Temperature Gauge issue

[JediKnight2]

Just got a 99 Explorer XLS and the temperature gauge doesn't work. Facing the engine I pulled the plug on the left, one wire plug. I grounded it and my gauge pegged at HIGH. That means the gauge itself is good...correct? Figured the sender was bad. I replaced it and it still reads cold even after letting it run. In addition, and this might mean nothing, when I start the vehicle the temperature gauge actually moves down a little. When I turn it off it moves up a little. Better explanation is if you look at the gauge there is a wide tick mark beside C. when running it bounces to the lower part of the tick mark. When I turn it off it bounces to the upper part of the tick mark. I can get a video if that makes any difference.

Also, does it need to be in a specific distance...Its a tight fit in there with a wrench and there is plenty of thread showing...

 

[dustinjorge]

How long did you let it run? I know on my 95 ( which has an additional temp gauge ) the factory gauge low end is 150 or so, so it won't even register until then.

 

[JediKnight2]

not very long, but the truck engine was still warm. Took the connector off again and tightened it up about a quarter of a turn...then the CEL came on...LOL not sure what that was about, wasn't doing anything that should have done that. I cleared it by disconnecting the battery cable...should have had it read as now I am curious.

BTW the part I purchased is WT724 http://shop.advanceautoparts.com/we...d to drive it much with no temperature gauge.

 

[dustinjorge]

Did you by chance use Teflon tape on the fitting? That can prevent the sensor from grounding. The gauge temp sensor shouldn't cause a cel afaik, but you should definitely read the code next time it pops up.

 

[JediKnight2]

It had its own sealant on it, you can see it in the photo

 

[dustinjorge]

The sender for the gauge doesn't have a connector like that on mine... that looks to me like the sender for the pcm, which is on the right side.

 

[dustinjorge]

It should look like this... just an example, get one for your rig..

http://m.advanceautoparts.com/mt/shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_temperature-sending-unit-wells-vehicle-electronics_10305718-p?searchTerm=+temperature+sender

 

[JediKnight2]

Hmmm...looked at Autozone and their part had bare threads so I swapped it out and it moves...just need to make sure its where its supposed to be. I let the truck warm up for maybe 10-15 minutes and it had moved to where it is in the photo. Since I drive a Jimmy I have no clue where the needle should be normally....can anyone help me with that...

 

[dustinjorge]

my needle slightly less than halfway at 197 when the thermostat opens... just make sure you get the right sender... if you got the pcm sender by mistake you will not have movement on the gauge except the slight bounce on initial power. The pcm sender has a 2 wire plug and is on the right side of your thermostat, the gauge sender has one stud and is on the left. Both are variable resistors. The second wire on the pcm sender is ground back to the pcm so it can tell if circuit fails and trigger cel. The gauge sender is similar, but it just grounds to the block. They are specific, and can't be interchanged with each other.

 

[JediKnight2]

99's must be slightly different. The one I changed does have two spade connectors inside the connector harness. The only reason I am sure its the right connector is if I ground it my temp gauge spikes to H. Also, the Autozone part said sends signal to temp gauge. I'm tempted to take it back out and heat it up with a lighter to see if the temp goes up...if it does it might be the thermostat...

 

[dustinjorge]

I have a 4l ohv...

You can test those senders with an ohm meter... there's a chart in the how to on this board that shows what the resistance should be at certain temps.

A stuck open thermostat would cause the truck not to heat up quickly, it would be very noticeable after it does warm up as the temp gauge would rise at idle, then go back down a bit when rpm goes up.

If you do change the thermostat, do yourself a favor and buy a motorcraft, not Napa, AutoZone, etc... the ball bearing air bleed off in the motorcraft part will save you trouble down the road.

 

[dustinjorge]

Here's some reference pics...


Still Cold...

Before Thermostat Opens...

Right when thermostat opens...

After thermostat opens...

 

[JediKnight2]

dustin, do you have a quick link for that...I did a few searches and couldn't seem to find it

 

[dustinjorge]

Here's the chart itself:

 

[JediKnight2]

i will get on this again tomorrow I guess...I set my mm on 20K and put one prong on the prong the wire coincides with and one prong on the base of the sender. Base reading without running was .63, which I assume is 63...after about 5-10 minutes i checked again and it had gone down to .36 or 36...touching the heater hose leaving the water pump it had to be over 86...of course without a reader so i can see what the computer says..its going to be hard to do anything I guess.

 

[JediKnight2]

So...I went out and unplugged my temperature sender and plugged in the one I was taking back to Advance. I grounded the plug on the alternator bracket and hit the tip of the sender with my little butane torch....gauge reacted and rose. SO...the gauge and sender work according to that. JUST IN CASE I took out the sender that was in the vehicle and tested it the same way, same thing happened, temp gauge needle rose.

SO...now I'm lost. The only other thing I could do is boil some water and use that to see where it goes, that would make it at least controlled and I know it should be past the half way mark doing that.

HOWEVER, I am leaning towards this NOT being the gauge or sender...again..I'm at a loss here.

 

[koda2000]

i recently had the same problem on a 2000 Mountaineer V8. the gauge wouldn't move off cold when driving. if it idled for 15 mins it would barely move off cold. eventually it through a code (P0125) which said "coolant temp insufficient for closed loop operation". i had grounded the wire and the gauge registered full HIGH, so i know it was good. the strange thing was i was getting good heat. turned out to be a bad thermostat. replaced it and then the gauge started working normally (needle around the center). the fuel mileage also improved significantly. the gauge isn't really a gauge, it's more like an idiot light with a needle. when the coolant temp is w/in the proper range, the needle will be in the center of its sweep.