer) has thus far toasted TWO boards trying to fix this and are charging me for both, and have now ordered a new board (which I also have to pay for).
I find it difficult to believe that tapping into the cigarette lighter circuit to activate a cellenoid would cause this. There is little draw on this, the fuse has not blown and all the wire does is turn the cellenoid on so the power (from battery) can operate the lights/radios.
I have asked the dealer where we can pick up a hot lead from ignition if I can't use the cigarette lighter, they claim that this cannot be done without screwing up the computer! Does this sound rationale to you?

Here are several thoughts:

I don't believe tying into the cigarette lighter circuit is ever a good idea, especially on OBD-I or OBD-II vehicles. I would create a new 7.5 A circuit, dedicated to the application, coming from an unused (extra) fuse slot in the under-dash fuse/relay box. The flow would be battery, under-hood fuse/relay box, ignition switch, under-dash fuse/relay box, solenoid, and so forth. This approach prevents you from affecting any other circuit in the vehicle. Since it would be coming through the starter switch signal, it should be properly recognized by the ECM and not cause a problem. This is the same approach you would want to follow, if you were adding a new room to your house. You would add a new circuit that ties into the main bus in the circuit breaker box, not tying into an existing circuit in an adjoining room.


It's possible a fuse did not blow, because you tied into a 10 A circuit. ECMs are often protected with 7.5 A fuses. Regardless, emergency vehicles demand first-class circuitry, not tying into cigarette lighter circuits where anything can happen. Cigarette lighter circuits frequently cause problems, which can affect readiness. On pre OBD-I vehicles, your solution would likely have worked without a problem. There may be fire department approved methods for wiring these type of devices on OBD-I and II vehicles. I would call around to other departments.

Even without studying the electrical diagram for your vehicle, I can see what the dealer says may well be true. When you tie into the cigarette lighter circuit, you are often tying directly into the charging system; i.e. voltage regulator and ECM. Your hookup is likely an unrecognized input to the ECM. The alternator control system within the ECM changes the voltage generated at the alternator in accordance with the driving conditions. Recognized inputs to the ECM are, for instance, Throttle Position Sensor, Engine Coolant Temperature Sensor, Intake Air Temperature Sensor, Starter Switch Signal, TDC/CKP/CYP Sensors, Vehicle Speed Sensor, Brake Switch Signal, ELD, and Air Conditioning Signal.

We are all so grateful for our fire fighters. I'm not trying to be critical of what you did but helpful.

I'm an old doit yourselfer
If tying into the lighter causes trouble, then why do we not get trouble when we plug in an accessory, what I suggest is that you check all sensors, see which is not working, and replace it, next suggestion is that you check all earth connections, especially the one to the alternator.make sure the bonding is intact.
You say the garage has screwed up other boards, surely they removed your wire feed, before they tried, and if they did then your wire feed, is not to blame.
May I suggest you try an other garage, one with a diagnostic machine
Joe