Category Archives: Electrical


bowtie6‘s Custom Wiring – Under the Hood

After nearly 1,000 miles on bowtie6 since the ECOTEC conversion, I have a ton of stuff to detail out.  This is where you spend tons of time for little to show for.  Sure, I could just leave it “as is”, but there is no fun in that.  Sweating the details is what sets my car apart from all others.

Today, I spent some hours refining things in the main fuse box under the hood.  I’m not 100% done with it yet, but I figured I’d take a few pictures of it so far and write about it.  Maybe somebody might get some inspiration from all this work.

This is what the main engine-compartment fuse box looks like…

Big deal, huh?  Well the silver box is located in the area where the windshield washer bottle used to be and also the area where the dealer-installed air conditioning system was installed.  What is so special about this?  Well other than the fact this is all hand-made aluminium, take a look at what is inside the box…

Now it gets interesting…

  • Starting at the bottom of the picture are six circuit breakers.  Today, I added the little red “booties” to prevent any short circuits.  The middle breaker shows what they look like under the red “bootie”.  Two terminals stick out and this is what the “booties” protect.  Don’t want any electrical short circuits to happen here!
  • Above the circuit breakers are seven relays.  They control the most important basic functions underneath the hood.
  • Above that towards the right is a fuse panel with 8 modern spade type fuses.  These are used on the control side of the relays.  Basically they make the electromagnets in the relays trip when a switch makes ground.
  • The finned box with the three big connectors is the Engine Control Module (ECM) running the show on the ECOTEC.  This is “factory” supplied from the donor engine.
  • To the left of the ECM is the solid state electric fan controller.

Circuit Breakers

These guys act as fuses.  They feed the hard voltage from the B+ terminal through the firewall to the relays.  What B+ terminal?  Since the battery is located in the trunk, we ran a welding-machine cable from the battery’s B+ terminal through the firewall by means of an insulated bolt.  This is where we get voltage to the underhood fuse box and also to the inside of the cab (on the inside side of the bolt)

This is a close up of what this all looks like:

At the very left you see the post where full B+ voltage is supplied to the circuit breakers.  The body and frame is ground so how does this keep from shorting out?  The bolt is fully enclosed in a phenolic ring thus insulating the terminal.  On one side of the circuit breakers is the hot B+ terminal – this is the one nearest to the camera.  On the other terminal is the supply of power to the relays shown above.  On the middle of each circuit breaker you can see the little black dot that acts as a “reset” button.  I used circuit breakers because these are 100% essential to the electrical operation of the system.  If they trip a simple push of the black “reset” button has me back in business.


Seven relays run the show for the main switched hot lead, ECM, headlights switch, high/low beam, electric fan, horn, starter and ignition switch.  All the switches on bowtie6 break ground.  There is no hard voltage going through any switches.  The advantage of this is longevity.

So basically when a switch is activated, it “makes” ground.  This in turn causes the electromagnet in the relay to trip and that makes the circuit hot.  There is no hard voltage through any switch except for one:  ignition.  I am using an industrial strength switch for this, rated for much higher amperage than what the Optima battery delivers.  This will last past my lifetime.


There are 8 fuses under the hood.  These supply power to the control side of the relays as well as to the ECM and the electric fan controller.  I used modern style fuse housings and bladed fuses.  Glass fuses are just too poorly made and prone to failure and that makes them very unreliable.  Not acceptable for bowtie6.

ECM and Engine Harness

The “brains” controlling the ECOTEC is the GM factory E67 ECM.  The wiring from the ECM to the multitude of sensors on the ECOTEC is basically a factory harness from a Chevy HHR, modified to act as a Pontiac Solstice.  We modified the harness by changing pin-outs and removing unnecessary circuits.  This makes the harness much simpler to work with.  Furthermore we cut many wires to make them shorter or longer depending on where they were located.  This is the beauty of doing it “yourself” as opposed to buying something.  Anybody can “buy” stuff…  It takes talent to make you own.

Like I said before, the harness came from an HHR.  GM went through a lot of work in making a very durable and well engineered harness.  In my opinion, the quality of the wire is superb and the connectors are not only expensive but of very high quality.  The harness is basically divided into three “plugs” (you can see them in the picture above).  One has 56 pins; the other two have 73 pins.  Not all are needed though and having a Factory Service Manual will be instrumental in determining what circuits are kept and which need to go.

To make the ECM work outside of the “factory” setup, one must remove the VATS.  This is the “Vehicle Anti-Theft System”.  You do this either sending the ECM out to somebody or by using a software package such as HP Tuners.  We used HP Tuners.  This also enabled us to tune the ECM.

Speaking of the ECM:  make sure you get the right one.  The ECM’s come in two varieties depending upon the type of gearbox used.  An automatic gearbox ECM will not work on a 5 speed gearbox.  Also, there are certain E67’s that will just won’t work.  You will need to make sure you get the one with the right OS, otherwise it won’t work.  This is why it is very important to get the ECM that came from the donor vehicle.

Solid State Fan Controller

This little device is trick.  It has a built in relay and has B+, ground and a wire hooked up to the temp sensor on the block.  This is where the device gets its temp signal.  Here is the beauty of this device:  on 99.99% of all street rods I see, folks stick a nasty looking probe in the middle of the radiator core.  This not only looks awful but eventually wears a spot in the radiator’s core causing it to leak.  I think this way to wire a controller not only looks crappy as hell but is very sloppy.  The controller we use is not cheap, but it has a fully adjustable rotary knob that enables setting the proper temp to kick the fan on.   In the photo above the controller sits on top of the ECM but I am planning to move it to a different location to make it look a little more elegant.  Again, it is the details that count!

In Summary

I realize this is not everybody’s cup of tea (a polite way of saying “I don’t like it”) but once again this works for me and the car has been built to suit me not anyone else.  I wired the thing, I know each circuit and quite frankly I am proud to say it is bullet proof.  I blew a fuse one time, but that was my dumbass-self making a mistake.  Again, one can source a ready made wiring harness but what do you learn by doing that?  I spent a lot of time learning about circuits and how relays, fuses and circuit breakers work.  This takes time but the result is very rewarding.

If you do decide to undertake something like this, there are a few things I would highly recommend:

  • Every single terminal (and there are many) is soldered – nothing just crimped.  This is extremely time consuming but worth every moment you spend on it.  Soldering ensures a perfect connection and if you are going to spend this much time, you want it to be dead-nuts-accurate.
  • I used the expensive shrink wrap that has the sticky stuff inside of it on every joint, every terminal and every splice.  Why?  This makes the connection water and moisture proof.
  • Anytime I had to join parts of the harness, I used Weather Pack connectors.  They are not cheap, take a long time to crimp and assemble but they are water and moisture proof and last forever.  This is the only way to go.  By doing the harness this way you can ensure certain parts can be take apart without removing the whole shebang.  There is a bit of strategy to play here but you will be very happy with the result.
  • I spent quite a bit of resources on only the best quality wire.  All my wire came from an industrial supplier, not from a home-improvement store.  This is industrial strength. The real-deal.  I did this the first time with the V6 and it lasted flawlessly for 5 years.  This time around I expect it to last much longer since we are braking ground instead of switching hard voltage.
  • Relays – buy only the best (mine are Bosch) and don’t be stingy.  Relays are the way to go.  Once you get the basic principle of how they work they are fantastic.  This folks, is not rocket science and is not black magic.  Relays work and if you do it right, they last forever.
  • Use the proper tools.  I say again:  use the proper tools  I used good quality nippers, soldering gun, heat gun and crimping pliers.  The Weather Pack connectors require a special crimper.  Use the best you can afford.  Otherwise you will have crappy connectors and this will lead to electrical problems and the dreaded “Lucas Syndrome” where wiring turns into very expensive blue smoke.

I could write about this forever but then again, I would bore the hell out of you.  If you have any specific questions let me know and I can address them in a separate post.

Go do some wiring!  It is not as complicated as the harness “makers” make you believe it is…  🙂


Wiring Harness Milestone

After doing the tourist “thing” last weekend with wifey and not getting work done on bowtie6, this weekend was balls to the wall.  Fortunately, the planets were all in alignment and things worked out satisfactorily on the wiring front.

Since the wiring harness on bowtie6 is 100% custom (nothing “bought” here folks), this has taken quite a bit of time to design and build.  The premise has been to divide the car in three sections:

  • Engine Compartment:  circuit breakers, fuses and relays controlling the ECM, engine sensors, electric fan controller, headlights, main switch.
  • Cab Compartment:  fuses and relays controlling all instrumentation, heater fan motor, turn signals and switch, windshield wipers, headlight switch, parking lights switch, horn.
  • Trunk Compartment:  fuses and relays controlling all tail lights, fuel pump relay, fuel tank sending unit.

Yes, this is an unorthodox way to wire a car but is bulletproof.  All hard voltage switching is done with relays saving wear and tear on delicate switches.  All switches basically break ground and this makes for a very easy to diagnose system.

Well, today everything in the Cab Compartment and Engine Compartment was powered up and it all worked “the first time”.  No smoke, no blown fuses.  That’s the way we do things.

The ECOTEC has been fully functional for several weeks now.  We have let it idle for enough time to bring coolant up to operating temp and beyond.   This has enabled the electronic fan controller to kick in and run the SPAL fan enough to bring temps down and turn the controller and fan off.  The fan runs for about 30 seconds and shuts off.  It is cycling properly and this is the mark of a truly well designed system.

With today’s work, the parking lights were turned on; ditto for the headlights.  The floor controlled switch caused high beams to fire up as required and turn signals worked also flawlessly.  Inside, the wipers worked both in low and high speeds and the new heater motor’s three speeds worked as expected.

This leaves the trunk compartment to be done.  There will be a small fuse box along with a few relays to control all the rear lights and fuel pump.  Plans call for a small enclosure for all this and hopefully with a little luck, all wiring will be completed soon.

Fall is just around the corner and I just can’t wait to get bowtie6 back on the road…

Wiring Up the Gauges…

Moving along on the wiring, albeit slow.  Today, I spent 6 hours working on wiring up the instruments.  I was able to re-use some of the looms I made up the firs time, but had to make plenty of alterations along the way.  This is what it looks like from the backside:

The gauges are VDO Vision.  The have been great and are all electronic, compatible with the ECOTEC.  The speedo is programmable, so it is 100% dead nuts accurate.  The backing plate is aluminium and the front is made from quilted maple (I’ll have pics of the front in a later installment, once the dash is in place).

I realize this looks perhaps, unimpressive – but a huge amount of work has gone into making this up.  Every single connector has been soldered and shrink wrapped.  Since I wanted to make this so it can be removed easily, every circuit is connected to a “Weatherpack” connector.  This is why it has taken so long to make.

The following picture shows the dash area in bowtie6 before the dash goes in.

So…  What do we have here?

  • The heater has been replaced with an aftermarket unit.  The “original” heater unit I used to have developed a leak.  A little research found the unit pictured above which was a) cheaper and b) more efficient.  Plus it is able to withstand higher pressure.  This is desirable since it allows a high PSI cap on the radiator.
  • The transmission tunnel has been made from scratch to match the ECOTEC’s AISIN 5 speed gearbox.  It will be covered soon in Dynamat Extreme, just like the rest of bowtie6 has.
  • Finally, the piece de resistance:  If you look close, you can see the steering column is now fully adjustable.  Yes, a special mechanism has been made by my cousin Jim that allows the column to tilt with the flick of an adjustment bar.  I’ll have more on this later, once I get it all bolted back together.  Trick, huh?

This wiring effort has been very time consuming, but the end result will be fantastic.  There is a huge satisfaction from wiring up a car from scratch.  Not many people can do this type of work – it takes patience, but it sure is a lot of fun.


bowtie6 Wiring – Part II –

Engine wiring is progressing right along,  albeit slow.  This part of building a car takes time!

So far the engine harness is complete.  All wires to the ECM have been accounted for and the main looms have been covered with crinkle tubing.  This tubing protects all wires and keeps things looking neat and professional.

Another engine bay picture showing the fuse box on the left, the coolant overflow tank, coolant lines and brake master cylinder and hydraulic clutch reservoir.  The coolant expansion tank is all hand made aluminium.  Missing from the coolant expansion tank is a small rubber hose going to an overflow tank behind the radiator; also hand made aluminium.  And yes, all the rubber coolant hoses are missing their clamps.  Just haven’t had a chance to get there yet!

Below, is a close up of the new fusebox.  On the bottom left, you see the new fuse box.  This is where all the relays, circuit breakers and fuses that control the engine compartment reside.  This is what it looks like:

So what do we have here?

Starting from the bottom:  below the box, hidden from view is a post that goes through the firewall.  This post is insulated with a Bakelite insulator.  From this post, wires feed battery power to the circuit breakers.  There are a total of seven circuit breakers; one for each relay.

Above the circuit breakers there are seven relays.  They are used as follows:

  1. Horn relay
  2. Electric Fan relay
  3. Headlight “on” relay
  4. Headlight high/low relay
  5. Starter relay
  6. Ignition relay
  7. Start button relay

Finally above all this are two banks of fuses.  To the left of the fuses is the electric fan controller and below that, the engine’s ECM.

Why so many relays?  The idea here is to use a relay for each device that requires high current, for example the electric engine fan.  The idea is to let the switches run low current controlling the electromagnet in each relay.

I know what you are going to say:  where are the turn signals and parking lights?  Yes, they have been left out.  Not by mistake, but by design.  Underneath the dash will be a smaller fuse box, containing fuses and four relays.  This is the part I’m working on now, and will be featured in the next installment…  Stay tuned.

bowtie6 Wiring – Part I –

Making a custom wiring harness is an interesting process.  It takes time and careful thought.  Is it for everyone?  No.  This is the second time I’ve wired bowtie6 and this time, I’ve applied several lessons learned from the first time.  Basically:  make things as easy as possible.

I’ve written previously about all this but I thought it would be nice to give a more in-depth view of the work I’ve done.  Maybe this might be of help for someone, so let me start with the engine.

To start with, a factory GM engine harness was sourced.  Contrary to popular belief, one does not need to buy a special harness (they are usually very expensive) to make an EFI engine run.  When properly modified a factory harness is an excellent starting point:  all the sensor plugs are there and the wire is of excellent quality.  Special care has to be taken however, when the harness is extracted from the donor car:  you want to make sure you get all the plugs and pigtails, including the fly-by-wire throttle pedal and its wiring pigtail.

I’ve seen many conversions where folks take an original harness and along with that, the instrument cluster, fuse box, firewall connectors, steering, etc.  This results in a cobbled up, complicated affair.  Why?

  • The donor car’s instrument cluster is kept because modern EFI will not get along with original, mechanical instruments.
  • The steering column is re-used because of the special vehicle anti-theft device that depends on the special tumbler and key to make the engine run.  This is commonly known as VATS – Vehicle Anti Theft System.
  • The original engine fuse box is retained because it is already made and it just “works”.

There is a better way.  In my case, the harness was sourced from an Ecotec powered vehicle: a Chevy HHR.  With the aid of the factory service manual for the Solstice/Sky, the harness was simplified by removing unnecessary circuits.  Many wires were shortened and by doing this the harness was greatly simplified and made to fit the engine bay of the TR6.  I did this because again, I’ve seen many conversions where people don’t resize the harness and this gives the engine compartment a very cluttered, busy look.  I’ve also seen conversions where great care has been taken to hide as much of the harness as possible.  This gives the installation a very professional, “factory” look which is not easy to do but if you take your time makes a huge difference.

In the case of the older six and eight cylinder engines the VATS can be disabled by adding a small, inexpensive aftermarket module or by having the ECM modified.  This solves the problem of having to use the original key, tumbler and steering column.  With the previous V6 in bowtie6, I used the aftermarket module.  It basically had a switched hot lead, a ground wire and a wire that was in turn spliced into a pin on the ECM.  With the Ecotec, we did not use a module instead we used software running on a laptop to disable the VATS circuit.

The ECM came from the same donor HHR the harness came from.  This gives a good starting point and is compatible with all the sensors, fly-by-wire throttle, etc of the “original” vehicle.  In my case, I’m running the 5 speed gearbox as fitted to the Solstice/Sky therefore the separate computer used to run the electronic automatic gearbox is removed – this was part of that “simplification” of the harness I mentioned previously.

After all the work of checking every wire for continuity, removing unnecessary wires and length alterations, several loose wires were left:

  • There is one unswitched hot lead that keeps the ECM alive.
  • There are a number of switched hot leads.  These control items such as the O2 sensor, injectors, coils, etc.
  • There are a number of ground wires that must be tied back to either the engine and consequently the engine must be grounded too..
  • The ECM controls the fuel pump.  Therefore there is a wire from the ECM that eventually goes to a relay that energizes the pump.

This pretty much wraps up the engine harness.  All this has been done so basically bowtie6‘s Ecotec is all wired up.  Not for the faint of heart, this process alone has taken many hours to accomplish.  There is not easy way out here, but the result is very cool indeed.

So what is left to do?  I’ve taken a different approach this time.  The first time I wired bowtie6, there was one central fusebox where all circuits originated from.  This was fine and dandy.  The fuse box was hidden behind the dash but the problem was twofold: 1) a huge amount of wires coming and going and 2) it was extremely hard to get to.  I once had a fuse blow and it was a hell of a job to find the blown fuse.

This time, the new harness is simpler and has been broken down into three main sections:

  1. Engine compartment:  this section will hold the main circuits managing the engine harness.  I’ve also included the headlights, horn and electric engine fan circuits.
  2. Occupant’s compartment:  basically inside the car.  A separate smaller fuse box will control all switches, instruments and heater.
  3. Trunk compartment:  the last small fuse box where the tail lights, reverse lights, fuel pump and fuel sending unit are all controlled.

In the next installment I’ll have more details about the engine compartment wiring which has been completed.  Stay tuned…