Need some help with my FAST

[Brassmonkey]

I am having an electrical issue after having a FAST ecm installed on my Sy. The speedo reads 30 mph when first started up and idling. I can turn on the lights and the speed goes to 20. I can then plug my power inverter into the cig lighter and the mph goes to 10. Then I can plug in my radar detector and the mph goes to zero. Has anyone that has installed a FAST in their SyTy had any electrical issues, or is this just a coincidence and I have other issues? I had my speedo checked and it is working fine.

 

[RealFastV6]

Are you saying that the Speedometer is reading 30/20/10 or are you saying that the Speedometer is reading correctly but the FAST is reading 30/20/10?

 

[Brassmonkey]

I am saying the speedo is reading 30/20/10. I don't know how to check the speed readout in the FAST.

 

[RealFastV6]

Your Speedo ground comes from a black cable that goes through the C100 connector that goes to the front drivers side intake bolt. It's shared with all the other things you mentioned.

Location is C2 in the C100 Connector.

I'd start with making sure that's there.

Is this a Classic FAST or an XFI? Is it the adapter to the factory harness or a rip and replace of the factory harness?

 

[Brassmonkey]

So RealFastV6, you are saying that it is just a coincidence that this happened when the FAST was installed and I have other issues? It is a FAST XFI 2.0. Also, it is the factory harness, re-pinned for the FAST. Do you have a FAST installed on your SyTy?

 

[RealFastV6]

I wouldn't call it a coincidence - there was a significant amount of re-wiring that went on to install the FAST and there's a good chance that something got messed up or missed in that rewiring.

The speedo only has three inputs.

There's a Ground. (Let's check that first)
There's a 5V reference.
There's a Signal from the DRAC.

Yes, XFI 2.0 in my Syclone.

 

[Brassmonkey]

Thanks for the info, the ground will be checked.

 

[RealFastV6]

Any update?

 

[tunerpike]

The Ground you are looking for is G109, originally it was located on front of the intake driver side.. However, if that ground isn't hooked up most things inside the cab want work.. for instance, Ashtray Lamp, Radio, Cig Lighter, Heater Lamp, Safety Belt Buzzer, Panel and Interior Lamp.. Etc..

Does your speedo working at all? Are you using the stock speed sensor from the transfer case or are you using an output from the Fast?

 

[RealFastV6]

It's a thought - but I can't see how the signal being messed up would show different MPH when the ground is impacted by different things being plugged into the cigarette lighter. I'm thinking more like poor ground circuit is gaining voltage +1V +2V, etc which is modifying the readout because the speedo references against it.

The FAST shouldn't be outputting to the Speedometer - it should be the DRAC directly to the speedometer.

 

[Brassmonkey]

I had the speedo tested and no problems were found, but not much else has been checked yet. I will probably know more after the new year. EVERYTHING was working fine before the FAST install and now the SPEEDO is reading erratically.

 

[Brassmonkey]

All wires, grounds and power, going to the FAST and gauge cluster have been checked, with no joy. What is the voltage suppose to be going to the DRAC? Does the FAST have an adjustment for speedo readings?

 

[Brassmonkey]

Finally got to do some more work on the Sy and I think the DRAC is bad. Does anyone have one, the broadcast code is AGS and the part # is 25073966.

 

[Brassmonkey]

Here's a BIG thanks to RealFastV6 for the help fixing my Sy.

 

[atkonkler]

Here's a BIG thanks to RealFastV6 for the help fixing my Sy.

How lond did it take for you to install the Wiring for the fast 2.0 ...ive had one in the box with a harness also just chilling. was it worth it do your think?

 

[Brassmonkey]

How lond did it take for you to install the Wiring for the fast 2.0 ...ive had one in the box with a harness also just chilling. was it worth it do your think?

If you have a plug and play harness, it will take about 5 minutes to install the fast. What kind of harness do you have?