weird electrical issue in RX-3
 

Well I'm somewhat stumped on this one, so I thought I would run it by you guys.

so the other night I'm just crusing along at maybe 45-50mph in my RX-3, lights on with no accessories like radios, etc. All the sudden my headlights go SUPER bright, then go out. Nothing after that except parking lights. No brights or regulars.

So I limp it home and try to figure out wth happened. At first I'm thinking a fuse, check all of them and they're fine. Then I think maybe the headlight switch itself went bad. I'm fiddling around with the switch and do manage to get the brights working, but not the regulars.

Today I tested an old RX-2 switch (same thing) and it's not the switch.. turns out my alternator went haywire for some reason and blew out the regular part of the headlights, yet the brights will still work. weird? heh

I have noticed a few times that the voltage will spike up to 18v+ for no apparent reason, even at idle.. this will only last 5-10 seconds but still doesn't seem normal. I've also noticed the tone from the holley fuel pump in back changes from low to high when this happens.

So this evening I took out the alt. and had it tested at a local auto parts place, it passed fine. All I can come up with is either something is up with my wiring or that alternator has an intermittent spiking issue that didn't show up in the tests they ran.

The F terminal needs 12v when ignition is switched on, right? I don't think mine does right now, so perhaps that is my problem. Another odd thing is when you first start the car the alt. will not be charging, it will indicate maybe 10-12v. After you drive the car a bit and rev it up a few times the alt. suddenly kicks up to 13-14v like it should be the whole time really.

any ideas?

Thanks,
Mike

it could be the external voltage regulator located on the inside drivers side fender. just do like me and others did and upgrade to an internal regulated one.

It already is internal, the car has a 2nd gen. RX-7 70amp alternator. Sorry, forgot to mention that. I believe the problem might lie in the wiring. I don't think the previous owner jumped the old external regulator wires correctly, so the R terminal doesn't get 12v when the ignition is switched on. Either that, or the old regulator is still there and conflicting with the internal one. I don't remember seeing an external regular, still need to check it though.

Mike

i just wired up a friends rx3 so he could go to the apple blossum car show,, I put on a later internaly regulated alternator and used the the starter solenoid wire to trigger the field of the alt durring cranking cranking only. you have to use a diode to keep the alt from keeping the starter engaged,,,, I have used this method on my old rx3 race car and also on a repu. you can activate the field manually by just momentarly touching the right terminal to 12v while the engine is running,, I believe it is the L terminal,, the other one does not get hooked up at all. you can eliminate the external regulator too.,, Never hook up the field to constant power.
john from spokane,,,btw a nice diode to use is gm part number 12135037, it fits into a mini fuse holder

Now I'm lost, I swore I've read on here several times where people hooked up switched 12v to the field terminal. Why should you never hook it up to constant power? or do you mean constant vs. switched 12v? Never heard of the diode trick either.

Also, forgot to add that I've been running the above setup with the 2nd wire going to the gauge light on my RX-2 for over a year. No problems so far.

Mike

I'm no expert, but I think running constant power to the field will defeat the regulators purpose and overcharge the battery(over voltage). A momentary touch is all that is needed to energize the field and get it active. You never heard of the diode trick because that was my own invention to simplify the wireing in the old race car. Running the second wire to the gauge indicator lamp seems like the correct way to do it, but I didn't need that feature. I think it was designed to illuminate the check alt light when you first turned the key on so you could check your dash bulb and make sure that it was not burned out.

I have a question, I have I beleive a 100 amp altenator in my car from a later Cosmo now what wire do I use to turn off the Altenator light. I have to rev about 2500 rpm to get the car to charge. and with a built in regulator would it hurt anything if I leave the external regulator hooked up. By the way the car is a 74 Rx2 turbo with a haltech computer.

The light should go out once the alt. voltage is higher than the battery voltage, at least that's how mine works. It's the L terminal on my alternator.

Anyhow, I was talking to one of my neighbors last night and was describing the weird problems I was experiencing with the car. Immediately he said check the ground cables. I thought about it and that may be the actual cause as I believe there is possibly paint under the ground cables. I plan to remove them and clean eveything up, then see if it sill has the same symptoms.

Mike

I would check all the grounds, I am saying that because I have a haltech e6x and one of my main problems was grounding. I read with that computer their was alot of problems with noise so I made sure I had good grounds and my timing is rock solid.

Well I cleaned up the ground cables earlier.. there was a tiny bit of corrosion, but more importantly they were put on over the paint. I scraped some paint off under the bolt hole and reattached everything. So far it hasn't acted up, seems to run a bit smoother also.

I'm hoping this will fix everything. I'm tempted to add another ground cable on the other side of the engine, but am not sure if that's really necessary. I'll see how this works out first I guess.

Mike