Pre and post-turbo thermocouple switch??

[CumminsPower98]

Hi all,

I am wondering what type of switch I need for switching between thermocouples for my Pyro guauge (Atuo Meter Ultra-Lite). I have read several places about a "DPDT" switch, what is this? I received one of my thermocouples today and hope the rest of the parts come tomorrow so I can do the install this weekend. I just need to know what sort of switch I need to look for. I think I would like a rocker type switch, possibly lighted. If anyone has a thought on this I would love to hear it. TIA

Mark


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Red 1998 Dodge Ram 2500 4X4 Quad Cab, CTD 12 Valve, Long Bed, 5-speed, 3. 54 gears, Camper/Tow pkg, 33x12. 50x16. 5 BFG A/T's, Rancho RS9000 Shocks, Tuff Country Leveling Kit, Straight Piped, K&N Air Filter, Silencer Ring Hanging in Shop, Yet to be Bombed, 70K+ Miles. My web site: www.mark74.com

 

[JIM S.]

Mark. . your going to want to have a heavy duty switch!. . we'er talking temps up to 1300-1400 deg. !!! so I am thinking of a titanium housing with gold plated carbon fiber for the contacts... . and I would say 4-6 gauge wire too!! the biggest prob I see will be a place to mount the sucker!! might have to make a plexi-glass inclosure and put it in place of the back seat... you need to be able to switch from inside right?... other wise you could put it in the bed!


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1995, 2500, 4x4, 3. 54, auto,130,000 miles, custom fuel plate, boost and EGT gauges, 215 HP injectors, RE-0880, custom 4" from down pipe.

 

[EMDDIESEL]

A "DPDT" Swicth is a "Double Pole, Double Throw" switch. Any Radio Shack will sell them and most likely lighted too. Before you power anything up once you install it, DOUBLE CHECK ALL YOUR WIRING. If you dont follow the wiring instructions regarding what color goes where, you will fry your EGT signal box. Many a time i had thought i wired something right the first time only to find out while double checking i was wrong

 

[illflem]

Most pyros generate voltage, the amount depending on the heat, so both wires are essential, no ground or common, that's why you will need a double pole double throw switch. The wires to the gauge will come off the center two terminals, with the paired t-coupe wires on opposite ends. Make sure the polarity is the same all the way though. Many DPDT switches come with a center off position, you don't want this type for this application, just get an on /on type. Also make sure any lighting comes off separate poles than the t-coupe or gauge wires.

 

[CumminsPower98]

Thanks guys, that is the info I needed. I will check here at Radio Shack, I'm sure they will have something. I will definitely be double-checking my hook up EMDDIESEL, I am the same way. I enjoy building computers (mostly my own) and I do a lot of double checking and am always scared when I fire the thing up the first time after putting it all together or adding a part, can't be too careful when dealing with expensive hardware.

Thanks again,
Mark


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Red 1998 Dodge Ram 2500 4X4 Quad Cab, CTD 12 Valve, Long Bed, 5-speed, 3. 54 gears, Camper/Tow pkg, 33x12. 50x16. 5 BFG A/T's, Rancho RS9000 Shocks, Tuff Country Leveling Kit, Straight Piped, K&N Air Filter, Silencer Ring Hanging in Shop, Yet to be Bombed, 70K+ Miles. My web site: www.mark74.com

 

[JGK]

CumminsPower98,

Seems to me when I installed mine there was a warning not to change the length of the wire (i. e. cut off the extra, just coil it up somewhere). The gauge is sensitive to the capacitance/resistance in the wire and changing the length would screw up the calibration of the gauge. Adding a switch and extra wire may do the same.

Someone correct me if I'm wrong...

illflem?

Jay

 

[EMDDIESEL]

Correct on altering the wire length. But they give you enough wire on the Thermocouple leads to reach your switch location pretty much anywhere in the cab. Then, just be sure and mount the signal box as close as possible to the switch. 10-12" of Wire from the switch to the Box wont hurt your readings. Maybe your gauge would be off by . 0001 degrees. In other words, dont worry.

 

[Cooker]

This was hashed over a little bit here:
https://www.turbodieselregister.com/ubb//Forum3/HTML/003013.html

 

[radixr]

I don't think extra copper wire from the ends of the thermocouple(s) will make any significant difference in your readings. I have at least 5 feet of wire running from the thermocouples, thru the DPDT switch and on to the gauge. My post turbo readings are the same as before I added the pre-turbo thermocouple, switch and wiring.

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1996 Dodge 2500 4X4 SC, SLT,Cummins 12V, 5-spd. , JRE 4" exhaust (my kitty ran away into the woods and the muffler fell off!), TST 280 HP/685 Ft-Lb Uprate Kit, AFC Spring Kit, ATS 3-piece Exhaust Manifold, Chrome Valve Covers, Horton Fan Clutch, Jacobs/Ram Exhaust Brake, MagHytec Differential Cover, Prime-Loc, Rancho RS9000 Shocks, Combo Gauge, K&N Air Filter, Brite-Box, Geno's finger-touch oil pan drain plug, Optima Yellow Tops, no turbo silencer ring, full-time fog lights.

[This message has been edited by radixr (edited 05-11-2001). ]

 

[illflem]

Only thing I can add is that it's best to keep the leads to both T-couples the same. I have heard that extending the leads from a pusher motorhome pyro doesn't effect the readings much, that can be a lot of extra wire. You are probably more likely to lose voltage at any connections, I prefer to solder them, even the crimp type,for that reason.

 

[Ladders]

I have 2 probes and use the Autometer (with the power box). When I talked with Autometer about the setup, the only thing they warned me about was switch resistance. I extended the wires into the cab with CAT5e wire (low resistance and signal certified) and send it back to the box in the eng compartment. The meter is connectd to the box, so only 3 pair were used: 1 pair for pre turbo, 1 pair for post turbo, 1 pair to the power box where one thermo would normally be connected. I dont notice any difference if I connect the thermo direct to the box or use the xtra wire to the switch and back (about 4' worth - so total added = 8'). If the switch (in this case) was a high resistance, then the readings would be LOW for the swiched readings vs the direct connection. My box has power all the time so I can always get temp readings from either probe.

I realize that different setups use different components, so mine is only for the Autometer. If you go with a "direct" probe to meter there will be other considerations to be taken into account.

Yes, I did go to the other threads and re-read them, so my above answer is based upon that. The VDO's may use a direct connection and the dissimular metals would have an effect but with the Autometers there doesnt SEEM to be any effect.

\\BF//