Kubs

I did a search but nothing good came up. Where can I wire the switched 12v on the heated O2? I have a 1990, is there some sort of accessory wire close to the driver side header I could tap into?

Thanks

rodj

Any of the feeds that supply the pollution stuff are hot ;key on.
If you have deleted any of those you have a ready power supply or just tap into them

Kubs

I deleted the AIR and EGR systems. Are you saying one of the plugs from the black box the AIR tubes went into has a "hot" ignition wire? Which plug? Or are yuo talking about something else? I dont really recall any other emissions equipment with wires on them.

rodj

Correct;
the equipment has a 12V feed and is controlled by grounding back at the ECM so one of the wires is hot , key on.At work so don't have FSM handy.
If you have a DVM should be able to probe one of the old connectors and see which wire has 12V

MK 82

Get out your Student Mech Engr test light and do some probing. That's what most of us did.

Kubs

Thanks. At least now I know where to look. I dont have a FSM so this helps.

larryfs

add-a-fuse at autozone.

Kubs

I fuse in the hot wire to the O2? Shouldnt the wires going to emissions already be in a circuit with a fuse?

DarkBlue88

I used the main pink HEI distributor wire, with the white single terminal connector.

JAKE

Here's my experience: I first spliced mine into the windshield wiper motor wire, which was hot ONLY with the key "On". I later found that when the wipers were in intermittent mode, the voltage flucuated, dropping the system out of closed loop.

So I changed the power connection to the relay which is mounted on the driver's side wheel well. I believe it's for the fan on my 86.

Jake

West Point ROCKS!

ben73

I powered mine from the fuel pump relay. That way the heater is only powered up when the motor is running.

383vett

I'm not sure I would wire the hot wire for an 02 sensor to one of the emission solenoids, at least not without a relay and a fuse. The heated 02 sensor wire needs to be a heavy gauge wire and pulls at least 10 or 15 amps (a heater wire is essentially a short). The emission solenoids pull minimal amps (5 at the most) and would not be a good source for amps. I'd run a wire with a 15 amp fuse from the battery to a relay using one of the emission solenoid wires to close the circut. Safe and sound.

Kubs

Thanks guys. These are all things I will look into.

383 -

You say the heated wire needs to be bigger to carry the current. What gauge would be ok?

Midnight 85

You have a relay just below and in front of the master cylinder, I believe it's a fan relay?? I used the blue wire on it, it is a keyed power source and close to the O2's position.

Kubs

Thanks. Hopefully GM didnt move that between '85 and '90.

jmrl98

I'm with Jake - wiper motor. It's right there, and not noticeable.

Sinister87

I have done this also on my vette and t/a, don't drive either in the rain so I have never noticed if the cars go into to closed loop with the w/motor activated, I will have to try it out to see.

Kubs

Is this the relay? The one just behind the battery?



How did you tap into this blue wire? (Sorry Im not much of an electrical guy)

Midnight 85

The one I used is in front of the master cylinder, on the fenderwell. However, GM may have changed the location on the later years such as yours. Turn the key to the run position, then probe the wire with a test light, it it doesn't come on then keep looking or try a different color wire. If it does come on then shut the key off and try again so you know if it's keyed hot or not.

AGENT 86

I went with my OD relay because my O2 wires exited the harness beside it. Made for a neat and tidy install.
You don't have that relay, but the fuel pump relay is there also, which would make another neat and tidy install, provided your O2 wires exit the bundle there, too.
As for wire size, I would have to believe a 16 ga wire would be sufficient as it's probably the size of wire coming out of the heated O2. If not, just match the wire size that came with the heated O2.