The CRX

[DaveEstey]

Working on some aluminum door skins now. Mostly done.

[DaveEstey]

Alright it's time for a kill switch.

If there's anything I'm uncomfortable with in a car it's wiring... Any tips beyond taking it to somebody else?

[sdwarf36]

Make sure you get a 4 post kill switch and wire you altenator thru the smaller posts-other wise it is possible that even thought you kill the main power of the car, the alt can make enuff power to keep it running. (Don has checked this in the past. )
I actually like wiring-so my advice is first: don't go into the project loathing it-look forward to being proud of a neat + clean job.
Do as much out on paper as you can at 1st(and keep it with the car when done)-do 1 circuit at a time (and test them one at a time). Get a label maker or just mark things with tape.
Make a seperate small remote fuse block for all the stuff you are adding. Put it somewhere you can easily access.
Get a few different colors of wire + try to keep the colors matching through out the car. (white for fuel pump-green for water injection etc. )
Weld some 1/4" or 6mm bolts to the cage or body for grounds-head side down of course. More failures are because someone took a eylet + put a selftapper thru it-and it backs out slightly unoticed.
If you are gonna use hardware store crimp on connectors, get some GOOD crimping pliers. I have a set that has a "tooth" on the crimping surface that really puts a good crimp on things. Give a good pull test on every connection.
Put a glob of dilectric grease on everything. every parts store has it.
Use the least amount of wire as you can- If you have to run a 10 ft wire for + for the fuel pump-it doesn't mean you need a 10 ft ground-just ground the pump right where it sits. But dont leave the wires running banjo string tight-always leave some slack in case you need to reroute things-or have to make a repair.
When all is doneand tested, get a roll of wire loom and put all you wires in it-leaving everything clean + neat + out of site.

[walterclark]

I found I could reduce the wiring in my GTI some and reuse a lot of circuits (fuse location, wires already in harnesses, connectors) that had no use in my "race" car for things I needed to add. So I suggest you identify what can come out but dont remove it until you figure out most of what you will need to add. Some fuse boxes are not easily relocated to a place that is easily accessed but in my car it was on the end of a sort of wire harness that I could move from under the dash to up front on the console. That was a big help.

Document everything (removed and added) including colors of wires. I suggest you use the factory wiring diagrams and mark them up, then add pages for entirely new circuits. Label added or changed wires if possible. Label fuse functions or put a chart in the car. It doesnt take long to forget what things do if you dont have to fiddle with them much.

Be careful about what you bundle together. Anything that carries digital data or is fairly high current and switched on and off rapidly can interfere with other signals or be interferred with so consider shielding them or keeping them out of wire bundles.

Dont let wires or harnesses just lay on anything or crossover or thru metal seams and bulkheads unprotected. I put everything in split loom or spiral wrap and secure it with tie wraps. I put grommets thru bulkheads and a bit of door edging over seams that a harness can contact. Electrical tape is a good way to bundle wires together but is a terrible anti-chafe device. Friction tape is better but split looms are best.

[DaveEstey]

Well these are the diagrams I have. I need a multimeter now.

Seems like I don't actually have to change much. Run the positive from both the batt and alternator to the kill switch and then a ground. Am I way off base?



I need to remove the sunroof and A/C wiring.

[walterclark]

What you need to disconnect with the kill switch are battery power and the alternator field power.

The field, from what I can determine online for a CRX is a blue wire. Switching the blue wire off shuts down the alternator. You may find this wire or one that feeds it power coming from the ignition switch so you dont have to run a fresh pair of wires from the alternator itself. I saw some mention that the field comes off of a distribution block fed by the ignition, in which case switching the distribution block is good too. Dont switch the alternator high current output. In many cases switching this can kill the output diodes in the alternator and many kill switches secondary contacts cant handle this high current.

For the battery disconnect, there have been a different opinions over the years as to whether to switch the + or -. I prefer to switch the battery + and most of the online reference I find also prefer to switch the +.

Finally, some ECU do not behave nicely, if power is disconnected completely. If you find out this is the case with your car, you will find an unswitched ECU power input that is a sort of "keep alive" low current input. You can wire a separate fused path to this input if need be. The current draw on such an input should be a few milliamps so a 1A or 5A fuse should be plenty.

[DaveEstey]

Here's my ignition switch diagram




Not going to lie, this is all incredibly intimidating for me. I hate wiring.

[honda#72]

The blue wire,which switches to yellow/blue, would only kill the voltage regulator , it is the ecu's signal input, this wire lets the ecu evaluate the changes in charging signal.In my 90 crx manual your field power wire is white.

[walterclark]

I am glad honda#72 stepped in with good info. That is the problem with relying on web info and not having the service manual wiring diagrams.

Wiring and wiring diagrams can be intimidating, even for an engineer. For the last 10 years I have had just the VAG wiring and Dodge truck wiring diagrams to worry about. Both are pretty straight forward once I understood the symbols and structure and I would guess Honda is no different. My approach to wiring diagrams is to use them like a road map. Find the front matter that defines things like document structure, the symbols used and how it relates diagrams to physical location on the car and study it enough so you at least know what is located where in this section so you can look back there and find the meaning of something quickly. Once you decide to chase down, remove or install something, focus on the area you are in and where you need to go in the diagrams. Dont worry about remembering everything or following unrelated circuits. I found many diagram dont explain the value or purpose of what is carried by a wire so I end up going back from something like a light, motor, switch or sensor that I am interested in toward the ECU, battery, etc. to find where the other end of the wire is and what it might be doing. As cars get more complicated and you have computers talking to computers and almost nothing can be checked with a multimeter or test light, it just gets harder, but your generation car should still be pretty approachable with nearly everything outside of the ECU itself being 0V, 12V (or switching between 0 and 12V) or an analog voltage between and you can make sense of it with a multimeter or in the case of ignition and injection something like an oscilloscope (I use a freeware PC app to use the audio card to simulate a scope which works great for car use once you make up a couple test probes - I also have a high quality bench scope but dont use it much on the GTI anymore) or dwell meter.

[honda#72]

One more thing to note, DO NOT check the white/yellow or the yellow / blue wires from the altenator with a test light, or check resistence on them with a DMM, or let them short to power , with the ecu plugged in. The impedence will fry the solid state components in the ecu. These cars are super easy electronically, I wish that I still worked on them, on a regular basis, the newer ones are much more complicated , and sensitive to changes and input signal thresholds. An example of this is the crx etm is about a half inch thick, the 2010 etm's are now 3 inches thick and 2 volumes. As for the crx most chasis wiring will be 12v power to loads and 0 volts after the load on the ground side of the circuit. All loads should have a healthy 12 volt voltage drop. The only other times you will have a different voltage scale is in the PGM-FI system where some of your 3 wire sensors will have a 0-1 or a 0-5 volt , voltage scale , the 3rd wire is the ecu's reference voltage. Examples are your o2 senors which have a 1 volt voltage reference scale , and a stoichoi air fuel ratio (14.7:1) is .45 volts, or your map and tps circuits which are 5 volt scales. Your reference voltages will not always read accuratly with a DMM as the voltage change is some times too fast for a DMM to register, this is where a scope is very handy.One thing to watch when removing any wiring or painting surfaces , is that some sytems you may want to remove for weight savings, may share common splices to common grounds that may be running the important things you wanted to keep in the car.This can cause nightmares like voltage backfeeding thru the ground circiut. Some systems which you would never think would share circuitry do indeed.