Dual Temperature Senders?

I may have brought this up in the past, but darned if I can’t find anything on here or the Google inter-webs.

I currently have a separate temperature gage on the dash, which is nice, because I can get a fairly accurate temp reading. However, wouldn’t it be neat if the temp gage in the cluster worked at the same time? Yeah, I thought so too.

So I went through the trouble of connecting everything, and what I end up with is a pulsing gage needle - on both gages. They’ll start to rise for a second, then drop for a second, rinse & repeat.

Is there a way to make this happen, without the dancing needles, and without drilling and tapping a new port on the block? I’ve looked in to the in-line radiator hose senders... eh, I’d rather not go there. Electronically, is there a way, maybe via diode, to get both gages to work off one sender?

Thank you Monday morning enthusiasts!
Aaron

 

The factory speedo cluster has been a thorn in the side of most owners ever since it was first introduced in the Jeep models. There is a lot of information out there about how to best go about getting them to work. One common theme to remember is to never put power to the gauges when they are not installed. If the case is not properly grounded, many times it will smoke the gauges. Many Jeeps have a set of add-on gauges installed because of the difficulties of making the factory gauges work properly. It doesn't help as not only were the original gauges very poor quality, the aftermarket replacements seem to be even worse quality then the originals.

 

I totally understand! I rebuilt the cluster a few years back, and seem to remember spending several aggravating days with cheap Chinese-made parts. I know the cluster is set-up correctly now, in fact everything but the temp is working. It’s just awaiting a sender now.

 

Not two gauges, but on my old CJ5, I'd put a hand choke on it and my ex couldn't quite seem to get the idea on how to use one. Leaving the stock temp gauge alone, I put a second 2-prong temp sender out of a 65 Chevy pickup along with a red and green idiot light in the dash for her above the choke knob. Red, it's hot shut it down to cool and green, it's cold and keep the choke pulled out till the green light goes out. And she still had problems with it.

 

You cannot connect both of them to the same sender. The second gauge changes the impedance the first gauge sees, and vice-versa. Electrically, each gauge "sees" both the sender and the other gauge. This apparently sets up an oscillation, which makes the needle bounce. The gauge is expecting to only see a resistor, not a resistor in parallel with another gauge input.

You would have to use something like transistors to isolate each gauge from the other, and then use the sender resistance to control the gate for each transistor, so the gauges would not see each other.

 

Not to high jack,but in the back of my mind I have been thinking of taking aftermarket gauges with matching senders and installing them into the speedo....anybody tried that yet,I'm on the verge of throwing the cluster out and putting a whole aftermarket in the snow plow/rat jeep.

 

Not contradicting Howard, but you could use a toggle switch and select one gauge or the other. Not quite what you asked for ...

 

This is what I’ve been finding on the interwebs as well. It appears to be the standard operating procedure for boats that have dual cockpits. When you move from one cockpit (or is it steering house?) to the other, flip the switch.

Sounds like I’ll need to go the in-line adapter route. Just trying to avoid clutter in the engine bay.

 

Since I got a rebuilt engine, I am running 2 oil pressure gauges. One will be the light in the cluster and will have a pressure gauge hung under he dash. Do not want to drill holes in my new dash. Put a tee in the block with two sending units. Could you use a tee to run two sending units

 

A tee will work fine for a pressure gauge, but for temperature I don't thinj you'd get an accurate reading. The senders would be out of the water flow and would be a little cooler because they're separated from the block.

 

Don't know what engine you have, is there another location to put a sending unit. If it is a V6, you might be able to use the block drain outlet.

 

I have two temp sensors, the gauge on the dash with the factory sensor, the other is a aftermarket mounted under the dash with the sensor mounted at the heater connector on the back of the intake. I have a V6.

Not looking for the two to “Match” exactly. Likely the back of the engine is hotter than the sensor next to the radiator. It all about, for me, is the temp running the same as normal.

 

I’m working with the F134. There’s only the one feisable location, and that’s the stock port on the passenger rear side of block. I’ll end up ordering an in-line adapter for the coolant hose (return to radiator hose). I believe it’s 1.5” diameter... and there’s a 40mm adapter available. Close enough.

 

This project has now made it to the very bottom of my to-do list...