I left my complete LS harness intact and crimped a new end on the main power wire to the chevy + block. That took care of starter and alt power
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
thatcabledude
GOLD Star
Yeah i didn't do anything . Factory GM 4wire harness, and factory output wire to the little red "battery +" box that mounts to the side of the alternator bracket.
bloc
SILVER Star
If you use a GenIV engine with the 2-wire alternator you either must convert it to 4-wire (which requires soldering a new VR onto it), dealing with low charge voltage, or integrate the GM body control module to control the 2-wire alternator.
If we are talking GenIII engines, I don't have any experience with it.
If we are talking GenIII engines, I don't have any experience with it.
I already converted my to 4 wire but I do not know if Toyota already has resistor in line
Can anyone tell me what the 2 smaller terminals are used for on the brake light switch? They function just the opposite of the actual brake light switch, and would be ideal for the TCC / ECU connection, but I don’t want to tap into it till I know what it’s prime function is. Tried to find it in the EWD but gave up after guessing what it might be for. Thanks for any insite.
That was my experience with the Gen IV - I had to solder on a new VR.
I just ordered a Gen IV harness from Howell for another swap and the guy swore they could control the alternator through the computer. He did ask if it was a 2 or 4 wire alternator.
I questioned his statement, but he stood firm. We’ll see.
Anyone know what pigtail to use for the speed sensor on the marks adapter?
bloc
SILVER Star
The other circuit in the stock brake light switch is for the cruise control interrupt. Look at the CC EWDs and it'll make a lot more sense.
As stock, at least in trucks, the BCM controls a 2-wire alternator.. through the ECM. The primary input is an ammeter that goes around the negative battery cable.. the BCM can measure system voltage directly, but not amp draw, and with this input can up or downregulate the alternator much more quickly. It can respond to amp draw immediately, vs having to wait for the voltage to drop. Thing is, it is all indirect. The actual 2-wire control comes from the ECM, and presumably the BCM tells it what to tell the alternator via GMLAN. I'm reasonably sure it's high-speed GMLAN as I don't have any of the low-speed stuff wired up, for the record.
I don't see a reason the ECM couldn't tell the alternator to look for a certain target voltage, but it won't work quite like stock. Also, while I see the alternator controls in HPTuners, I did mess with them and couldn't get any more than the 13.8V that is so common. Lots of discussion of this on the HPTuners forums, IIRC. I didn't dig too deep, as my plan was to use the BCM all along. The moment I got it and the ammeter wired in, voltage went exactly where it should, headlights and dash lights brighter, etc.
bigger terminal is for brake and smaller is for cruise control that is what i used to since toyota cruise will not work anyway
thatcabledude
GOLD Star
I got it figured out. It was actually the power feed to the sensor . I kinda blindly followed rockrod’s pinout sheet, and it called for deleting pin 5 from connector IH1 under the dash which turns out powers the speed sensor. Luckily I was only missing the wire from there to the one that sits on top of the trans. The rest was still intact.
My rear diff lock started doing the not working blink today. I'm worried that a part time spool in the t-case may have been a bad idea combined with 150 extra hp. I'm afraid of seeing what the rear diff looks like.
I went with a 4 wire ,Gen III style alt. I went into HP tuners and unchecked the box for smart charging. It now charges great, something like 14.5 volts. I forget how the box is exactly labelled in hp tuners but it was easy to find in the charging system area
but did you use all wires from toyota alternator without resistor
I used no wires from the toyota. The wiring and plug are part of the new engine wiring harness
bloc
SILVER Star
I found it, and could turn the alternator on 100% duty cycle, and seem to remember being able to give it a specific duty cycle.. but I couldn't get the alternator to charge as it should using 2-wires and the factory gm ECM with HPtuners.. and this seems to be common.
Can anyone recommend a radiator solution for my 92 80 series with a 5.7 tbi? I am running the one flex fan and the stock radiator but the temps are fluctuating 190-215 degrees. I want you t to be more like 195 -200.
thatcabledude
GOLD Star
You have the only TBI motor swap I have seen. Definitely the only one in this thread. Mine stays right at 190° with a factory GM mech fan, homemade shroud, and stock cruiser radiator. GenIII motor here though.
When you say "flex fan" is that an electric or mechanical?
Mechanical fan.
