Hey all. I have a question about my OHC temp probe. I initially installed it just in front of the battery, but found the readings to be off. I then moved it in front of the radiator, immediately behind the front grill assembly (so it is ~4 - 6" in front of the radiator, there's a hole in the central support and the sensor fits behind the central post of the front grill nicely). Temperature seemed somewhat OK for the first day. Now it's reading all over the place. I get 24F in 60F weather, 106F in 50F weather, 90F in 60F weather, there is NO pattern to it.

Is this a bad temperature probe? Could this be caused by the 10 gauge wire I've used to run to the probe? I've triple checked my connections and the sensor wires are in fact running to the sensor. Ideas anyone? I'd rather get someone's opinion before going out and splurging for a new temp probe (or risking getting another bad one from the JY).

 

Did you hook up the speed sensor wire? I think that it has an effect on the tempature. If it's not you should hook it up and see what happens. If not I'm sure someone on here has an extra sensor. I have one somewhere and I'd send it for free if I could find it.

 

The speed sensor plays a role in updating.

What type of connections did you make? If they are not water tight they may have corroded and are causing you problems. I suggest buying some 18 awg wire and making a new run.


I believe Bob has a chart (or knows where to look) relating temp to resistance. That my help you.

 

I don't have a chart, just this info from Mr. Griggs:
My opinion is, if the temperature is floating unpredictably, you're probably looking at a poor connection between the console and the sensor. If it is hanging and not updating as you drive, it could be the speed sensor issue.

 

I found this looking for info on the 99 ford truck cd. Its a lil more vague than what Griggs
found. However it does give a slightly broader temp range.

 

Are the wires on the sensor BL/WH and BL/YW I believe thats what they are. Maybe you have the wrong sensor.

 

Good thought but the EATC sensor would make the overhead console read proportionately low rather than float unpredictably.

 

I am using soldered connections wrapped tightly in electrical tape (didn't have any heat shrink on hand). Yes the VSS wire is hooked up but with a blue wiretap. The sensor that came with the OHC does have the blue/white and blue/yellow wires.

In an initial guess (some time ago) that my wire gauge was off, I measured resistance from the connector at the OHC to one of the terminals going into the temperature sensor on one wire and found it to be 0.1 ohms... I don't think that would have too bad of an effect... maybe I should measure the other run.

I will take a resistance measurement when I get home. One thing I have noticed is that I have had a temperature > 100 degrees these past 3 days. Today it dropped down to 77, but there was a lot of mist hitting the sensor. I have to wonder if the sensor wires are picking up interference from two +12v feed wires bundled in the same run of tubing (they run parallel for ~ 2-3 feet).

-- additional info added after thinking about it --

The temperature always seems to match what it read when the truck was last turned off, no matter how much the ambient temperature outside has changed (eg: 70F - 45F). It will slowly drift either down or up anywhere from 5 to 40 degrees F and then just peg there after a while. I'm faily sure I tapped into the correct VSS wire (gray/black to the module behind the radio.)

 

Get a 20k pot, set it at 10k. Put that in place of the temp sensor. Solder in your vss if you think the tap maybe an issue.

Vary the resistance as your drivng (small changes). If the cluster functions like it should your sensor maybe fubar. If not the OHC maybe junk.

 

Just got in from measuring this thing. Thanks to all who have replied so far.

From the OHC harness connector: 45.1 ohms, reading 21F in 49F weather.
Taking the top half of the sensor out and measuring it's resistance in 49F weather: 225-335 ohms.

Could it be whatever grease is on the pins causing my multimeter to read almost 340 ohms directly across the sensor?

More results in. I used several resistors to test and see what values came back:

@46Kohms: 21F (matches what is above)
@14.7K - 50F
@10K - 63F
@5K - 74F

Also tested a 3K, but my helper forgot to write the number down. I think it was in the 90's.

 

It sounds like your sensor has a short inside.

http://www.rockauto.com/catalog/x,ca...,parttype,7000

20 bux for a new one

 

Ordered the sensor, it arrived today.

Went to install it and noticed one small problem...

Old sensor is female. New sensor is male. Now I'm looking at this male to male connection going

Am I missing something???

 

DOH!!!!

Do you know what year your sensor was? I assume it makes a difference.

Also is the pic of the part the correct one?

Call them up, they have great customer service.

 

silly question, but have ya though about placing the sensor where it is OEM in the explorer? If you don't know it's in front of the driver's side headlight, just below the headlight itself. You should see what appears to be another sensor (not sure if it is or not), but I placed my OHC temp sensor near there figuring that was a good location since it's in the same general area on the explorer. It's raining here right now. I'll try to get pics if I can later.

 

Yeah, can't be sure which year this sensor is from at this point. I did notice from another thread that the probe that was sent is for a different year. Mine looks exactly like the one without the point (the removable proble looks like part that has the wires coming out for this sensor). Bet I could cut the old sensor apart and tap into that socket since they match perfectly.

I've tried 2 locations with this probe. First was directly in front of the battery, then in front of the grill. Not sure where it was on the explorer (bought through eBay... I got ripped off I'm sure but nobody around my area had one). Behind the headlight, huh? I'll try relocating it there before cutting it up and see if it streightens out. Could explain the high readings... although I thought that driving down the road at 40-50mph would prevent engine heat from being a factor 6" out front...

Edit: Wired in new sensor using gator clips, sensor was pegged at 29F (same as it had been reading on the way home a few hours ago). Drove halfway down the driveway and back (~1/2 - 3/4 mile total) and it didn't budge. Didn't exceed 15mph though as sensor was literally held onto vehicle. Unplugged sensor and still saw 29F. Suspect bad VSS connection, will double check tomorrow after work.

 

pics on the way........

my probe location, looking from underneath. Notice 2nd "sensor" (not sure what it is) to the left...



OHC sensor obscurred from view by 2nd "sensor" and showing body mount in upper right of picture.

 

Have you calibrated as well? Not that it should matter with temp since I believe calibrating the OHC is just for the compass. Can't go wrong with 2x the VSS wire though......

follow this link https://www.ranger-forums.com/forum2...ad.php?t=29877

 

Yeah, that's basically within 6" of where I moved mine. It's in one of the holes in that area. Read 8F today (50F weather). Started off at 28F and just fell.

As I noted before, there is some sort of goop on the connectors for the sensor. When testing the sensor with a multimeter, this would always throw the sensor way off (read something like 200Kohm). Is there supposed to be some sort of goop in there?

 

No.

The connector should be water tight and not need any grease.

 

Well, went to a jy and got a new temperature probe from an '01 Ranger. Wired it in... still reading the same extremely low values (-2F to 10F in 50 degree weather)... but they seem to have stabilized now, and it does fluctuate some so I know it's not stuck (both up and down, so VSS is good I guess).

This is getting old fast...

Next step is to remove the OHC, snip the temperature wires right at the harness and wire the sensor right there. That should tell me if my wiring is fubar or if the OHC is fubar. Danced with this thing long enough... time to take drastic action I guess.

 

have you set the OHC to your region on the globe? the OHC has a region setting to accept temps from that region you set....if you do a search for it on the forums, there is a write up on how to do it i belive, but i know it has been discussed before...

 

????

I thought the region settings were to account for Magnetic Variation. In other words related to the compass.

 

oooo sounds good! lol....

 

Correct, I believe. And yes, it has been set. I think I'm region 7, I'd have to double-check. My last class is in a few hours here. Then, once I get home my first priority is verifying my new valve for my potato cannon works, then it's over to the OHC to get to the bottom of this (gonna splice in the temp probe right at the OHC connector).

 

Go to radio shack and buy a 40k ohm pot and wire that in place of the temp probe.

set it at 30k (or buy a 30k pot) And see if you get a 70ish degree reading.

This will verify your OHC works and wiring is ok.