Dave_1972

So I recently replaced the gauge cluster with idiot lights in my 1996 XJ with a gauge cluster that has actual gauges (from a 1993 per the seller).

I replaced my Oil Pressure sending unit and my coolant temperature sending unit. (part number: TU236 from AutoBone)

Upon starting the 4.0L - the temp gauge takes about 3-5 minutes to come up into the RED (270-280 I think) way hotter than I think it actually is.

When I went to replace that sending unit I found that it had been disconnected by the PO - and I don't smell the sort of smell I normally associate with an overheating engine. Plus I think the gauge is going up too fast for that to be accurate.

I picked up a Klein IR thermometer and the hottest reading I see is 188 - most of them are in the mid-170's. (guessing I have a 160 Thermostat in the engine?). Holding it on the exposed brass part of the sending unit it was consistent at 175-177.

Has anyone seen something like this before? One friend advised me that something like this can happen if the wire to the sending unit has deteriorated due to prolonged expose to high temp - that it is giving more resistance than it should and resistance is what the gauge is reading.

Does that sound right to you folks? I hate to hack into a factory harness if I can avoid it.

ponderous

I had a similar problem with my '96,when I swapped in gauge cluster from a '94. Tried changing the temp sending unit & the temp switch. New thermostat,flushed system,etc. With IR thermo my hottest reading at the thermo housing was 202,while gauge was buried. I ended up installing an aftermarket mechanical gauge,and to date have never read above 200,even in traffic this summer. I mounted mine in the dash above the cig lighter. Had to drill about a 2" hole (in a blank panel),and you have to careful of the defrost duct work behind that spot. I found out the hard way, but I like the location cause its easy to see. Had to repair duct,but its all good now.

Radi

If you disconnect the temp sender, what does the gauge do?

Dave_1972

With the engine up to temperature (and the gauge well into the red) - I disconnected the sending unit and the gauge dropped back down to 0.

Radi

Well that would clear the gauge and wiring, there isn't a partial short holding the gauge above zero. That leaves the sending unit.
There is a procedure to test the system by substituting a fixed resistor in place of the sender, should make the gauge read a certain temperature. I forget the resistor value, a search might turn it up.

curtisberens

So my temperature sending unit in my 96 cherokee was broken in half but still worked, it would usually read around 150-180 during normal operations. Now after I put a new sending unit in, mine reads around 210-230 during normal operation when it's only 30-40 degrees out, and (I have dual electric fan setup) I never had to turn a fan on on my short drive to school, now I have to have both on or it gets up to 260. Any ideas on what is the problem here.

Radi

Check the temp with an IR thermometer, that'll tell you if you have a real overheat problem or just a gauge problem.
210 or so is normal. 230 should cause the aux. electric fan to kick in with a stock fan setup. Above that is where I get worried. See what you have with a thermometer.
It seems the quality of these aftermarket senders/sensors gets worse every year, but you have to rule out an actual problem first.

Dave_1972

Anyone know what part number this should be? Or if it should be a single or two post connector?

I used the "O'Reallys?" sender part # WT430 as it fit my stock connector (single post) and the choice between it and the other sender indicated the other sender was with a light.

Should it be a sender more similar to # WT3027 with two posts? Meaning I need to change my connector.

Having trouble figuring out which sender it should be looking at AutoBone, O'Reallys?, or NAPA. They aren't doing a good job of specifying which one goes with a gauge.

Dave_1972

So I tried another new sending unit and it also is inaccurate. Even worse than the first one. Everything I am reading on the Internet leads me to believe these sending units are notoriously inaccurate. Rather than continuing to throw money at O'Really's until I find a good one - I am thinking of adding an aftermarket Gauge and sending unit. I'd like to find one with a sending unit that will fit in the stock sending unit location - anyone got a recommendation on one they have used that fits without any modifications? At the sending unit I mean - I'm not that worried about installing the gauge - I can manage that.

Dave_1972

Actually I realized right after my last post that all I really need to know is what NPT size the rear coolant temp sending unit is and get a gauge with a similar size sending unit. I'll measure it this afternoon.

Unless anyone can think of another gotcha.

Fsher21

I had an issue similar to this on my old '96. Here is an option you may want to try, instead of trying to get something that fits into the stock temp sender location at the back of the block. I was unable to find something aftermarket would fit into that stock location. I ended up buying a few different sending units from Advanced until I got one that I didn't break while installing and that measured close enough to the real temp.

You can buy an aftermarket temp gauge and sender, and install it in the heater hose, as close to the thermostat as you can get it to fit. You just need to make/buy a "T" connector to be fitted into the hose. I will look around and see if I have the information that I am talking about, saved somewhere.