ssvolvo

Hi guys, Just finishing an LS2 Volvo 940 swap and one of the last items is getting the charge light in the Volvo dash to work. Since the LS2 alternator hookup is quite different from the LS1 setup I'm unsure of tying into the alternator harness for charge light operation. The plug on the LS2 alternator has 4 terminals but only the center 2 are utilized. The other 2 cannot be used since the plug is only formed for 2 connection. The ECM has a turn on signal and a duty cycle for proper voltage. The light in the dash (on a GM car) is turned on through serial data line that operates other guages also.
If I can't figure this out I might try building a simple board that will unground the Volvo dash (battery) light over a certain voltage. I was hoping for a simple solution. Wiring diagram enclosed.
Thanks for your input

rao

iTrader: (18)

Interesting problem.

What signal does the light on the dash see in the Volvo?

ssvolvo

Just a simple light bulb circuit. The alternator provides the ground.

Schitzo

iTrader: (6)

Does it provide the ground with the alternator running or when not?
I know nothing about volvos but id imagine if its your generic BATT light circuit then one side of the bulb receives IGN 12v and the other would receive 12V from the alt when running. If the alt is not running then the alt end is grounded hence the BATT light comes on.

One way to go about it is to ditch the PCM trigger and hook the charge light instead but I guess that would throw the MIL

Im also interested if there is a way to hook up a charge light and still retain the PCM trigger

ssvolvo

Yes a generic light bulb circuit just like any old Chevy up to 04. I'm using EFIlive so I can ditch the code. I might be a bit **** so I'd rather not. Would love to have the light work correctly and don't mind spending some money to do so...whatever it takes. This is a really nice swap. Homegrown stainless long tubes an full stainless exhaust, aluminum everything else. I'm a geezer...I'll drive this thing till I die; really. Have mucho time and money invested in it, and wan't it right.
I'm thinking of making some kind of voltage operated switch that will trip a relay at say 12.8 volts so I know it's charging. I thought there might be an easier way. I Checked Street & Performance tech stuff but no luck. This should be a no brainer for any LS2 swap. Looks like I'm the first guy with an E-40 ecm who wants his battery light to work in a non-gm car....go figure.

Geezer's Garage

And I'm the second guy who's trying to figure out the same issue. I just fired my Gen IV 5.3 in my 1987 535iS BMW for the first time yesterday--well, first time in the car. I'm going to run an accessory volt meter but I was thinking it would be nice to keep the BMW warning light also. I was tracing wiring diagrams over the weekend and hadn't figured anything out. Let's hope some smart guy brings us an answer.
The Geezer

ssvolvo

GEEEEZ Geezer. Where ya been hiding? followed your whole series on youtube but it's like you vanished.
Anywho I think I found an answer. I found this relay on the net. Haven't bought it yet. It's adjustable check it out. It can be wired to ground the bulb in your BMW dash at a certain voltage. You can leave the alternator right out of the equation with this gadget. http://www.kussmaul.com/091-96-12.html


Geezer, I have the same engine in this old Volvo. Hoping for 30 MPG. Hope I'm not blowing smoke!

ssvolvo

Anywho,
For those of you wondering about the LS2 battery light in a conversion. That relay link I posted in last post turned out to do the trick. Now my battery light works just fine. Easy to wire up (under the dash) and great directions. The bad thing is the cost (about $60 bucks).


Oh and on European cars of the early 90s with an airbag. That battery light also tells the airbag ECU that the engine is running. This is important!

Schitzo

iTrader: (6)

Thanks for the update. How did you hook it up? splice into the trigger wire or just connected it to a different 12V source?

ssvolvo

The primary side of the relay just needs to sense voltage to be able to switch on or off at an adjustable voltage setting. I just hooked that part through the ignition switch. You can download the directions and see how the relay works. You can use it either normally open or normally closed to suite your liking. It comes preset at 11.8 volts. I bumped it up to 12.6 since that is the voltage of a fully charged battery.
Works great, John