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S5 turbo swap -> vacuum/boost gauge not working

Old 09-03-12, 02:03 PM
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S5 turbo swap -> vacuum/boost gauge not working

Car - 89 GTU

I have swapped this car to turbo and manual transmission. The car used to be automatic. I am not getting any reading from the vacuum/boost gauge in the stock cluster. I know how much better an aftermarket boost gauge is but want the stock one to work too. I have searched but have not found anything specific to my application.

I am using all USDM S5 (N370) electronics. This includes the ECU, AFM, MAP sensor. The car runs and drives fine. I know I have a good vacuum source connected to the MAP sensor. I have tried the auto and manual trans gauge cluster sub-harnesses. I am using a NA EM harness. From looking at the wiring diagrams, the cluster sub-harnesses look the same from NA to turbo.

Any help would be appreciated. Thanks
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Old 09-03-12, 02:05 PM
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the n/a cluster had no pinout for a boost gauge, you will have to move wires around or run a new one to the junction behind the passenger kick panel.
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Old 09-03-12, 02:11 PM
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Originally Posted by RotaryEvolution View Post
the n/a cluster had no pinout for a boost gauge, you will have to move wires around or run a new one to the junction behind the passenger kick panel.
can you elaborate? i was hoping i could move a wire or two around from the now unused volt gauge wiring.
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Old 09-03-12, 02:23 PM
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maybe satch can help with the wire pinouts, it's been a few years and i only have experience with the S4 on a turbo swap with cluster.

there will be a wire from the boost sensor to that kick panel connector, the wiring for the round connectors at the cluster have a few different wires, one now leads to the boost gauge so will need that moved around to meet up with the wire at the kick panel connector.

all you need to do is transpose the n/a cluster connector over the turbo one, and then the XD-1/2(i forget which) at the kick panel which i believe originally was the alternator charge wire on the n/a harness, the turbo harness has different pin locations so the wires will be slightly different if you used the turbo harness and it should be in the correct location already.

cliffnotes: go into the manual and pull up the wiring diagram, pull the diagram of the cluster for n/a and turbo and the engine harness to front main harness(dash harness) for n/a and turbo. compare the 2 at both ends and move the wires around or make a new one.

Last edited by RotaryEvolution; 09-03-12 at 02:27 PM.
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Old 09-03-12, 02:36 PM
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Pin 2H at your ECU should have a Green/Yellow wire. This wire needs to be tapped into and run towards the Boost Gauge.
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Old 09-03-12, 02:54 PM
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perfect. is there a way to reuse the stock wiring or do i need to run a new wire?

also, when i look at the diagram for the turbo gauge cluster, it shows the volt gauge and no pressure gauge.

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Old 09-03-12, 03:01 PM
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I use the same site for diagrams so this diagram is not that much help since it shows a volt gauge for both NA and turbo which we know is incorrect. The wire that you tap into will be new at pin 2H but it can be run to where the original alternator wire is as Karack mentioned and then picked up from there as it then runs to the gauge.

Correct S5 Turbo diagram in this link.

https://www.rx7club.com/attachments/...olsystem12-jpg

Last edited by satch; 09-03-12 at 03:06 PM.
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Old 09-03-12, 03:06 PM
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i can run the wire from 2H directly to the back of the cluster right? to the BR/R wire?
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Old 09-03-12, 03:28 PM
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Originally Posted by 87 t-66 View Post
i can run the wire from 2H directly to the back of the cluster right? to the BR/R wire?
That makes some sense but if you could find an accurate diagram to compare NA from turbo it would help you know whether your above statement is correct.
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Old 09-03-12, 03:34 PM
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i think it's the only diagram. at least that i've seen. i'd rather tap into the cluster wiring than the alternator wiring. it would also be a much shorter wire that would need ran. as far as i know, the only difference in clusters is the volt/pressure gauge.
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Old 09-03-12, 06:14 PM
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what wire at the alternator harness would i need to tap into if i didnt use the gauge cluster wiring?
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Old 02-16-15, 01:59 AM
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Hey I have had my car for a while and always wanted the stock one to some what work. I saw your thread about it and was wondering if you ever figured it out. If you did it would be great if you could let me know what you did. Thanks.
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