NYsNumba1Man

When I bought my xj the temp gauge never worked. I didn't make a big deal out of it since its winter and never feared it overheating as long as I had coolant and kept the heat on. Today was a bit warmer and I noticed as I drove and stopped my efan would click on for a minute or 2 and click off.
I already replaced the coolant temperature sensor so I could rule that out but I read in a thread that a 99 motor has a different coolant temp system than a 96. Well I have a 99 engine in my 96.
Is there anything I can do besides running an auxiliary temp gauge? this is pretty much the only thing left to fix haha

NYsNumba1Man

Bump

djb383

Since u have a OBD-II XJ, one option would be a ScanGauge and just plug it into the ALDL port under the dash. It'll tell u coolant temp plus a whole lot more.

http://www.scangauge.com/

NYsNumba1Man

Wait, in another thread i read that the temp sensor is in the back of the head? Whats on the t-stat housing then?

treah

The one on the t-stat housing runs the computer the one for the gauge is on the back of motor near the end of the fuel rail. I'll post up a pic after class.

ultimate-xj

One is for the gauge on the dash one is for the computer

djb383

'99 heads don't have a gauge sending unit hole......only '96 and earlier. The factory change was made '97 up. '97 up have only one temp sending unit and it's now called a coolant temp sensor and it's located in the t-stat cover. The ScanGauge receives its signal (coolant temp and other info) from the ECU.

MrSchaeferPants

Not sure about your application as I have a 87. But there's probably two, a sender for the computer, and a sender for the gauge itself. If your gauge doesn't work, first verify the gauge itself in working, and trace it to see if you have two sending units. If you do have two, and replaced the one that sends signals to the computer, then it won't have anything to do with your dash gauge. You'd have to search the forums or web, or get a book with wiring diagrams and trace the path.

Just keep in mind what I'm saying is very general, and may or may not apply to your 99/96 issue, but most vehicles in general work this way, or at least older ones. Newer vehicles with modern computers may all use the same sender with multiple signal wires. I dunno, I usually stick to the late 80s when purchasing vehicles.

EDIT: Yup yup, what those guys said ^ Guess I took to long typing my response.

treah

Oh didn't know they changed that. Scan tool sounds legit. Any way to just splice into the t-stat sensor?

MrSchaeferPants

Of course it could be done. But with the same ammount of work, it could properly be fixed. If it's the same sending unit, and the gauge doesn't work. Then you've already narrowed the potential problems. I'd start with the gauge itself, test it. If its fine, go to the wires. Corroded wire, knick/cut, poor ground, loose connection. That's where the scan tool would be great, if the sender is sending the info to the computer, and the eng temp is proper, then its one of the above issues with the wire/gauge side.

MrSchaeferPants

Oh I think I understand now, splicing in a the wire because of the 99/96 sending unit difference. Yeah, I wouldn't see why not. If the 99 engine has like 4-5 wires coming out, trace it, see where it goes. If it's supposed to goto the gauge as well, find out if it is. Maybe they did splice it and hook it up, and a connection came undone or something similar.

KD3NE

You're 96 has two sensors.

One on the front is for the computer.

One on the back of the head close to the firewall is for the Cluster Gauge.

Look at the one on the back, that's where your problem is.


EDIT: Never mind ... you got a 99 motor in your 96.

I would still look at the back of the block and see if the Temp Sensor connector is on the harness of the 96. If it is not there the previous owner might have spliced/buggered it up somehow.


.

MrSchaeferPants

Ya, cause I'm sure they had to change the engine harness out for the 99, but a wire/connector for the temp gauge could just be flopping around somewhere near the firewall where it would have connected to the 96 engine.

If that's the case, you'd have to trace the proper wire on the 99 engine harness where it plugs into the sender, and see where it goes, physically. Then find the end of that and connect it to the 96 connector. Could be that easy. With previous owners you never know. Could have been on the 'to do' list and they never did it because where the wire routed was a PITA to get to. Maybe at the most, you'd have to cut the ends off of the two and crimp on some male/female spades and be done. Maybe

NYsNumba1Man

I was already looking at scan gauge, but for 160.... i might as well just fix the problem since i wont need it for anything else

Can someone post up a picture of where the coolant temp sensor near the firewall is located? The PO said he swapped the engine but he could have lied. IIRC i had 2 extra plugs that didn't go anywhere coming out of my harness, i figured out one was for an underhood light and the other i never knew. That could be it then....

How can i test my gauge?

djb383

My guess is the '96 gauge wire is still there (unless cut) but '97 up heads are not drilled/taped for the sending unit to screw into so there's no sending unit to attach the gauge wire too. Splicing the dash gauge wire into the coolant temp sensor wire, at the t-stat cover, could interfere with the signal/info being sent to the ECU by the coolant temp sensor. Not sure I would want to risk it. Anybody out there that has done the splice?.....any ill effects?