I have high beams and parking lights but no low beams, help checked fuses and relays check ok, last night no lights but kept working the switch and they finally came on, turned car off low beams never came back on please help!!
Try spraying the switch with electrical cleaner, might just be dirty contacts. Assuming the bulbs are good on the low beam.
headlight logic module
I’ll try both items thank y’all
Electrical cleaner can destroy plastic parts.
No way to actually test it on another part since that might be a different compound.
First I have heard of that, seeing as a lot of switches are plastic based I’d be surprised if that was to happen.
Gourgen is 99% correct on this. It is a common problem. Find a new replacement module, since any used part will be days away from failing as well, since they would also be 25 years old.
I’ve never had an issue with electrical contact cleaner with plastic, ever.
I usually start with a light solvent like Etoh.
The other good option is WD-40.
If it was actually wet inside then WD-40 might be a start but it is fundamentally not a cleaner, and not a lubricant. It will dry out and leave a residue that will gum up the innards of a switch.
David,
Your schematic is for the pre-facelift XJ-S. I believe that the face-lift cars, like the 1995 being discussed here, have a very different arrangement. It seems from the posts that I have seen on this list for the past 15 years that the face-lift cars are different than the earlier cars in most every way imaginable. 
Paul
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Here’s the early facelift (1992) schematic.
If you have checked the fuses and wiring then the culprit is most likely the switch or the control unit. You should be able to check the switch with a basic multi-meter. Although the control unit looks like just a couple of relays, it has some electronic parts inside so that it acts like a flip-flop. When mine went bad, one of the transistors had burned out so it would switch the relay from dipped to main, but not latch. It seems like you have a slightly different problem in that the relays are always energised to switch to high. If it isn’t the switch then it is worth a look inside the control unit to see if you can spot a burnt resistor, leaky capacitor, or a bad transistor. It’s a fairly simple circuit to repair.
If you want the electrical diagram for your 95, go to jagrepair.com
If you want to fix your problem, replace DAC6902
If you are an electrical whiz, perhaps you can repair your DAC6902, but in the end, that’s your problem.
My low beams went out about 1 week apart last month. I ended up removing the bulbs in the headlights and both bulbs’ elements were simply burned out. Replaced both bulbs and now are both back to normal. It could be that.
His went out at the same time, and after a number of tries with the stalk, they both came back on. So the bulbs work.
If one light doesn’t come on, that’s a completely separate line of thinking.
DAC6902
Understood, I may have missed that part. If they went out at same time, yeah that would be something in common that both lights have. Makes perfect sense.
Yep, Superblue’s module does the same thing, occasionally. Odd that she never just loses low beam while low beam is on, just when you go to transition from high to low she goes black. Sometimes if you keep on driving (CAREFULLY) they will suddenly pop on, or after turning a sharp corner. 
The way to get them working again for sure is to pop the hood and tap the module with your hand until they come on. Funny thing is I temporarily put Superblack’s module in her and IT acted up. 
I guess those things just get blinky after awhile. ?
Unfortunately, I don’t think I’ve ever found a NEW one. Are they even still available? 
I think I saw a post long ago that advised softening the black RTV-like gunk in the one end (maybe use a heat gun?) and slide the insides out. Probably a loose connection to a component on the circuit board or cracked solder that needs repair.
Another possible issue is, IIRC, the facelifts like ours have a separate relay for high beams and for low beams, and somehow they work in conjunction with the headlight module. Might try replacing the low beam relay and see if that does anything … I’m thinking of using that same approach with Superblue next time I get a spare relay. Really odd “coincidence” that all three modules (I also had an old used one that I bought sometime back) act up the same way when installed on Superblue. 
If it’s dark enough out, next thing that happens is you hit a tree. I’ve had headlights go off while driving at night for a couple different reasons, and it’s terrifying. Can you switch right back to high beams?
Can you swap the relays between high and low beams? If the problem swapped with it, you’d know you have a bad relay.
They are available new.