Hey everyone I have a 348ts that I'm having a turn signal problem with. With the headlights off both sides signals work normally, left is a little more dim. If I turn the headlights on, the left turn signal doesn't work at all, no click, no indicator, no bulb illumination. They work with the hazard switch (left a little more dim). It recently got a new turn and headlight switch assembly, I plugged the old switch in to confirm it is the same. My suspicion was bad ground, now that I've got to it, there is 1.5 ohms from the turn signal connector to ground. I dont think that's enough to really be my problem. I dont have access to wiring diagrams for it, is there something that connects the headlight and turn signal function? As always, thanks for your time!
I should add, I have found threads on here regarding the hazard module, although I cannot find that in the vehicle. In the left kick panel/knee bolster area there is a standard looking relay, and the acoustic module. Neither of which resemble the hazard module I saw in the other threads. Also this car has extensive aftermarket stereo. There's no room for a book in the luggage compartment. Joy.
I'm not sure what you mean by "turn signal connector". Here's the wiring schematic, but it may take a while to figure out. https://www.dropbox.com/t/LQ3CpsKVwrB1sMAx Link expires in 6 days. The Dropbox preview will take you to a PRINT button. Push this a couple of times and the page will allow you to convert it to a pdf file if that is your preference. The file may be best viewed on an iPad or similar device (easier panning and scrolling) At the moment, the only connection between the headlights and the turn lights I can see are the earths in the respective corners.
For info, the hazard/turn signal system uses 3 relays in the centre console (vertical section) in addition to the Hazard/Turn Module. For left/right turn indications (not hazard), the power going to the hazard turn module goes through the relaxed contacts of what I call the "power select" relay (208).
Thanks for a quick reply. At the turn signal assembly (maybe not the proper turn, see attached photo) there are 3 connectors. A 2 pin round, a 3 pin round, and a 2 pin flat. I was referring to the 2 pin round. The 2 pin flat appears to be a "jumper" coming out of the turn signal and going to the side repeater. It doesn't appear to be that way in the diagram, I see a 2 pin and a 3 pin in the diagram with the side repeater connected to the turn signal switch and the 2 pin connected to the fuse block. If i haven't lost you yet, if I disconnect the 3 pin round and 2 pin flat, the left turn signal indicator (on cluster) works as normal, headlights on or off. But flashes faster. Since I've done that, even connected, left turn always flashes faster, but still doesn't work with the headlights on. However the diagram you provided seems to show it wired separately if I'm understanding that correctly. I apologize for any confusion my north American understanding may cause. Image Unavailable, Please Login Image Unavailable, Please Login
I believe the relays are working, as the light is capable of flashing. It seems to me that when the headlights are on, the additional current load can no longer be supported. That's what made me initially suspicious of a ground. I had read another thread that mentioned 3 relays in the center, but I couldn't find those either, there is more aftermarket stereo garbage in there. I'm just a bit confused on what terminal or pin on each of the 3 connectors at the lamp assembly are supposed to perform what function. See attached photos of aftermarket stereo. Image Unavailable, Please Login Image Unavailable, Please Login
Image Unavailable, Please Login For info, they're on the back of the switch/display module. They are soldered in and, as far as I know, not available separately.... not that I'm saying that they have anything to do with the problem, but pray that they aren't (Apart from buying a new panel, the next best thing is hardwiring a remote relay to the back of the panel) Being a non-Euro car, I assume you have side markers, not turn repeaters. That undocumented plug may be a jumper for the sidelights (markers) on US cars. I have had earthing issues on my F355 which made all the tail lights flash, including the brake lights, so don't assume a flashing light is actually a turn light As you probably know, the turn light system is designed to flash the lights faster if a turn light bulb has blown. i.e. resistance changes cause the bulbs to flash faster. By disconnecting a plug, you are changing the resistance. You may get some expert advice on the 348/355 (particularly from our resident 348 expert, Miro, @m.stojanovic). I'm not sure where the earths are on the F438. On the F355, there is a major earth just next to the forward luggage compartment fuse/relay panel. I'm not sure I see it in your photo. Anyway, it shouldn't be too far away and the resistance of the wiring to it shouldn't be more than a few hundred milliohms at worst. Given your audio setup, I'd be making sure your earths were perfect.
Have you tried unplugging the other side and swapping the light units round (obviously you cant fit them back on the car) then you can verify that the problem is on the car electrical side and not in the light unit/bulbs etc I did this on mine when trying to diagnose a problem and it turned out my brand new light unit was faulty!!! :-(
I didn't read everything, but stopped at 1,5Ohm... If you have really 1,5Ohm in the ground thats way to much. with 1Amp you allready loose 1,5V! Better way is measuring the voltage loss in the ground cable with everything working: the current is high and so is the loss! Anothers quick trick is to put a temporaly ground cable on the point you suspect. The most common mistake in electric diagnoses is to figure out why a lot of systems dont function... better take the turn light and fix that (you will see it turns out that the other problems are solved to). Good luck!
Yeah I am familiar with the fast flash indicating a bulb out. When I first started on the vehicle left side flashed at the same speed as right, I have no determined there are two bulbs on each side that should flash with the turn signal, left side only has one working, I suspect the other bulb is out. Are the bulbs in the lamp assembly replaceable or is it sold as an assembly? The pin that I have the extra resistance to ground is in the 2 pin round. Wiring diagram shows neither pin in the 2 pin round as ground, is that correct? Before I had the diagram, I assumed the black wire in the 2 pin round was a ground.
Thats a great idea, I will pull the lights out and plug the right side light into the left side this evening and see the results. I've just never seen a burnt out bulb mean the signal doesn't click or anything only when the headlights are on. I can't quite make sense of that
Just check here from when I had probs with my lights (bulbs are replaceable BTW) https://www.clubscuderia.co.uk/forum/showthread.php?45388-348-DIY-quot-Restoration-quot&p=699846#post699846 scroll down a bit on link below https://www.clubscuderia.co.uk/forum/showthread.php?45388-348-DIY-quot-Restoration-quot&p=700847#post700847
Sorry, you've lost me on the plugs. If the wires on the plug are black and yellow/black, then, most likely, they would be associated with the sidelights (either the ones on the front or the ones on the side of the car). Since I'm not familiar with the routing of the 348 wires, you may need to go to the 348/355 forum to get an answer. Perhaps you were measuring the resistance of the side marker lamp, not the earth?
I apologize I know this has gotten confusing. But I think I'm starting to understand what's going on. The side marker lamp and turn signal lamp feed into the lamp housing via the 2 pin round, both those circuits ground through the 3 pin round. There is a jumper then from the lamp housing to the side marker. I think it is likely you are correct and I was not measuring resistance of a ground circuit. Sometimes the Ohmmeter gets me into trouble. I'll know more when I get back to it shortly.
Great. That seems to match the diagram. All the lights in that cluster use the 3 pin black wire as the ground. I'm not sure how that flat plug is wired in, though. I guess if you measured across the pins it would show side marker lamp resistance.
Something like this? Image Unavailable, Please Login ... or are the jumper wires on the other side of the plug (not on the lamp housing side)?
That is correct, just like that. I was certainly over complicating this. I did find a burnt bulb, but the new bulb has the same condition as well. I removed both housings and plugged them into their opposite sides, it then became the right signal that is inoperative. I tested resistance from the bulb sockets to the lamp housing connectors, all are 0.2-0.3 ohms. The only issue I can find with the left side lamp is one of the turn signal sockets ground terminal appears to have some melted plastic around it.
Sounds good. Because the fault transferred, I guess their must be a short in the housing between the wires with power on them and the earth wire on the housing, but that doesn't really explain why the headlamps are influencing the lights. Are your headlights (low and high beam) and daytime flashers operating normally? What happens when you have your headlights on and flash the high beams? Do your daytime flashers remain off? I guess lamp housings are not cheap.
I apologize I'm not sure what "daytime flashers" are. Headlights and high beams function correctly. There are 3 bulbs in the turn signal lamp housing, 2 amber, that work with the signals, and a bright white, I would call a fog light. I have now found and repaired the turn signal problem. The one socket ground terminal I previously said had some "melt", was not contacting the metal body of the socket. I cannot explain exactly why this caused the problem it did. After repairing the connection on the ground signal socket, all signals are working normally regardless of headlamp switch position. If there were a "short" between wires with power and ground, there would have to either be blown fuses or smoke. This was an open ground in a parallel circuit, increasing the resistance of the circuit. I believe.
When your headlights are not on and you pull back on the light stalk on the steering column, which light illuminates? This is the "daytime flasher". The Euro-based F348 wiring diagrams show 4 lamps in each front clusters. One of these is for daytime flashing. I'm not sure if the USA car is the same. For comparison, the USA F355 has a single lamp for front fog and daytime flashing. Anyway, thanks for the update.
