ChicagoTransAm

OK, as I have been removing/installing my gauges 100 times over, I have realized that full power failure to the gauges results in a test sweep on connection. Anyone have a pinout on the harness? I would like to rewire the main power to the ignition switch to get a sweep on startup.

This might be a lil' "ricey" sounding...but well...I dig it anyhow (and yes, I know I will lose my trip odo on every startup. Whooopty doo

WhiteBird00

iTrader: (4)

It can't be removing power that triggers it because there is no power to any of the gauges when the ignition is off. It must be something to do with disconnecting the data link connection between the instrument cluster and the PCM. This is handled by the gray wire in pin B6 of the instrument cluster connector. I would be very careful about modifying this connection because it carries class 2 serial data - not just voltage as in most circuits. You could possibly hook up a relay to break the circuit when the ignition is shut off.

ChicagoTransAm

There IS voltage running to the gauges while the engine is off. When I plug the gauges in (ign off) ...this is when they sweep.

WhiteBird00

iTrader: (4)

Sorry, but the electrical schematics in the service manual show only two power connections to the instrument cluster (other than for illumination and indicator lights). One is from the GAUGES fuse and is active in RUN and START while the other is from the starter circuit and is active only in START. Neither would be providing power when the ignition is off.

Now, the PCM does have constant (battery) power and it has that class 2 serial data connection to the instrument cluster so maybe that is what causes the sweep when the cluster is plugged in.

ChicagoTransAm

With the SAE J1850 (class 2) I am showing a possible output voltage of 5.25vdc. If in fact there are no other voltage sources, this must be where it is coming from. I think it uses a 1.?? vdc pulse for other communications..but hmmph...looks like I need to do some more reading.

I think that I might end up going the route you were talking about though. Using a 12v source on the pull side of a relay to make a connection with the serial connector.

Can you post a picture of the schematic? I'd like to know the full pinout.

LS1_SS

iTrader: (127)

theyre supposed to, whats the problem?

WhiteBird00

iTrader: (4)

Here you go... (sorry about the size - I didn't have time to play with it much)





Note: Before you start accusing me of not being able to read... the orange wire in A10 that's listed as fused battery feed has nothing to do with the gauges - it's power for the Security indicator light.

ChicagoTransAm

That would be B3 though wouldn't it? Can't see that they would use a full battery connection to light up one LED and then the PCM to power up a full gauge sweep.

I suppose the only way to tell for sure would be to pull apart the cluster again and look at where the traces are going on the board

WhiteBird00

iTrader: (4)

The security light has 12V battery feed at all times on circuit 640 through A10 and the ground goes to the BCM on circuit 728 through B3 (the security light "input"). The BCM controls when the light illuminates by enabling or disabling the ground.

ChicagoTransAm

Cool...so it looks like I'm back to disconnecting the serial then

BigSteele

iTrader: (17)

damn my gauges reset/sweep everytime I start it up and I want to make it stop

94Camaro

iTrader: (1)

Does your car sorta 'drag' when you start it up as well? My battery was about dead and so it was slow to crank(obviously), but the gauges always did the sweep on startup and the trip counter reset itself everytime the car was turned off. Dropped in a new battery and the gauges don't sweep anymore and the counter doesn't reset itself. Might help ya.

ChicagoTransAm

Make ya a deal then...send me your broken gauges and I'll send you my "non sweepers"

ChicagoTransAm

And FWIW, when I disconnect my gauges entirely..it doesn't reset the trip odo.