Electrical dash wiring / wire color issues.

I'm rewiring a custom dash in my 1987 Blazer.

I'm used to just using my Amprobe with a pair of wire spikes and verifying these things as I need to.
Without power with so much of the dash opened and with thin gauge dash light kit in a custom aluminum entire dash console and dash board, I'm in the weeds.

* My battery is disconnected for safety because I have major wiring to do with fan relays, Compushift 2, 3 high voltage runs for the trailer brake controller Blue, a Red charging trailer wire and a 6 gauge hot run to my fuel tank yet to go.

The wiring diagrams are giving me a headache because they do not really specify the circuitry design or the correct wire color codes for the K5/K10, such as:

a) the single tank sending unit colors for sender vs power: (The wiring diagrams all show circuitry for the dual tank systems, as far as I can find).

I have purple, Gray and black. I'm reading 00.8 ohms between the Gray and Black ground.

32.6 between the purple and the black.
The fuel tank wiring question is required because I am attemting to over-size the main power wire.

I mistakenly stated months ago this upgrade was completed when I added the rear 175 A Buss bar, however when I dropped the tank to install new springs and the 14-B, the tank wiring portion of the project was not completed. Need to beef up that circuit.

b) the circuitry for the check engine light, ie: what color wire in the dash harness connector and does it get wired through the light to ground or does the ECM complete the circuit to ground to flash the light?

c) What color wire from the dash guages wiring connector is used for 4wd yellow light and how does it get a buzzer or a light?

d) Is there any provision for an alternator warning light or do I have to run a wire directly to the "I" terminal on my CS130 4 wire connector?
The connecter I have has only 2 wires in the connector and none where the diode circuit would need to be wired, according to a PowerMaster pdf I found.

e) My wires to the ignition column connecter are 16 gauge, not heavy duty 12 ga, like the pictures that instruct cutting the Purple wire for the ignition, on an automatic 1987, as the place to interrupt for Neutral safety.

This thread states in 87 the AUTOMATICS do not have a neutral switch.

This thread says the Purple wire is the correct place to cut for the Lokar neutral circuit:
Need to install Neutral Safety Switch on "87" to pass Canadian Inspection Auto to Super T-10 any suggestions on which wires would be appreciated :

http://forum.73-87chevytrucks.com/smforum/index.php?topic=39564.0

Can you confirm, please, this is correct and the Lokar switch can handle the full voltage this wire is sending?

I'm not certain if I need to add another relay in between or if this wire just sends a signal to the ECM to activate the starter relay circuit seperately.
Does it matter which side of the column connector I cut? I have a loop of wire that is purple under the connector, hanging down below the column that looks great, if it's correct.

f) where would you suggest I interupt the reverse light, so I can run it manually off a dash switch togle?
I see it's Lt Green and I know where the tail lights come through the firewall, however they turn into something else in the fuse box and get switched most likelt in the column.

Perhapse the same connector where the mysterious Purple ignition wire lives, might hide a back up wire color that will also allow me to cut at the column connector as well?

Again, I cannot test without making it hot and using my meter with spikes, so I'm in the dark.
The diagram is useless with regards to finding the way the circuits run off the page and do not connect to another page in the drawings, or maybe it's just me not finding where they run to another cut in the drawings.

When I cut the dash cluster connector off the dash harness, the Pink wire to the connector alternator circuit was factory wrapped, double back and cut 6 inches long, inside the black wrapper.

The other solid pink is supposed to be my fuel sending wire, so it's wired to my new auto meter fuel gauge.

Hopefully most of the diagram wire colors at the dash connector are correct.

I hope that my explaination is not too confusing.

_________________________________________________________
Here's the link to the post by "bd" where this .pdf file was found:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=39564.0

Using this diagram, found what I think is my 4wd circuit, IF my Blazer is the V300 version with just the 4wd indicator lamp and no shift lever circuit.

Could not define the V300?

Don't see where the Low 4wd buzzer used to live or how to wire it.
Hoping the brown with white stripe in the 4wd cut V300 is the brown /wt in the 15 pin on the cluster connector.

Have a yellow wire, which I think is the check engine in pin 13, but cannot be certain it is either hot or grounded by the ecm, as stated above.

I'm told the fuel tank sender will fry if I send the wrong wire 12v with a heavy duty power wire mod...
Suspect the yellow wire error might damage the ECM the same way?

No idea and not ready to burn up either unit.

I know where the fuel pump relay is and the wires do not match anything at the tank.

Anybody have experiance adding a heavy duty fuel pump 12v 10 gauge wire?
If so, what worked and how did you do it, and what should I be doing to occompish this task without 12v connected to test the circuit?

These six issues have cost me days or internet research, so I'm asking for your expert advice, please?
It's getting scortching hot im Montana and with thick cold weather blood, and a lot of stress from my 4L80E and transfer case re-manufacture, with a 14 bolt and spring swap, it's been tough.

We had snow 6 weeks ago and now it's 90.

UPDATE:

Found this photo, with a much better detail on the pin out for the 1227747 ECM in the 1987/1988 RV:

It shows the Orange with Black stripe as the 700R4 Neutral Safety ECM wire.
This picture above is completely different the the 1987 Typical wiring harness diagrams.

This diagram below, is not included in the Forum 1987 RV diagrams list either:


It shows the Orange/Blk stripe is closed to the system ground, Blk/Wht stripe.
This function is opposite of the Lokar neutral safety installation wiring instructions, which provides you with normally open when installing the detente ball.

However, the raised notches on the Lokar, can be adjusted to the Park/Neutral spots on the shifter and it will in fact close the circuit on Park and N, if adjusted correctly with the "banana slider bolts" (Lokar's terminology), on the passenger side of the shifter FIRST, and afterwards adjusting the cable and Heim joints to the correct locations for shifting AFTERWARDS.

Exactly backwards as the Lokar instructions.

It also defines the Brown / White Stripe, as the Check Engine or SES Light, depending on what diagram you are looking at. Very confusing, between diagram cuts.

It also shows the light bulb is in between Brn/Wht stripe and Pink/Blk stripe, WHICH IS HOT, after ignition. Positive, Not Negative...

The ECM controls GROUNDING the circuit to blink the light ON, NOT OFF.
When I pre-wired my gauges, I naturally wired all the black gauges to a common soldered ground and individually wired all the positive wires so they would get power from the harness loom wires, after the connector was cut off (and saved).

I'm not certain if it would have burned up the ECM or caused a breaker to short out.
It took a very long time to find these cuts on the web. It took re-reading this forum's documented diagrams listing and the forum remarks to find out several others had problems with the Blazer harness not matching the forum's list of options and diagrams.

Please consider adding/updating this 1998 RV diagram to the 1987-88 optional diagrams, because all the diagrams listed there are WRONG for the Blazer.
Apparently the Blazer in NOT Typical, as the diagrams are specified for Typical.

So at this point, without actually testing the circuitry, it looks as if the Check Engine Light b) neutral safety issue in question e) are possibly resolved.

If you have any reason I might have this incorrect, please chime in.

The fuel power circuit upgrade is still a mystery.

UPDATE 2:

The diagram for the 87' Blazer is the 88' Blazer for wiring fuel system too.
https://chevytalk.org/fusionbb/showtopic.php?tid/310389/

It looks like the pump gets a gray wire or a tan/wht wire, depending on the year and has various grounding scenarios. Sometimes the pump is made hot by the ECM and sometimes it gets grounded to activate the pump.

My pump has a short Black wire from the pump sending unit to the frame.
Now I'm testing to see if the pump runs with this ground wire removed or if it only effects the sending unit.

ChevyTech states in the thread above, GM changes mid-run and the books are all full of errors.

Great News.

Now to verify my pump hot tan/wht wire is actually hot all the time, or if it is activated by the ECM grounding it at the water neck, as stated may or may not be the case.

If the pump relay activates the pump motor circuit by an ECM ground, theoretically, I can run a fat power wire from the buss bar and move on.

If it does not and it activates the pump by providing a circuit (with wire colors changed) then I have to find out where the tan wire originates and find a way to beef it up without breaking the oil pressure sender circuit or screwing up the relay circuit.

Going to try and add the 12 ga wire by connecting to the FP relay test plug, which is hanging from the harness next to the FP relay. It's a red wire sticking out of the loom, with a single black plastic spade connector.

If I jumper power to this plug, with the key off, it might activate the tan/wht circuit through the oil pressure switch, which connects to the FP Relay circuit...

May be I can just add the fat wire to this red connector, run it to the tank and splice into the tan/white crimp connector there, and NOT cut the tan/white stripe wire whatsoever?

This gives me a 12 ga and the oem 16 ga wires side by side to the pump for better amp and electrical power to my HP fuel pump?

*** will update after testing.

Well, a lot has been accomplished.

Found the orange/black stripe is the neutral safety interrupt circuit to the ECM on the OBD1 1227747 for the '87.

The ball switch on the Lokar is now working to eliminate start in anything except Park or Neutral by blocking the power to the ECM, NOT the Purple wire to the ignition circuit, as explained in the thread above.

By deactivating the ability of the ECM to send power to the Fuel Pump relay, using the orange/black stripe wire, it is impossible to start in the wrong gear. Clean, simple and ready to roll.

The 12 AWG fuel pump wire is now soldered at the fuel pump relay, in-line with the Tan/White wire.

Ran it to the tank and soldered in-line, without cutting, to the gray wire at the fuel tank sending unit.

So the amps are full power to my expensive pump, without cutting the factory fuel pump harness.

The fans are all working, however the OEM K2500 fan has been removed from between the radiator, as a puller fan and a Spal 12 inch puller will be installed, directly to the Transmission cooler.
The OEM pusher fan will be mounted in front of the grill on a toggle switch, so I now have redundant fans for the transmission cooling system.

The water tight 40 amp relays that were $29 off amazon are working great, with 30 amp fuses and both running to a 40 amp circuit breaker at the battery buss bar on the driver's side fender, near the head lights.

The Carling toggle switches were $25 for 5 off eBait.
Pretty good deal for quality red led toggle switches.

Ran a 12 AWG wire through my firewall to power the Tekonsha Brake controller off a 30 amp circuit breaker.
Ran a set of 3 x 14 AWG blue wires for the electric brake circuit to the rear bumper connector.
The amp load loss from the Tekonsha to the trailer brakes, will be minimum, just like the fuel pump.

The dash wiring is now complete, less the wire to the alternator "I" terminal for the alternator warning light.
It will have to wait for now, however the dash light and the dash harness are all wired for the circuit.

My turn signals all work, the toggle for the back up lights, which could not be wired into the 4L80E or Lokar shifter, is working.

The check engine yellow dash light is correct and used the ECM to send ground to a hot light using the pink with black stripe to power the light.

The TPS harness for the Compushift is soldered in-line with the primary engine harness and the TPS connector. No crimps or spade connectors here, since the readings need to be spot-on.

The 4WD Brown/White stripe also is working with a yellow dash indicator light when the transfer case ball switch is activated for Low Gear 4wd.

Learned the black wire to the lamp completes the ground circut to the white wire to activate this light.

So the light bulb is in between the circuit of the same wire with different colored wires each side of the lamp.
It is NOT power on white and ground to black for the 4wd lamp.

Missing this would be a big mistake, just like the check engine warning yellow light, which gets ground from the ECM to light your yellow check engine circuit.

It is NOT intuitive. Triple check everything before you power up...

The 10 awg ground wire to the alternator battery 4 AWG primary ground, is now run to the bolt and steel bracket to the OBD1 1227747 ECM mount.

All the grounds for every 12v primary appliance now will ground inside the cabin to this home run ground wire directly to the alternator/battery primary ground star washer bolt.

The last bit of trailer harness connector wiring with the new Blue brake controller wire and the new Red or Black auxiliary charging wire to the connector is next. Then the Tekonsha Prodigy I scrapped from the K2500 can be plugged in and tested with a volt meter, while braking. Still not certain it even works.

In any event, if I need a new Prodigy 2 or P3, the harness and power circuit will be ready to go.

All the Compushift 2 TCM requires is the primary power circuit on a breaker and the transmission socket tested, then sealed with 3M 8000 to keep it maximum dry.

Used the 3m 8000 inside the terminal connector inside the 4L80E, so the CASE o-ring seal can NEVER leak into the connector pins and ground out my converter lock-up circuit. (Thanks Richard from TX on youtube!).

I had to pull a few pins on the original harness sent for the CS2 because it was wired for the Cadillac 4L80 FWD version of the 4L85 GM line. Because of this, the controller was much cheaper than brand new.

Pulled and relocated a few pins and it's ready for the standard 4L80E!

The holes it leaves in the weather seal of the connector could be plugged with small silicone plugs sold at Mouser for the Amphenol or Weather Pack connectors, of this class plug.

However sealing the entire harness inside and outside without using it on the actual o-ring between the connectors, is my plan to eliminate water OR transmission fluid from contaminating the OEM transmission connector.

Here's a look at the dash, as it's being diagnosed:

The hole is for another 2-5/8 inch gauge down the road.

My OTC compression gauge is hooked up for now to a -4an 60 inch brake line to the transmission test port. I bought the hose long thinking I would need to use it outside the vehicle and holding it out the window during testing on most vehicles.

When I drilled a hole for a grommet, I now have a lot of extra line to the gauge. It can be removed and used on other cars and trucks that do not have a grommet in the floor, so the slack is OK for my purposes.

When I replace that gauge for a dash mounted unit the same braided line will work with a shut off, in the event the gauge becomes damaged or leaks, under 300 psi the 4L80E is capable of.

Custom aluminum dash, made from sheets of an aluminum lined Coke cooler, the local grocery store was throwing out.
Large clean sheets of high quality aluminum turned out to make a sweet looking custom dash. Saved them for 6 years and they are now in my truck!

The rolls of wire in the picture, were scrapped from the local gas station, when they got a $6 MilUS retrofit.

Showed up the exact day the contractor was going to throw away all the old copper high grade gas station coated 14 AWG and 12 AWG home runs to the pumps from the registers. Wooo Hooo!

6 years in storage and they came in very handy to oversize all my heavy amperage home runs!

Water Tight amazon $29 Fan Relays, Head Light relays from Mod, 175A buss bar, where the second battery will live soon.:






I'll post more pics as it gets closer to complete!

Here's the transmission control harness external connector with the holes I mentioned requiring sealing compound or plugs, so the water does not short out the transmission:

Flex-A-Lite 16" S-Blade Fan and custom shroud:

PowerMaster adjustable 200 amp alternator for charging different batteries, AGM, Lead Acid, Lithium (if you can afford to rish using them).

RanchWelder said:

UPDATE 2:

The diagram for the 87' Blazer is the 88' Blazer for wiring fuel system too.
https://chevytalk.org/fusionbb/showtopic.php?tid/310389/

It looks like the pump gets a gray wire or a tan/wht wire, depending on the year and has various grounding scenarios. Sometimes the pump is made hot by the ECM and sometimes it gets grounded to activate the pump.

My pump has a short Black wire from the pump sending unit to the frame.
Now I'm testing to see if the pump runs with this ground wire removed or if it only effects the sending unit.

ChevyTech states in the thread above, GM changes mid-run and the books are all full of errors.

Great News.

Now to verify my pump hot tan/wht wire is actually hot all the time, or if it is activated by the ECM grounding it at the water neck, as stated may or may not be the case.

If the pump relay activates the pump motor circuit by an ECM ground, theoretically, I can run a fat power wire from the buss bar and move on.

If it does not and it activates the pump by providing a circuit (with wire colors changed) then I have to find out where the tan wire originates and find a way to beef it up without breaking the oil pressure sender circuit or screwing up the relay circuit.

Going to try and add the 12 ga wire by connecting to the FP relay test plug, which is hanging from the harness next to the FP relay. It's a red wire sticking out of the loom, with a single black plastic spade connector.

If I jumper power to this plug, with the key off, it might activate the tan/wht circuit through the oil pressure switch, which connects to the FP Relay circuit...

May be I can just add the fat wire to this red connector, run it to the tank and splice into the tan/white crimp connector there, and NOT cut the tan/white stripe wire whatsoever?

This gives me a 12 ga and the oem 16 ga wires side by side to the pump for better amp and electrical power to my HP fuel pump?

*** will update after testing.

Click to expand...

This information is incorrect.

Running a 12 AWG from the tan/white stripe wire to the gray fuel pump power at the tank, killed my ECM "B" fuse and would not run the fiel pump at start-up.

Please do not combine these wires in the 87' Blazer fuel pump relay circuit to increase the FP 12v signal. During my restart and after reinstalling the transmission, it failed to fire.

It will burn a fuse to the ecm.

Failed to increase voltage to my fuel pump.

If you have suggestions, I'm all ears.