Wiring 2 Pyro's to 1 guage!

[kollmer]

Can anyone assist? What would be the 'best' way to wire 2 pyro's to 1 gauge with a switch so I can alternate between a pre- and post- turbo pyrometer.
And while I'm here is there an easy way to run the wires down the A pillar. I think I saw here somewhere that the dash rolls down? Or just feed them underneath.
Thanks for any suggestions. #ad


------------------
2001 2500 ETH/DEE all Black short bed, Rhino lined, Mag-Hytec rear cover, Amsoil throughout including Amsoil Dual Remote Filter System using RemoteBracket mounting system. Everthing else but leather.
http://sites.netscape.net/remotebracket/homepage

 

[illflem]

You will need a double pole double throw switch (DPDT) The wire terminals on the switch can't be the plated silver colored type,the dissimilar metals,copper wire,nickel switch will produce juice and throw the readings off. You are better off to use a switch with solder connections,you will be able to get a smaller one of this type anyways. Run the wires from the gauge to the center two terminals,the two wires from each sender to opposite ends of the switch,observe polarity the entire time. You're set. I've just ran wires though the opening in the dash at the bottom of the A pillar when it's removed. A coat hanger or stiff wire will make it easier to feed the wires,just push the hanger in from the top and tape your gauge wires to it. It's also easier if you pull all your wires and tubing though at the same time.

 

[JR2]

I had a Westach gauge catalog around here somewhere, but it has a switch for doing just that. It was for aircraft use, but it would work just fine. If you go to there website you can request a catalog.

------------------
John D. Rathert Jr.
*************************
01 2500 Forrest Green Sport SLT+ QC LWB 4x4 Auto 3. 54 rear end with all options avail. DC Nerf Bars, DC Grill Guard, DC mud flaps, Line-X bed liner, Leer 160XL Topper, Power Edge, EZ Edge, SPA Boost/EGT Gauge on pillar mount, DDT's tc/vb combo, 275 RV injectors, DD 4" Exhaust and a KN RE0880 where the air box use to be. New turbo (HX40), SS fuel lines and bigger injectors in planning stages... . See My Truck, Dads truck: 98. 5 3500 SLT QC LWB 4x4, Brother Truck: 92 W250 SLT CC LWB 4x4 (Dads old truck) Winter fun - 2000 Skidoo Summit 700
*************************

 

[Johnboy3]

I was just looking at an Autometer catalog the other day. They have a box that you can plug two thermocouplers into and switch between them. There were a whole bunch of settings and adjustments on the box. I guess for max egt's and warning lights and such.



------------------
1997 F-250, 4x4, PSD, intercooler, 4" exhaust, dual stage propane injection

 

[Cooker]

I called Westach today to ask about their switch and the gentleman informed me to go to Radio Shack and get a switch. I asked him if I needed to get anyhting special and he said no. So this makes me wonder:

Is it necessary to wire the switch in the way illflem suggest (Bill I'm not saying you are wrong, just looking for more comments)?

This brings up something I've wondered for a while, do the switches affect the reading of the gauge (pyro, oil temp)? What about using crimp connectors instead of soldering the wires?

 

[illflem]

Ryan,what you need to watch for is just junctions of dissimilar metals,that's exactly what a thermocouple is. Radio Shack has the right switches,they're common,because making your own accidental thermocouple is something to be avoided in all millivolt systems. No big deal whatsoever.

 

[Michael Hughes]

kollmer,
I just got done installing a EGT/Boost gaugle with two sensors. I went to Rat Shack and got a DPDT switch and mounted it next to the gauge on the A pillar. illflem is right on how to wire the switch. I would also advise you to use solder type connection for the switch. Polarity is the most important thing when doing this. Hope this helps!!

------------------
1999 2500 ST LB 4X4 Metallic Red, 5-speed, 3. 54 gears, LSD, camper and tow package

 

[kollmer]

Thanks for all the input! Does'nt sound as bad as I thought. Now is it worth it to put a pryo pre and post. There was a recent thread and every other opinion said something else. Pre is better... post is better. Is having both the solution? #ad


------------------
2001 2500 ETH/DEE all Black short bed, Rhino lined, Mag-Hytec rear cover, Amsoil throughout including Amsoil Dual Remote Filter System using RemoteBracket mounting system. Everthing else but leather.
http://sites.netscape.net/remotebracket/homepage

 

[illflem]

Ryan,there is special thermocouple wire,what's so special about it I haven't a clue, maybe someone else knows. The wire is readily available and not expensive,but probably not at Radio Shack. What seems more important to me is that all the wire is the same gauge and length. The installation instructions for my pyro said not to cut the wire,to coil up any extra,the wire length is calibrated to the gauge. I personally don't think this is an issue with such a short run,other folks here have said the same thing,but do keep both runs the same length.

 

[Cooker]

illflem,
I read the same thing about the thermocouple wires (do not cut them), but I called the guys at egauges.com to ask them this question. Their response was that they have had customers who wanted to wire a pyro to a pusher motorhome where the wire had to go 30 feet or so and they contacted VDO about the situation. The wire that connects the leads of the probe to the gauge is nothing special. The were informed by VDO to use a quality 16 gauge wire if the wiring of the gauge needed to be altered from their standard lead supplied. However, and I think this is obvious, the leads off the thermocouple itself are special and care must be taken not to cut or damage these.

I hope this clarifies things for anybody else thinking about hooking up two probes to one gauge.

Ryan
Again thanks for the info on the switch.

 

[Cooker]

I like to thank everyone for their reply's. I have two thremocouples sitting on the bench right now waiting for install and I'm glad this topic was brought up.

Another question, if avoiding the use of dissimilar metals is the most important issue, is the use of copper wire ok for the leads to the thermocouple? Sorry if this question seems so simple, but I'm just wondering.

Thanks again,
Ryan

 

[Rambling]

-Long as usual. #ad
-

As has already been stated, a voltage differential is created at the juncture of two dissimilar metals. Each wire is made of a different metal. The type of thermocouple (K, T, J etc) is detemined by the two metals used. The length of a wire in our case, is insignificant because there is very little current. The bigger concern, which has already been mentioned, is any connection that has different materials. A new dissimilar junction will be formed. The amount of error the connection will cause depends on primarily two things 1)what the two metals are and 2)the temperature of the junction during measurement. Thermocouple extension wire is a diffent grade of thermocouple wire. It isn't normally used to take meausurments but will behave as described at a junction.

Something to try:
When you get everything together and before you install, hook up a probe directly to the meter and place the probe tip in hot water. . the hotter the better. Now install the probe to the switch and a short piece of what ever type of wire you going to use from the switch to the guage. Using water at the same temperature as before, measure again. What you will now see is any error caused by the switch junctions and the junctions at the meter if you use something other than the thermocouple wire. You might try a hair dryer on the switch junctions to see if there are any effects from change in cab temperatures.

Just a thought.

[This message has been edited by Rattlin (edited 03-11-2001). ]

 

[Waterpete]

I have done just what you are asking about. I just went to Radio Shack and bought a relay with a socket ans a switch, that I could solder. I addionally bought a second Isspro sender that was variable as to depth. I then mounted my relay behind the air filter in the engine compartment. I wired the relay so that without power, the relay sent the signal from the Pre turbo sender to my gauge. I'm happy with it. I also bought a second sender for my transmission and put it in the pan of my Mag Hytec. The other sender is in the transmission outlet going to the cooler. Both seem to work great. If you need help just call me at 702-524-7440.

Pete

 

[Cooker]

Here is a little more to add to this topic: https://www.turbodieselregister.com/ubb//Forum3/HTML/000806.html

 

[Cooker]

zman,
I am concerned about the same issue. I feel the "standard" connectors are just fine. Maybe I'm wrong, but if I don't convince myself of that I'm always going to wonder.

 

[illflem]

zman, if the connecters you used were the standard crimp-on type they were copper with a very thin tin coating, you will have no problem. The connecters that are very shiny, usually for larger gauge wire and are called high temp or heavy duty are the ones to avoid, they are a nickel alloy. They also don't have the plastic insulation and come from a hardware store at a higher price, they aren't usually to be found in an auto parts store.

 

[Cooker]

illflem,
The "cheapo" crimp on, insulated connectors are copper on the inside? I guess I learn something new every day.

 

[Jones]

Just my 2 cents but I was told that the idea behind not cutting thermocouple leads is that a lot of them use the resistance in the wires to fine-tune the gauge accuracy. Don't know is thats true for all but the ones we use at work all specify "do not cut leads".
Hope this helps, Jones

------------------
Jones
'84 Ramcharger w/CTD, non-gated 12, torqflite, NP205, Dana 60 and 70 w/ 3. 07s. Straight piped 3" to x-member 4" the rest of the way.

 

[zman]

hmmmm. With all this talk about dissimilar metals, I'm wondering about the connectors that I used to attach the pyro probe lead to the back of the guage. I used whatever I had in my garage. Should those have been copper???

Thanks.

Steve

 

[illflem]

Yeah Ryan they are copper. The silver colored coating on the outside is for corrosion, if you look at one that has been screwed down you will see that most times the screw has actually rubbed the coating off.