Ron Francis Wiring with Speed Hut gauges

[mrglaeser]

This is a dumb question but better to ask than see smoke escape from electrical I figure.

-I Purchased Speed Hut Gauges directly from Speed Hut for reasons
-I have the Ron Francis wiring harness

Wiring the the two seemed straight forward but here is my question. The Speedhut gauges each came with a lead and a sensor. The wiring is usually just two wires the a signal and ground from the sensor to the switch.

My plan was to cut the sensor connector from the Speedhut wiring for each gauge and just splice them into the RF harness in the engine bay. However I noticed the grounds on the RF harness are not labeled for each sensor. There are 3 grounds in the engine bay labeled simply ground and individually labeled signal wires for Oil Pressure, Oil Temp, and Water Temp each. When I used a multimeter to trace the 3 grounds they seem to be connected because I see continuity between all three grounds and all the ground pins in the weather tech connector in the cab. All the Ground pins in the cab seem to have continuity to all three grounds in the engine bay.

So if I'm thinking about this right, the RF harness uses common ground for the gauge's signal ground and sensor's ground. Where if I used the Speedhut wiring the sensors ground to the engine and then send a ground to the gauge.

Does it matter? Is it ok to wire the Gauges Directly to the RF Dash Harness and then the sensors to the RF Harness in the engine bay? I hopes so because I already wired the dash harness.

Bonus question. The Speedhut Connectors and RF Connectors that plug into the gauges have the wires in a different order in the 3 pin connector. IE one uses the the left side and the middle connector and the other uses both outside connectors. The Signal wires always seem to match but the ground is in different locations. I made a bad diagram - see below. I just cut the connectors off both the Speedhut and RF wiring and then splice the speed hut connector to the RF Harness (with the exception of the Oil Pressure sensor which I ran the Speendhut cable into the Engine bay as it had 3 wires instead of the 2 that the RF harness had for that gauge). Does anyone see a problem with this method of combining the harnesses?

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-HXdb8t8/0/89510b4f/L/RF%20v%20Speedhut%20Connector%20wiring-L.png (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-HXdb8t8/A)

Also here is pic of the Speedhut instructions. See under Temperature Gauge it shows a White Signal and Black Ground and the cable goes like that directly to the sensor
https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-2Lf26FM/1/eedd21c7/X2/20240101_150152-X2.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-2Lf26FM/A)

[MB750]

My main beef with the RF harness was that it's built for multiple applications. Not just other vehicles, but older versions of the Roadster from FFR. There's connectors in the dash harness that use the OEM harness to connect to sensors, but there's paralleled connectors for going straight to the sensor.

After I noticed this I gutted my dash and engine bay harness from all the useless wiring, then took sensors directly to gauges. This cleaned a lot up. Some sensors have one wire (and use engine block as the ground), and some need the ground wire along with the sensor wire. Just depends on the type of sensor.

Hopefully this helps. I also had to relocate the fuel level wire within the connector, see here: https://thefactoryfiveforum.com/showthread.php?46595-Fuel-Gauge-Calibration-Issues

[rich grsc]

Why would you buy a set of Speed Hut gauges then not use the wiring they send? all the gauges get daisy chained together then have a common power, ground and switched wire, one set of wires for connection.They have their own cable for the engine sensors, plug & play

[phileas_fogg]

I used the Speedhut sensor wires instead of the RF wires (like what Rich suggests). I seem to recall completely eliminating the RF sending units harness by doing so, plus maybe a couple of other wires. Using the Speedhut wiring instead of the RF wiring let me run the sensor wires where ever they best suited my purpose (the oil pressure wire is routed completely separately than the water temperature wire for example). To keep things straight behind the dash, I used a sharpie to mark the connectors with different symbols. The male & female connectors for gauge one is a red triangle, for gauge two is a green circle, for gauge three is a black square...


John

[mrglaeser]

Why would you buy a set of Speed Hut gauges then not use the wiring they send? all the gauges get daisy chained together then have a common power, ground and switched wire, one set of wires for connection.They have their own cable for the engine sensors, plug & play

I was hoping for easier time wiring. Changing the ends on the RF harnesses seemed a lot easier and cleaner looking than running four separate wire bundles into the engine bay and one back to the fuel sender. I also made an assumption and should have looked at the schematic that the RF harness had dedicated grounds for each gauge like the Speedhut cable bundles. Again I just didn't think gauges would be wired that differently.


I used the Speedhut sensor wires instead of the RF wires (like what Rich suggests). I seem to recall completely eliminating the RF sending units harness by doing so, plus maybe a couple of other wires. Using the Speedhut wiring instead of the RF wiring let me run the sensor wires where ever they best suited my purpose (the oil pressure wire is routed completely separately than the water temperature wire for example). To keep things straight behind the dash, I used a sharpie to mark the connectors with different symbols. The male & female connectors for gauge one is a red triangle, for gauge two is a green circle, for gauge three is a black square...


John

John - I did run the Oil Pressure line from Speedhut because it has an extra signal wire than what is present in the RF. I also used the two daisy chains for needle and back lighting attaching them to the dash harness grounds, gauge power, and dash lighting leads.

[rich grsc]

It doesn't get much easier than using the Speed Hut wiring. A couple of connections behind the dash, nothing to change or rewire in the engine compartment. I used nothing from the wire harness except for a power wire and a light wire for the gauge lights.

[jgray]

I was hoping for easier time wiring. Changing the ends on the RF harnesses seemed a lot easier and cleaner looking than running four separate wire bundles into the engine bay and one back to the fuel sender. I also made an assumption and should have looked at the schematic that the RF harness had dedicated grounds for each gauge like the Speedhut cable bundles. Again I just didn't think gauges would be wired that differently.



John - I did run the Oil Pressure line from Speedhut because it has an extra signal wire than what is present in the RF. I also used the two daisy chains for needle and back lighting attaching them to the dash harness grounds, gauge power, and dash lighting leads.

I'm planning on doing the same as you. I am a novice builder but am fairly experienced with soldering and wiring (built a lot of RC race planes with intricate electronics) spent the last 4 months redoing most of the RF wiring, getting rid of a lot of wires, shortening many and soldering directly onto switches and adding Weather Packs so I can remove my custom switch panel. I have rewrapped most everything and use a lot of tie downs etc. Anyway, I prefered the idea of using the RF harness because it reduced wiring.

You do raise a good point about the grounds. From what I have been reading electronics are sensitive to the momentary high voltage (low amps) that occurs when the coils in relays collapse when they are turned off - I have seen articles on isolating the grounds of electronics from regular electrical (fuel pump, cooling fan, ...). This could be overkill. I tend to go down rat holes when I start learning something new. Having said that, the three-in-one Tremec T56 reverse lockout/speed-sensor/reverse-light gadget (from MDL) that I just received has specific instructions to run its ground directly to the battery - it has blue tooth and other electronics in it that connects to an app that allows you to configure the speed that lockout occurs along with other stuff. Not sure if the Speedhut gauges are sensitive in the way they ground; I'm guessing they are not, otherwise the instructions would say so, and there would be people on here more experienced than me warning about it.

So, I plan to do the same as you and expect it to work just fine!

[mrglaeser]

I'm planning on doing the same as you. I am a novice builder but am fairly experienced with soldering and wiring (built a lot of RC race planes with intricate electronics) spent the last 4 months redoing most of the RF wiring, getting rid of a lot of wires, shortening many and soldering directly onto switches and adding Weather Packs so I can remove my custom switch panel. I have rewrapped most everything and use a lot of tie downs etc. Anyway, I prefered the idea of using the RF harness because it reduced wiring.

You do raise a good point about the grounds. From what I have been reading electronics are sensitive to the momentary high voltage (low amps) that occurs when the coils in relays collapse when they are turned off - I have seen articles on isolating the grounds of electronics from regular electrical (fuel pump, cooling fan, ...). This could be overkill. I tend to go down rat holes when I start learning something new. Having said that, the three-in-one Tremec T56 reverse lockout/speed-sensor/reverse-light gadget (from MDL) that I just received has specific instructions to run its ground directly to the battery - it has blue tooth and other electronics in it that connects to an app that allows you to configure the speed that lockout occurs along with other stuff. Not sure if the Speedhut gauges are sensitive in the way they ground; I'm guessing they are not, otherwise the instructions would say so, and there would be people on here more experienced than me warning about it.

So, I plan to do the same as you and expect it to work just fine!

jgray - I just got off the phone with Speedhut. They said that in the past they did have performance issues with common ground and that is why they now use isolated grounds. They further suggest that I use their wiring not the RF wiring. So I guess I'm going to at a minimum rewire the oil and water temp gauges and diet them from the Harness to make room for SH wiring. I need review the wiring for the tach and fuel sender. The fuel sender will be the worst to run as I have a pretty aggressive drop trunk already installed. I do have an access panel but running the wires will be a pia. So that one I might test out as is during go-karting. I also need to break open the Sniper guides and see if I need to run any of the RF EfI wiring to that setup.

Plug and play harnesses aren't so plug and play.

[jgray]

jgray - I just got off the phone with Speedhut. They said that in the past they did have performance issues with common ground and that is why they now use isolated grounds. They further suggest that I use their wiring not the RF wiring. So I guess I'm going to at a minimum rewire the oil and water temp gauges and diet them from the Harness to make room for SH wiring. I need review the wiring for the tach and fuel sender. The fuel sender will be the worst to run as I have a pretty aggressive drop trunk already installed. I do have an access panel but running the wires will be a pia. So that one I might test out as is during go-karting. I also need to break open the Sniper guides and see if I need to run any of the RF EfI wiring to that setup.

Plug and play harnesses aren't so plug and play.

Thanks for sharing the information! I'm glad I saw your post. I am still at the point where I can change things around pretty easily, but everytime I think I am done with wiring something comes up! Like many things, as you learn more you realize there is so much more to learn! I had been thinking about isolating the ground for my display mirror also and think I will go ahead and do that. In my C8 Vette which has display mirror I can see that if reboots/refreshes occasionally and am now wondering if this is an interference or grounding issue!

[erniek70]

I have been chasing an issue for a while...and I am now wondering if the ground is suspect. My fuel gauge reads low when there is a large draw on the elctrical system lights and/or engine cooling fan. On the back side of the speedhut fuel gauge, there is a paired set of black wires....one plain black, one black, with white dashes. Which one is the ground for the signal/needle?
216485

[BrewCityCobra]

I'm not sure if this is the answer you are looking for, but I found the best way to wire the Speedhut gauges (I also bought mine directly from Speedhut separate from the kit) is to just use the wiring materials provided by Speedhut for the sensor leads and only rely on the RF harness for the "BRN-GAUGE FEED," "WHT-DASH LIGHTS," and "RED-SPEEDO/CLOCK MEMORY" feeds. The exception being the Fuel sender feed. The "gauge" portion of the RF harness is pretty awkward and bulky to say the least so I don't know that it really provides much, if any, advantage to utilize the sensor aspect of the build but does require a ton of work to splice in the necessary connectors. Just my .02.

[gbranham]

I'm not sure if this is the answer you are looking for, but I found the best way to wire the Speedhut gauges (I also bought mine directly from Speedhut separate from the kit) is to just use the wiring materials provided by Speedhut for the sensor leads and only rely on the RF harness for the "BRN-GAUGE FEED," "WHT-DASH LIGHTS," and "RED-SPEEDO/CLOCK MEMORY" feeds. The exception being the Fuel sender feed. The "gauge" portion of the RF harness is pretty awkward and bulky to say the least so I don't know that it really provides much, if any, advantage to utilize the sensor aspect of the build but does require a ton of work to splice in the necessary connectors. Just my .02.

Exactly what I did with my custom Speedhut gauges.