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Electrical Question for this 3 bay fuse block in engine compartment

In the lower left hand corner of the picture below, I have two of the 3 slots filled as I'm sure most of you have as well.

I am attempting to install an AFR gage and I need to find a 12v source that is activated by the ignition.

In the two fuse slots below, they are both hot all the time with 12v. Is this normal? Should one of them be activated by ignition?

Can someone help me find or locate an ignition activated power source along with helping me determine what is wrong if anything with my constant power on the two 25 amp fuses. Please ignore the plug in the white circle, this photo was from a while ago and the only good one I have of that area.

Thanks,
Bryan


Old 11-19-2008, 10:15 AM
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Sorry

Just in case it matter, 1987 930. Thx
Old 11-19-2008, 10:16 AM
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Quote:
Originally Posted by x98boardwell View Post
Can someone help me find or locate an ignition activated power source. . .
Thanks,
Bryan
The WUR and AAR 12V supply is Ign. switched. Should be easy to tap into that supply. Don't know what current requirement for the O2 sensor is but be sure the tapped circuit can handle the added load.
Old 11-19-2008, 11:14 AM
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Thanks

Chris,

Thanks for the input. I know where these plugs are but not sure where they start so that I can tap in.

Also, I would think there is a 12v switched power source somewhere near that panel so it's easy to tap into.

Lastly, does anyone know if the 2 fuse blocks should be hot all the time which mine are?

Thanks,
Bryan
Old 11-19-2008, 12:44 PM
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Mine are hot all the time as well.

I used the hot lead going to the CDI


Perhaps you can still use it if you are using the stock ignition?



Quote:
Chris,



Thanks for the input. I know where these plugs are but not sure where they start so that I can tap in.



Also, I would think there is a 12v switched power source somewhere near that panel so it's easy to tap into.



Lastly, does anyone know if the 2 fuse blocks should be hot all the time which mine are?



Thanks,

Bryan

Last edited by A930Rocket; 11-19-2008 at 02:31 PM..
Old 11-19-2008, 01:21 PM
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Quote:
Originally Posted by x98boardwell View Post
Chris,

Thanks for the input. I know where these plugs are but not sure where they start so that I can tap in.

Also, I would think there is a 12v switched power source somewhere near that panel so it's easy to tap into.

Lastly, does anyone know if the 2 fuse blocks should be hot all the time which mine are?

Thanks,
Bryan

In the SC, 2 of the posts are bridged on the backside by a permanent metal connection as as well the front removable bridge . I removed my 3-block and cut the bridge with the dremel wheel to gain additional switched connections for my EFI. I can't tell if the fuse block is different between the SC and 930 from my copy of PET you may want to unbolt it and look at the backside.
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Old 11-19-2008, 01:26 PM
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Quote:
Originally Posted by x98boardwell View Post
Lastly, does anyone know if the 2 fuse blocks should be hot all the time which mine are?
Mine are hot all the time, at least one of the two anyway. Discovered that one day while trying to trace down a constant power drain on the battery (another very long post that I left somewhere).
Old 11-19-2008, 01:44 PM
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Thanks

Guys,

Thanks for the heads up. I also have the bridge there.

Do you know of a ignition activated 12v source in that area that I can tap into? This is what I am looking for and its not clear where I can find it?

Bryan
Old 11-19-2008, 01:59 PM
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I should have taken better notes when I did my new CDI, but I think I found a wire in the harness leading to the 14 pin connector and tapped a line there.
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Old 11-19-2008, 02:24 PM
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This is the fuse block from the '83 SC:



on the left hand side, the upper large red wire is always "hot" and the lower red wire is switched "hot" to the heater blower relay. This is the "switched" input that I used. Since I back dated the heater system, I removed the central red/white connection to the heater/blower relay on the right, inverted the bridge and cut the rear bridge to gain an extra "switched" fused lead. The lower yellow fuse is now the switched circuit for my wide-band controller.






I don't know how similar this is to the 930 so I hope it helps.
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Last edited by sjf911; 11-19-2008 at 10:32 PM..
Old 11-19-2008, 10:29 PM
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Ok

Steve,

Thanks for the response. The 3rd slot (the one on the bottom) on my car is open and not being used at this time. Also, both of the top two slots are hot all the time so I'm not sure where my switched power source is.

I could try to tap into a few of the lines with a pin to see if they are not currently hot and then remove one and add that 3rd fuse as you described above.

If you look at my original photo it seems that I have more wires feeding into the slots. I wonder if that is correct or if someone has introduced some new wires over the years? Not sure,

Any other ideas? Thanks for the help Steve. That will be an option if I cannot come up with another solution. I would have to remove the IC and a few other itmes to have good access to that area, but since I have removed it about 10 times in the last 2 months, it will only take a couple of minutes.

Bryan
Old 11-20-2008, 07:44 AM
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Sorry about that. I don't have access to a 930 wiring diagram. You should be able to identify a switched hot source in the engine compartment with the appropriate diagram to tap and pull out in your fuse block. One or more of the existing relays should have a switched source as one lead.
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Old 11-20-2008, 08:42 AM
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Do you absolutely have to tap into the engine bay for switched power for AFR gauge? For example, if its the LM-1, you can tap into fuse 4-6 (on the 10 position fuse block in the front) for switched power (these 3 will have power when ignition is ON but not cranking).

At the engine bay, perhaps you can try pin 2 of the multi-pin connector - it should be connected to the delay reaction relay and has power when switched-on (but also turn off last).
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Old 11-20-2008, 10:43 AM
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It may not be a good idea to tap into the WUR or AAV electrical heater circut because that is the same circut both fuel pumps are running on and it's already taxed. It might only be around 10-11 volts too.

It may also have more RF electrical noise than any other circut in the car because 2 electric motors (930 fuel pumps) and the heating elements in the warm up devices are running on that fuse and relay circut.

When I installed an Innovate LC-1 the instructions said you shouldn't hook it up to a power or ground circut with alot of electrical noise in it from other devices because it could mess up the LC-1's processing.

I ran some wires up front along with the AFR gauge wires and hooked mine up to the fuse in the front compartment of the car that has the electric mirrors and one other rarely used thing hooked up to it. I think it was 2 fuses forward of the fuel pump fuse. That was the 8th fuse forward from the windscreen bulkhead I think...
Easy to figure out anyway.

I ran all the LC-1 and gauge ground connections to the engine block in the back corner where the air pump used to be.
Old 11-20-2008, 11:31 AM
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JFair has good advice. Let me add to it:

I also remember reading in the intructions that the innovate products should not be hooked directly to switched power. The reason being, is if you leave the ignition on w/ engine off for any length of time, the O2 sensor heater will be powered up. I forget all the possible faults w/ this. Something about leaving the key on for a while, getting the sensor hot, then cranking the car and exposing the o2 sensor to exhaust condensation from cold start can ruin the sensor heater instantly. (think hot glass & cold water=destruction)

If I recal, on the later cars, the AAV and WUR do not power up until the fuel pumps are running, as J said. If your blue connector is still plugged in on the Air flow sensor plate housing then your pumps shouldn't be running w/ key on until you crank the engine.

It's probably best to use a standard 4 or 5 pin relay. Connect terminal 30 to the fuse box mentioned above, connect 87 (NOT 87A!) to the power supply to LC1, connect ground to 85. And tie into the wire for the AAV/WUR at the 14 pin plug for 86 (note: you can reverse 85/86) polarity doesn't matter)

You can get the relay w/ socket at most any generic auto parts store.

I'm sure someone can chime in on which wire to tap into. You can do it right at the 14 pin plug, and considering it's only tripping the relay, it will not have any significant current drain to the system as well as the LC1 will be isolated from noise, etc. by the relay...

Hope it helps
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Last edited by rsrmike; 11-20-2008 at 11:55 AM..
Old 11-20-2008, 11:52 AM
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Solution

Unfortunately, since the LC-1 unit sits in the engine bay I need to keep it there. I have decided to do what JFairman said anr run the power up to the front and use the same 12v source that I used for the actual gage up front. This will ensure that it is a true 12v switched source.

It such a pain in the a$$ (when doing it right) to run the wires through the engine bay up behind the tranny and through the tunnel where the reverse lights enter, but to do it right, I guess this will be my best option. I will install an in line fuse before I connect to be safe.

Thanks to everyone who responded.

Bryan
Old 11-20-2008, 11:54 AM
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check above your last post, we were typing at the same time apparently...
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Old 11-20-2008, 11:57 AM
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Why not use the hot lead to the CDI? You could run a wire from there to the 3 fuse block and use the bottom fuse slot for your AF.

Last edited by A930Rocket; 11-20-2008 at 12:15 PM..
Old 11-20-2008, 12:12 PM
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My O2 sensor is mounted in the 3" pipe coming out of the B&B muffler on my car.
The wire length from the O2 sensor limits where you can mount the LC-1.

I mounted it on the left side longitudinal under the console with large adel clamps.
I ran all the wires tie wrapped to the high pressure AC line down through the back left corner of engine compartment firewall bulkhead.

The wires continued tie wrapped to that hose up to where the rear 930 fuel pump lives.
On my '87 there was a what appears to be a nice 1" diameter factory hole with a rubber plug in it in the vertcal sheet metal panel just above the back rear corner of the floor pan. It's hard for me to describe that spot better..

Anyway, I ran the wires into the cabin through the rubber plug at that point and the LC-1 wires run out of length on the left rear passenger floor right there.

I spliced new wires in to them to make the power, ground, and gauge wires longer and ran them under the carpet forward between the seats and next to the right side of the auto heat controller and passenger seat rail mount under the carpet.
Then the wires joined up with some other factory wires running forward along the left edge of the front passenger floor pan till they are behind the center console to the left of the passengers feet.
From there they go to 12 volt supply and the G3 gauge.

With the G3, G4, and G5 analog stepper motor gauges, you have the option of connectiong a continuous 12 volt source to the gauge for the purpose of returning the gauges needle to zero after you turn the ignition off.
Otherwise the gauge needle will stay still where it was when you turn off the car.

If you run the car with the wideband O2 sensor not getting 12 volts for it's heater element... then the O2 sensor will be ruined quickly they say.

I have never heard it can be ruined by starting the car with it already up to heat. I suppose if there was water in the muffler and the hot O2 sensor got showered with moisture that could happen.
Old 11-20-2008, 12:34 PM
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Quote:
Originally Posted by A930Rocket View Post
Why not use the hot lead to the CDI? You could run a wire from there to the 3 fuse block and use the bottom fuse slot for your AF.
Electrical line noise is bad for the LC-1, and it's not a good idea taking some voltage and current away fromn the CDI.

Dropping the electrical current available to the CDI will lower the CDI's voltage output to the plugs...

It's so easy to take a few minutes and run the LC-1 and O2 sensor heater element's 12 volt supply line up to the front of the car bundled with the wires for the gauge...

That way you can find a source for clean low noise 12 volts and not compromise the 12 volt supply line for the fuel pumps or CDI ignition.
Old 11-20-2008, 12:42 PM
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