Water temp gauge

[Dammerung]

I have the idiot lights on my Jeep, but I don’t want to pull the lights to put in actual gauges. Is there anyway I can install an aftermarket water temperature gauge to check with real numbers? And would I have to replace any sensors or anything. I don’t know where the idiot light sensors are anyways, so any help would be appreciated.

[eaglescout526]

Well I may not be able to recommend aftermarket gauges to you but I can tell you that the temp sender in your case is on the very back of the head of the engine with a little wire plugged in on top of it. Swapping clusters is very easy though. You just need to find either a 5/6th cluster or a full and swap it in and get an oil pressure sensor and temp sensor.

[Dzimm]

You don't replace individual parts, get a full cluster and it will have all the gauges.  The sensors will need changed but that goes for any gauge you put in.

[omega_rugal]

an aftermarket temp gauge will have its own sender

[Dammerung]

an aftermarket temp gauge will have its own sender

But where would I put it?


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[gogmorgo]

If you can get it into the factory spot in the back of the head that would be best. It's a small hole though so it might be easier to adapt something to fit the sensor hole in the HO thermostat housing, which is where the ECU pulls it's reading. But you want it reading somewhere in the head. No other point will be as accurate, and if you put it in the radiator it won't react to a tstat stuck shut. If you've got permanent flow through the heater you can probably T it in there, but it won't be as accurate as the head, and it would be susceptible to a plugged or leaking heater core. 

[Dammerung]

If you can get it into the factory spot in the back of the head that would be best. It's a small hole though so it might be easier to adapt something to fit the sensor hole in the HO thermostat housing, which is where the ECU pulls it's reading. But you want it reading somewhere in the head. No other point will be as accurate, and if you put it in the radiator it won't react to a tstat stuck shut. If you've got permanent flow through the heater you can probably T it in there, but it won't be as accurate as the head, and it would be susceptible to a plugged or leaking heater core. 

So I should just disconnect my idiot light sensor and put in an aftermarket gauge?

Also, mine’s an 88 Renix, so there’s that it it changes anything.

 

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[Eagle]

If you have an '88, the switch for the idiot light is in the back of the cylinder head, on the driver's side.

 

Later years used the PCM to control the water temp gauge/light, and those years had the sensor located in the thrmostat housing. So you can leave the factory switch to keep the idiot light, then get a new thermostat housing with the outlet for a temp sensor and use that to run your aftermarket gauge.

[Minuit]

In this situation, I would always suggest to use the factory gauge... with the stipulation that you use a MOPAR sender only. Aftermarket temp gauge senders are JUNK and not reliable. In my experience, they tend to read higher than a Mopar sender. Aftermarket oil pressure senders seem a little bit more consistent in my experience. Don't complain about how inaccurate the factory gauges are if you stuck crappy aftermarket senders in. The part number you want for most pre '92 applications is 53005309. On the "top" of the sender, there is a threaded stud that the connector attaches to. It does not have a plastic connector molded into it.

 

Starting in 1992, the temperature sender in the rear of the cylinder head changed from a 1-wire to a 2-wire sensor. In 1996, the separate temperature gauge sender was removed and the gauge now pulls its reading from the ECU based on the sensor in the thermostat housing.

 

If both your gauge and sender are working properly (with a MOPAR SENDER), the gauge's needle should be somewhere on top of the "2" in "210" in most cases. This corresponds to a coolant temperature of roughly 195 to 205 degrees. My '91 runs cooler than my '89 due to a larger radiator and the fact that the auxiliary cooling fan is on any time the A/C is on, which is almost always. Steep hill climbs in overdrive and sitting in traffic on extremely hot days are the only cases where I would consider a gauge reading above "on top of the 2" acceptable, and it should immediately return to where it was once you are over the hill or once you have started moving again.

[cruiser54]

Some clarification.

 

Temp and oil sending units for idiot lights can NEVER be used for ANY gauges.

 

Aftermarket gauges will require changing the sending units to match their gauges.

You can use the same location you remove your old senders from. Be aware you may have to do some adapting there. And then there is the accuracy issue with crappy car parts now.......

 

Is this really worth it to you? There's no real easy way to do this if your skill level isn't up to it. 

 

 

 

[Dammerung]

Some clarification.
 
Temp and oil sending units for idiot lights can NEVER be used for ANY gauges.
 
Aftermarket gauges will require changing the sending units to match their gauges.
You can use the same location you remove your old senders from. Be aware you may have to do some adapting there. And then there is the accuracy issue with crappy car parts now.......
 
Is this really worth it to you? There's no real easy way to do this if your skill level isn't up to it. 
 
 
 

I was doing this because I didn’t want to invest in an expensive gauge cluster, but yesterday I managed to pull a full cluster from a Cherokee. So all I need to do is replace the oil and temp sending units with Cherokee/Mopar ones and it all works? Even the tach?


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[JustEmptyEveryPocket]

4 hours ago, Dammerung said:

I was doing this because I didn’t want to invest in an expensive gauge cluster, but yesterday I managed to pull a full cluster from a Cherokee. So all I need to do is replace the oil and temp sending units with Cherokee/Mopar ones and it all works? Even the tach?

Yup.

 

Its just that easy.

[gogmorgo]

I'd just grab the sending units that came out of the XJ you pulled the cluster out of. 

[Rubikahn]

I just swapped over my warning light cluster to a full cluster this afternoon.

 

I haven’t checked voltage off the battery yet cuz I ran out of daylight. From what I’ve read it should read 13.6-14.2 volts. Does it look like it’s where it’s supposed to be?

 

I swapped out the oil pressure sensor to the sending unit and that seems a little high? Read at idle it should read 20-25 psi.

 

The temp gauge is pegged all the way. I know it’s lying cuz I have a REM unit. There was an aftermarket temp gauge wired up when I bought the truck and that read the same as the REM. No stock wiring was touched. Who ever installed it ran new wires including one through the firewall to a ring terminal that was on the temp sensor. I did not swap the sensor at the back of the block because I assumed since the aftermarket gauge worked it was the right one. I do have the correct one for a full cluster if I need to swap it in. 
 

Ignore the lit up right directional, lol. I have a short on the driver side marker light I’m chasing. Any help would be appreciated! 

[Ωhm]

For a factory gauge, here's the spec for the factory coolant temp sender.

 

[eaglescout526]

Also the temp gauge grounds out upon start up. Does it do that and come back down before going to a high temp?

[Rubikahn]

13 hours ago, eaglescout526 said:

Also the temp gauge grounds out upon start up. Does it do that and come back down before going to a high temp?

This morning on cold start up it did, but now that I’m driving it around it’s not. 

[Rubikahn]

14 hours ago, Ωhm said:

For a factory gauge, here's the spec for the factory coolant temp sender.

 

So, I’m checking Ohm readings to verify the sensor or the gauge is operating properly? Where do I check that? 

[Rubikahn]

Got it squared away. Old temp sensor at the back of the block was for the dummy light. I looked around online and read that the aftermarket temp gauges have their own sender? Anyway swapped in the temp sender and it’s reading pretty much what the REM is. However I think I either have a faulty thermostat or the wrong one. Temps only get to the 160s according to the REM.  From what I understand I should be around 210ish on the 4.0. 

[cruiser54]

Use a Mopar 195* stat. 

[Rubikahn]

2 minutes ago, cruiser54 said:

Use a Mopar 195* stat. 

I did order one from the dealer late last week. I have it in hand but it does not say 195* on it anywhere. If the part number is referenced, will it state that it is a 195* thermostat? I asked the parts guy and he couldn’t tell me. 

[cruiser54]

It will be stamped right on it. 

[Rubikahn]

8 minutes ago, cruiser54 said:

It will be stamped right on it. 

It is stamped. It’s pretty tiny and I need glasses 🤣

[cruiser54]

195F

[Rubikahn]

7 minutes ago, cruiser54 said:

195F

Yeah I saw that once I took a picture and enlarged it on my phone, lol