QwkTrip

iTrader: (22)

I've heard that you can remove the computer and the gauges and chassis wiring will still work fine. So as part of my motor swap on my '89 Firebird I just removed all wiring that came from the computer. Looking at what I've got left over I noticed I've got one problem (note this is an assumption because I have not connected power yet):

I now have only one wire to my temperature sending unit and it goes to the firewall bulkhead next to steering shaft. I assume those wires go to the gauges. My other assumtion is that the wire I'm missing is a 5-volt source from the original computer which is now gone. I need to know if this is true in order to know whether or not I need a 5-volt or 12-volt source to drive my temp gauge. Could someone explain how the original wiring drives the temp gauge in my dash?

Thanks.

Vader

QT,

This is from recollection, so don't hold me to it as if it were Gospel;

As I recall, ALL standard instruments use a 12VDC source to the heater element or d'Arsonval movement. The instument heater or open end of the movement winding is grounded through the appropriate sensor - in this case a 100K-0 ohm resistive element in the gauge CTS. This is true for oil pressure, coolant temperature, and fuel level instruments.

Of course, if you have the Grand Theft Auto (GTA) with the "Star Wars" digital cluster (no wonder the Empire lost the war with that kind of equipment) all bets are off. The signals for the digital cluster are dertived from the ECM in most cases, so diagnosis is a PITA without a digital probe and interface to the ECM.

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Later,
Vader
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"Get UP - Drop the bombshell!"
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johnsjj2

Okay, I have a question to add. I just swapped a carbed motor in my 91Z. I took out the computer, and the related harness. The only wires I cut going to the fuse block on the drivers side, was a pink with black tracer, and an almond colored wire, and a tan wire. I found out later that the tan wire was for the fuel pump. I put 2 relays in, one for the pump, and 1 for the fans with a breaker. I have no gauges at all. The speedo, I didn't expect to work, along with the oil pressure gauge, but the tach, fuel level, volts, and water temp are not working. I have checked all the wiring to the appropriate sensors, all is good. I did move the temp sensor from the drivers side head on the 305, to the intake on the 350. Any ideas why my gauges are blank.

Thanks,



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Joshua Johnston
1991 Z-28
Flowmaster
K&N
305 / 5spd. (Temporary)
Soon to have:
350, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust, T&R Motorsports custom air intake

johnsjj2

Maybe I should add that I also removed the buzzer from under the dash. I didn't think that would affect the whole gauge cluster though. Any ideas???

Thanks,


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Joshua Johnston
1991 Z-28


350, T-5, K&N, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust,Dynomax Bullet Mufflers, T&R Motorsports custom air intake

deadbird

Assuming you cut the wire inside the car, you may have inadvertantly cut the power wier to your gauges. The ECM & gauges both share (but don't use)the same color wire.

johnsjj2

deadbird,
Thanks for the reply. I found out last night that somehow I popped the 10 amp fuse for the gauges. As much probing as I did for the ignition, it wouldnt suprise me if I did it then. I replaced the fuse and all is well again.

Thanks,


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Joshua Johnston
1991 Z-28


350, T-5, K&N, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust,Dynomax Bullet Mufflers, T&R Motorsports custom air intake