ka24e -> ka24de harness issue

[s13mario]

so i recently swapped my s13 from sohc to dohc. Once i got everything wired up with the harness and ecu (i have the dual cam harness and ecu with sohc cluster)started up fine everything was getting power etc. ,no idle problem ,drove it around for a couple of days and now nothing gets power and the headlight switch cuts off the power to everything in the "on" position. I've checked all the grounds and i have no kill switch and have a new battery
NEED SOME ADVICE TO FIX IT

[centralcoaster33]

I'd get in there and check fuses and relays for things like ECCS, Accessory 1 and 2, etc.

[s13mario]

what incorrect wiring would cause the shorting if it ends up not being any fuses or relays

[centralcoaster33]

Are you using all of the plugs of the DOHC harness? Does that harness match the ECU you have? Do those match the DOHC engine? I mean are all three friends or did you get them piece meal? Pins could be different among them if their from different sources. Wait, scratch that. Your car ran fine for a few days. Let me think about it more.

[s13mario]

the harness and ecu are oem with the dohc motor
only thing i really had to mess with was the sohc cluster connector and adapt it to the dohc harness but the tac and speedo dont work but everything else did water temp ,fuel level ,.....but like i said it ran fine and then out of nowhere it didn't start anymore and the headlight switch made it all weird so thats where im stuck

[centralcoaster33]

I got nothin. Maybe you can pull fuses out of some non-engine related systems. Kind of turn them off temporarily. Then see if you can get the engine running again. As a process of elimination thing. Maybe pull those head light fuses or relays out and try the engine, then if that didn't work, pull some more out for interior stuff like AC or heater and such.

You could have had a loose connection, like a ground or a plug, and it finally came all the way loose. So, maybe you can at least go through all of the plugs on the engine harness and make sure they are connected nice and tight.

Do you have any check engine light type codes you can pull?

[s13mario]

will do
and no i dont , dont have and obd plug to put The scanner in
and since the cluster plug is different ,not really sure is the check engine light works

[centralcoaster33]

Hmmm, well, you can pull codes using the blinking light on the back of the ECU I believe. Here's a link to some instruction related to that. It should work with your ECU.
1991-1994-240sx-reading-computer-ecu-codes-t253912.html

[s13mario]

so I used the link to check for codes but its not throwing any
also for some reason it'll start only if introduced with and external power source like jumping it O_o don't know why
and i used a volt meter to check the fuses that control the headlights and motors etc ,and while the key is in the off position those fuses still have power running to them
would a bad alternator have anything to with it??

[centralcoaster33]

Hmmm, isn't that normal? I mean, I can take the key out of my 1995 240sx and my headlights would stay on. Now, it does ring a chime (bell, whatever) when I do that, to let me know I've left my lights on, the door is open and the key is out. That is a warning so I don't come back to find a dead battery. Anyway, the point is, I don't need a key to turn on my headlights, so I would guess you don't either.

No codes is okay, but I think you're supposed to get at least one code and that is the OK code, if everything is okay. Not getting that, well maybe the car needs to be driven more or something. I believe it is code 55.

Check the routing of your power cable sub-harness bits. The one that comes from the positive battery post, to your starter and such (plus alternator, maybe transmission, etc.). I forget what all is in that ball of wires, but check it all out and verify the connections.

I'd be thinking maybe some relay isn't working right, but I don't know at this point. You could swap a few of those around for testing purposes. ECCS relay, starter relay, accessories, fans, headlights, etc. Hell, I'd just get all swap happy and see what happens. I'm sorry I'm not much more help.

Oh, and BTW, a lot of this is all controlled by the ignition switch. It sort of tells a lot of those relays when to be on or available of off. Can you test that thing out or try a replacement or something?

[s13mario]

thanks man @centralcoaster33 you've been a big help dude
appreciate it
bad alternator and headlight relay and a ground to the fuse box in the engine bay was causing all this issue

[centralcoaster33]

You got it all, WIN!

Keep coming back, we've got lot's of neat thread topics, ideas and entertainment on Nico Forums (shameless plug). We're glad to have members like yourself that can DIY and think critically.