When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was attempting to brighten up things a bit with LED bulbs in the interior lights and puddle lamps in my '05 Expedition. But, it seems to have introduced a parasitic draw on my battery, this morning it was cranking quite slow, but started. I've now pulled the bulbs and I'm going to put normal bulbs back in there, but I'm wondering, why does this happen? I've looked at the wiring diagram, and as far as I can see, it must be something to do with the output from the instrument cluster for the slow on/slow dim feature which doesn't like to have LED bulbs connected to it, as the LEDs do have some sort of circuitry in there... Anyone else tried this?
LEDs will not cause a parasitic draw. Even if they have circuitry in them a regular bulb is also a constant load as well. Check to make sure your glove box and under hood lamps are going out. Also keep in mind the interior light relay kills power after 40 minutes, so the likelihood of any interior light being the cause of the draw is slim to none.
I know, and find this puzzling myself, but it has been perfect with no parasitic draw before, and the only thing I changed was the bulbs. Ive now removed the bulbs and will see if it still does it or not, too early to say yet, but if it does not occur now then it has to be something going on with the dimmer circuit..
Did a quick check just now, seems I have a 500 mA draw when ignition is off, and just connecting the probes. Not sure how long it takes for stuff to "go to sleep" after battery is connected, but it started pouring down so I had to just leave it with the battery unhooked.. Now I wonder, could the LED's have damaged something, like the dimmer circuit or something in the instrument cluster, causing a parasitic draw? I'll have to check it properly tomorrow in daylight and hopefully without rain.. Really weird this appeared just after replacing those bulbs, but it may just be a coincidence as well, I don't know... Glove box light is off and I don't have any under hood light so nothing else could cause any draw as far as I'm aware. Everything on the truck is factory stock, LEDs is the first real "addon" I've attempted actually...
Well, that was an expensive lesson...... I have no idea how it could happen, but the LED's seems to have damaged the dimming interior light circuit in the instrument cluster. Pulling fuse 21 renders interior lights inop and removes the 480-ish mA draw and takes it down to 10-15 mA, which is well within specs... So, I'm now attempting to open the IC and find out if it's repairable, if not, I'll be shopping for a new one on ebay... Note to self: Don't mess with LEDs! lol..
Seems like the circuit is designed in such a way that it cannot handle a capacitive load, which many LED bulbs with active circuits do represent.. It can only handle a resistive load. This means that anyone attempting this must be extremely cautious about the type of LED bulb they buy. It wouldn't affect a relay operated circuit, but at least on the '05 the instrument cluster uses a solid state voltage regulator circuit to enable the soft on/soft off feature. I will attempt to replace the components which seems to be connected to the output for the interior lights, but I have to order them in. I'll post back once I have replaced them if it solved the problem or not. If not, then it means that it's necessary to replace the instrument cluster in order to fix this problem... All this for some stupid LEDs, lol...
Seems like the circuit is designed in such a way that it cannot handle a capacitive load, which many LED bulbs with active circuits do represent.. It can only handle a resistive load.
Well, interesting update. I may have been chasing the wrong squirrel..
After going through the PCB in the instrument cluster again, I am not able to pinpoint any faulty component which is able to handle the power needed to switch the 40-odd watts of bulbs, so I began suspecting that something might be backfeeding the circuit and then create some sort of power draw through the switching circuitry. I installed the instrument cluster back into the truck and pulled the connector marked C238 on this diagram:
and battery drain went from around 480 mA to 45-50 mA. Still on upper limit, but acceptable and within spec. I've pulled all the interior light sockets, no change, so I'm suspecting the puddle lights. Will have to remove the door panels and disconnect them, but no time today... If this is the case, then I suppose the issue was never the LEDs, but rather me disturbing crusty wiring and creating an issue that way..
More progress, in a process of elimination the fault has now been isolated to the instrument cluster. Disconnecting the previously mentioned connector must have removed power to parts of the instrument cluster and in that way reduce the power draw.. The pinout diagram for that particular connector just references circuit numbers, and I haven't cross referenced it yet (big connector). But, I took the connectors to the instrument cluster, removed the output pins to the interior lights from the instrument cluster, power drain was still there. I then removed the power supply pins for interior lights coming from the fuse box and supplying 12V constant power to the instrument cluster, and power draw disappeared. In other words, the only thing that draws an excessive amount of power on that circuit is the instrument cluster, and that power draw is there regardless if something is connected to the output or not. And the fault must then be internally in the instrument cluster. For now, I've temporary fixed the issue by pulling the fuse on that circuit, and I'll take time this weekend to once again check the PCB, and I'll thoroughly check the components that are able to handle a big load. My primary suspect would be the caps, so I'll start there and see if one of them traces to the outputs on the connector.
Why Ford designed the interior light circuit like this is really beyond me, not a smart move, specially when it seems to be very sensitive to what is connected to it. I'd think an external relay, perhaps a solid state one with a dimmer feature, would make much more sense as it would probably be more robust. Doing it like this, and then have people replace a whole otherwise fully functional 500-dollar instrument cluster is pure evil... lol..
No, i meant the C238, but when pulling pins as mentioned last, that was pins 1 and 14 for power supply and pins 16 and 17 for light output on C220a. I let tyem go to sleep with time, waiting about 15 mins or so. But the power drain disappears immediately when removing fuse 21, even if I just connect the battery, meaning its not the modules drawing power, its the instrument cluster on tyat particular circuit
Follow the circuit after the splice, don't you see the C238 above the letter B reference?
Glove box lamp is off, not drawing power. With fuse 21 in place, and removing pins 1 and 14 on connector C220a, the power draw goes from around 480 mA to around 15 mA, meaning that circuit is powered but instrument cluster is removed from that circuit.. If leaving pins 1 and 14 on C220a connected, but removing the output pins 16 and 17 on C220a, the power draw is still around 480 mA, meaning there's nothing connected in terms of lights or any load, but the instrument cluster is still internally drawing power.
The instrument cluster is controlling the battery saver relay yes, but that only handles the manual on/off button on the interior lights and has nothing to do with the auto on/off when opening doors, unlocking and so on.. Glove box light is a simple circuit, no control except the switch which turns it off when you close it.
11-21-2015, 09:59 AM
