krickmann

I'm installing an air/fuel gauge and a boost gauge. Had a couple questions from those who know or have done this already. And, yes, I did a Rennlist search already.
The A/F meter O2 wire goes to pin 24 on a 1986 also? The red wire needs full 12 volt power and not from a light dimmer source, right? The ground can just go somewhere near the gauge and not necessarily to the pin 28, right?
The boost gauge red wire should be to a light dimmer source. Which is most easily accessible?
Thanks in the meantime!

jason952

the little wire that runs to the ashtray light also dims, that's the one I used. if your doing a-pillar gauges, that doesn't help ya.

j

sybelix

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by jason952:
<strong>the little wire that runs to the ashtray light also dims, that's the one I used.
j</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">yup, same thing here

Wormhole

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> The ground can just go somewhere near the gauge and not necessarily to the pin 28, right?
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">A good ground is critical for a proper operation. After struggling for a good source I eventually went strait to the battery (recommended).

Danno

Krickman, the O2-sensor signal comes in on a coaxially shielded cable, so make sure you do not use vampire taps on that cable; you'll short out your O2-sensor.

I've got a procedure with photos on my <a href="http://members.rennlist.com/951_racerX" target="_blank">951 RacerX website</a> under the ARM-1 Installation section. You can tap into the inner conductor of the coax cable after it's split from its shielding inside the DME connector.

As for grounds, there should be zero difference between the grounds at the DME and at the battery. If there IS a difference between ground potentials at the DME & battery, then you've got a bad ground cable somewhere. By hooking up the O2 gauge to a different ground than the DME, you'll be measuring a different voltage-potential coming out of the O2-sensor than what the DME sees, leading you to incorrect readings. So, if you find there's a difference by hooking up the gauge's ground directly to the battery, then don't cover up that problem, fix the ground cables and use the DME's ground to keep the gauge accurate.

krickmann

Thanks guys! I will run both the violet and black wire to the DME. Can anyone who's installed in the A pillar help with the other questions?

rcldesign

In an ideal world there is no difference between the DME ground and the battery negative. But, this isn't exactly true. Unless the cable you have going from the battery to a chassis ground is a superconductor, it will have resistance. Interestingly, the DME grounds itself on the bell housing. This is because most all the sensors also ground themselves on the block. Why do you think the ARM-1 has both a ground wire and a signal ground? The ground wire can go to the battery, or some other grounding point. But the signal ground should go to the O2 sensor, or perhaps the engine block (though in the case of the stock 3-wire sensor, it doesn't exactly matter).

All in all, the ARM-1 really only has .1V resolution anyway, so its not like you're going for accuracy here.

streckfu's

I tapped into the wire that controlled the instrument lighting for dimming. I'll have to look up which one to refresh my memory.

Daniel