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What does "Ignition" mean for Instrument Cluster Wiring? by sjmaye
Started on: 05-21-2020 06:09 AM
Replies: 5 (119 views)
Last post by: theogre on 05-23-2020 11:54 AM
sjmaye
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Report this Post05-21-2020 06:09 AM Click Here to See the Profile for sjmayeSend a Private Message to sjmayeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am troubleshooting my instrument cluster. The service manual is good, but I thought a photo of the back of the instrument cluster would help me more. I am tracing the connections. The manual indicated some contacts as "Ignition". I am no electrician. In working on cars I am used to +12v or ground. These idiot lights need +12V on one side and ground (I assume) on the other. Can someone tell me why the manual calls these contacts, "Ignition"?
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Cajun
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Report this Post05-21-2020 07:12 AM Click Here to See the Profile for CajunClick Here to Email CajunSend a Private Message to CajunEdit/Delete MessageReply w/QuoteDirect Link to This Post
12 volts is applied when the ignition switch is turned to the "ON" position.
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sjmaye
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Report this Post05-21-2020 07:15 AM Click Here to See the Profile for sjmayeSend a Private Message to sjmayeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Cajun:

12 volts is applied when the ignition switch is turned to the "ON" position.


So, in the case of the SES light. Does that mean the SES contact is the ground and the "Ignition" contact +12V?
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Gall757
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Report this Post05-21-2020 09:33 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by sjmaye:


So, in the case of the SES light. Does that mean the SES contact is the ground and the "Ignition" contact +12V?


Yes.

Assuming you are looking at the connector tabs at the lower left....the SES label is the trace to the SES bulb (ground side), and the 'Ignition' is switched 12 v. to the bulb (pos. side). The circuit is completed by the ECU grounding the SES trace. The 2 tabs are opposite each other on the connector, but they don't need to be. The printed circuit layout made that happen.

[This message has been edited by Gall757 (edited 05-21-2020).]

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sjmaye
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Report this Post05-22-2020 05:47 AM Click Here to See the Profile for sjmayeSend a Private Message to sjmayeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:


Yes.

Assuming you are looking at the connector tabs at the lower left....the SES label is the trace to the SES bulb (ground side), and the 'Ignition' is switched 12 v. to the bulb (pos. side). The circuit is completed by the ECU grounding the SES trace. The 2 tabs are opposite each other on the connector, but they don't need to be. The printed circuit layout made that happen.



Sort of weird from my limited electrical background, but it makes sense the way you describe it. Thanks!
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theogre
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Report this Post05-23-2020 11:54 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could simply read http://www.fiero.nl/forum/Forum2/HTML/138175.html for most of this...

Because the picture was shot "wrong," the left C2 plug hole doesn't line up easy w/ some traces to follow them.

The other ignition on C3 is for alt bulb to turn on the alt plus alt warning if alt has problems.
Plug connects both by jumper there to design board easier.

Ignition on C2 is power for gauges and some bulbs.

2 blank bulb holes are "Spares bulbs" and should have sockets at minimum to block light leaking.
Fiero Designers had something planed for those but canceled for whatever reason. 1 N/U pin is ground to one when on. GM cut contacts to the other light to repurposed to run OP gauge.
(Even 84 has both listed as Spares bulbs but have board contacts for them going nowhere after the plug.)

Temp/fuel Gauge Clips are power, ground and "signal" for top, reverse order for bottom.
Tach clips OP, Power, Tach on top, ground at bottom. This dash must be for GT because never had OP clip. (I think 84 Dash "board" and back plastic are different and can't take OP clip.)
(84 use same warning bulb for Temp and OP)

Note that those clips are just 1 reason the dash gauges lie to you. Oxide "Rust" makes problems both on the "board" and on gauge "bolts" to plug into the clips.
Gauges have resistors bolted to back of them gets crap or loose nuts cause same problem.

Oddly the 84 docs have Illumination lights shown for temp/fuel gauges but ignore them for later years and why the other page I had to add O & P bulbs.

------------------
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[This message has been edited by theogre (edited 05-23-2020).]

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