Tachometer...still fails

[gordyzx9r]

I'll start from the beginning.

I have a 6 gauge Stewart Warner instrument cluster that I got from Tom Houser 4 or 5 years ago when he was selling them via his Performance Instruments business.

It was working fine without any issues until recently. I had a bunch of work done to the car by Fred's Turbo Performance and the problem manifested after that.

Here's what happens and what I've done so far to try to fix it.

• The tachometer started going to 0 RPM at 2K to 3K RPM after I had a bunch of stuff installed and some work done.
  
• I took the cluster out, bought a new tachometer, sent off to a place called Williamson's Instruments to have rewired into the cluster like Tom had it (Tom fell off the face of the earth and I can't reach him).
  
• I reinstall the cluster, and it still fails, even with the new tachometer.
  
• I buy a cheap Sunpro tachometer from a local auto parts store and wire it up directly to test out the 'signal' (+ to the fuse box, - to a good ground, and the tachometer lead directly to the pigtail behind the alternator) and it works fine, no failures.
  
• I hook the Sunpro up to the auxiliary harness like my cluster is configured and it works fine there too.
  
• I call Stewart Warner and their tech department is gone (they got rid of it because their tech guys were just calling their distributors for help) and all they can do is send me a free 10K RPM gauge because the 8K has been discontinued.
  
• So, I get the 10K gauge. I also buy two VDO modulators from Casper's.
  
• Just to test out something, I hook a modulator to one of the old 8K Stewart Warner tachometers and it flat lines at 0 as soon as I fire up the car.
  
• I hook up the 10K Stewart Warner with a modulator, and it flat lines too when I fire it up. I take the modulator off, and it fails between 2K to 3K RPM too.
  
• So...the cheap Sunpro tachometer and the Scanmaster signals are never interrupted...but the Stewart Warner gauges seem to be getting interrupted somehow.
  

How?

Where is the tachometer signal coming from that goes to that pigtail by the alternator?

How is the signal routed?

Can the signal be weakened by anything and it's just that the Stewart Warner can no longer pick it up (but the cheap Sunpro gauge can)?

I am so lost what to do now, it's been torn apart in the garage since November now...






The following is everything I had installed at Fred's. I had taken it back to him to see if he could fix it but he couldn't find the problem. I know allot of this is mundane and not related but if someone has installed something once that had a synergistic effect on something else then maybe they had the same issue I did and can shed some light:

Blistein Gas Shocks, Eibach Pro-Kit Rate Springs, Energy Suspension Bushings, Gbodyparts Tubular Upper Control Arms, Gbodyparts Tubular Lower Control Arms, Gbodyparts 15” X 10” Grand National Wheels, Spohn Front Upper A-Arm Mounting Hardware Kit, Spohn Lower A-Arm Mounting Hardware Kit, Body Bolts, GNX Bushings, Dual Air bag kit.

SSBC Quick Change Aluminum Caliper Upgrade Kit, SSBC OE Replacement Rotors, Cotton’s Upgraded Rear Brakes, Aluminum Brake Drums.

Casper’s Headlight Brightener Harness, Casper’s Battery Positive Extender Heavy Duty 102043, Casper’s Negative Battery Cable, Casper’s Fan Harness GN to SPAL Fan, Casper’s Improved Engine Ground Modification Kit, Casper’s Audible Knock Detector.

Classictube SS 2-Piece Tank to Pump Line w/Inline Filter Part No, SS Fuel Injection Feed Line Throttle Body Injection, SS Fuel Rail Feed Line, SS Fuel Rail Return Line, SS Completer Brake Line Kit, Stop Flex Stainless steel braided Hose kit, SS Emission Tubes, SS Fuel Lines (3-piece), SS Transmission Line Kit, SS Vapor Line.

Dual 11-inch (2780 cfm) SPAL Pull Fans w/ Shroud, Aluminum Radiator w/Oil & Trans Cooler, 160° Thermostat, High Flow Water Pump, GM Upper & Lower Radiator Hoses, GM Heater Control Valve, GM 3-Piece Heater Hose, GM Bypass Hose, GM Heater Rail Hose, Steel Braided Hose.

Pat’s Performance 10” Lock-Up Stall Converter & Cotton’s Hardened Stator.

HR Parts Motor Mounts

60 lbs/hr High Impedance Fuel Injectors & Turbo Tweak Chip

MSD Ignition Wires

Steve Monroe 62mm Machine Throttle Body & Matching Plenum

Kirban’s Power Window Motors,

Steadfast Column Guard,

Replaced Rear Main Seal, Replaced Oil Pan Gasket, Replaced Front Engine Cover Gaskets, Replaced Transmission Pump & Gasket, and Replaced Engine Oil & Filter.

 

[MidGaGN]

Man, I was thinking on taking my car to Fred. Would you still take your car to him or do you think it was his fault?

 

[TurboDave]

I'll start from the beginning.

I have a 6 gauge Stewart Warner instrument cluster that I got from Tom Houser 4 or 5 years ago when he was selling them via his Performance Instruments business.

It was working fine without any issues until recently. I had a bunch of work done to the car by Fred's Turbo Performance and the problem manifested after that.

Here's what happens and what I've done so far to try to fix it.

• The tachometer started going to 0 RPM at 2K to 3K RPM after I had a bunch of stuff installed and some work done.
• I took the cluster out, bought a new tachometer, sent off to a place called Williamson's Instruments to have rewired into the cluster like Tom had it (Tom fell off the face of the earth and I can't reach him).
• I reinstall the cluster, and it still fails, even with the new tachometer.
• I buy a cheap Sunpro tachometer from a local auto parts store and wire it up directly to test out the 'signal' (+ to the fuse box, - to a good ground, and the tachometer lead directly to the pigtail behind the alternator) and it works fine, no failures.
• I hook the Sunpro up to the auxiliary harness like my cluster is configured and it works fine there too.
• I call Stewart Warner and their tech department is gone (they got rid of it because their tech guys were just calling their distributors for help) and all they can do is send me a free 10K RPM gauge because the 8K has been discontinued.
• So, I get the 10K gauge. I also buy two VDO modulators from Casper's.
• Just to test out something, I hook a modulator to one of the old 8K Stewart Warner tachometers and it flat lines at 0 as soon as I fire up the car.
• I hook up the 10K Stewart Warner with a modulator, and it flat lines too when I fire it up. I take the modulator off, and it fails between 2K to 3K RPM too.
• So...the cheap Sunpro tachometer and the Scanmaster signals are never interrupted...but the Stewart Warner gauges seem to be getting interrupted somehow.

How?

Where is the tachometer signal coming from that goes to that pigtail by the alternator?

How is the signal routed?

Can the signal be weakened by anything and it's just that the Stewart Warner can no longer pick it up (but the cheap Sunpro gauge can)?

I am so lost what to do now, it's been torn apart in the garage since November now...






The following is everything I had installed at Fred's. I had taken it back to him to see if he could fix it but he couldn't find the problem. I know allot of this is mundane and not related but if someone has installed something once that had a synergistic effect on something else then maybe they had the same issue I did and can shed some light:

Blistein Gas Shocks, Eibach Pro-Kit Rate Springs, Energy Suspension Bushings, Gbodyparts Tubular Upper Control Arms, Gbodyparts Tubular Lower Control Arms, Gbodyparts 15” X 10” Grand National Wheels, Spohn Front Upper A-Arm Mounting Hardware Kit, Spohn Lower A-Arm Mounting Hardware Kit, Body Bolts, GNX Bushings, Dual Air bag kit.

SSBC Quick Change Aluminum Caliper Upgrade Kit, SSBC OE Replacement Rotors, Cotton’s Upgraded Rear Brakes, Aluminum Brake Drums.

Casper’s Headlight Brightener Harness, Casper’s Battery Positive Extender Heavy Duty 102043, Casper’s Negative Battery Cable, Casper’s Fan Harness GN to SPAL Fan, Casper’s Improved Engine Ground Modification Kit, Casper’s Audible Knock Detector.

Classictube SS 2-Piece Tank to Pump Line w/Inline Filter Part No, SS Fuel Injection Feed Line Throttle Body Injection, SS Fuel Rail Feed Line, SS Fuel Rail Return Line, SS Completer Brake Line Kit, Stop Flex Stainless steel braided Hose kit, SS Emission Tubes, SS Fuel Lines (3-piece), SS Transmission Line Kit, SS Vapor Line.

Dual 11-inch (2780 cfm) SPAL Pull Fans w/ Shroud, Aluminum Radiator w/Oil & Trans Cooler, 160° Thermostat, High Flow Water Pump, GM Upper & Lower Radiator Hoses, GM Heater Control Valve, GM 3-Piece Heater Hose, GM Bypass Hose, GM Heater Rail Hose, Steel Braided Hose.

Pat’s Performance 10” Lock-Up Stall Converter & Cotton’s Hardened Stator.

HR Parts Motor Mounts

60 lbs/hr High Impedance Fuel Injectors & Turbo Tweak Chip

MSD Ignition Wires

Steve Monroe 62mm Machine Throttle Body & Matching Plenum

Kirban’s Power Window Motors,

Steadfast Column Guard,

Replaced Rear Main Seal, Replaced Oil Pan Gasket, Replaced Front Engine Cover Gaskets, Replaced Transmission Pump & Gasket, and Replaced Engine Oil & Filter.

The tack wire just behind the alternator comes directly from the coil module, pin E, which I think is fifth away from the firewall.

I could be wrong, but if I remember the white wire goes from the coil module out to the connector and then from there back into the dash harness somewhere.

 

[gordyzx9r]

Man, I was thinking on taking my car to Fred. Would you still take your car to him or do you think it was his fault?

I don't think it was his fault, I had allot done at once. Also, the car was in storage from '04 till recently while I was overseas. During that time, the Viper alarm went bad and freaked out (which was not fun for the the people where it was stored when the 3 pain generators started going off). My dad took it too an alarm shop in CA that claimed the business that installed it in TN didn't know what they were doing so they 'rewired it'. I didn't get a chance to drive the car more than a few times before taking it to Fred so I don't know for sure if the tachometer was failing before I even brought the car to him. There were a couple of things he did that I wasn't 100% happy with, but I just brought the car back and he was able to rectify it. Unfortunately, he was not able to fix my tachometer issues.

The tack wire just behind the alternator comes directly from the coil module, pin E, which I think is fifth away from the firewall.

I could be wrong, but if I remember the white wire goes from the coil module out to the connector and then from there back into the dash harness somewhere.

That's kinda where I'm at now...I started thinking that the Viper is the culprit and what I found was that there is a purple wire coming from the firewall that is spliced to the purple/white wire of pin C of the ignition module. I was able to download the installation instructions for the Viper 791XV and it says that a violet/white wire from the Viper module should go to the tachometer lead of the ignition model. I think they screwed up the install right there and read the instructions backwards. I un-spliced that wire but I'm still having the same problem.

So I'm gonna have the alarm system completely removed and go from there. I have a feeling that my ignition module is screwed up too now. I sent the tachometer to someone to test on their car to see if the tachometers are even any good still to rule them out.

I hate gremlins..

 

[ELLISDALLASWE4]

Make sure that no one has plugged the two wires just behind the alternator together... you probably know that but maybe someone was new at the shop. I see those two plugged into each other every once in a while..that does make tachs jump.

 

[krazy86t]

I have a similar problem - although different reasons (?) - tach is eratic and never measures anything close to accurate. SunPro II, green wire from tach is connected to 5th from firewall white wire on connector to coil module. The connection to the tach was done at coil module by stripping some insulation from the coil connector wire - kind of a hack job.

Is this the right connection point? What is the other "wire behind the alternator?" Also checking bad ground - unit is grounded to dash mounting brackets.

car is a t-type, no stock tach. thx!