Anyone own a Caravan that can help me out?

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Fingers

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My ambient air sensor got disappeared when my front bumper hit a rock on a gravel road. This isn't the sensor that reports to the computer for air-fuel, but rather just runs the outside air temp indicator inside the vehicle. I don't have the indicator in mine.

The problem is that it still brings up a check engine light so it masks any real problems. I don't want to spend $60 just to make an irrelevant sensor work. My plans is to simply add a resistor or thermistor to mimic a reasonable outdoor temp.

What I need is someone who knows how to use an ohmmeter to measure the resistance of the device. It's located under the front bumper of the 2005 Grand Caravans, so I would think it's somewhere nearby for other years and models.

So if you're a gearhead beer swiller willing to help out a fellow brewer, you have my gratitude. :mug:
 

McKBrew

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Maybe this link will help, maybe not. I couldn't find a good write-up on the ambient temperature sensor, but from what I pieced together it plays a more important role than just sending a signal to an in vehicle unit. I gather that it effects engine performance etc... but again, it's just bits and pieces scattered throughout the internet. The problem I see with your method is you mentioned the sensor is completely gone, so without technical documentation, I think it would be difficulty to figure out what resistance you needed to select the proper resistor to simulate a temperature.
(Maybe I'm reading you wrong).


Can you buy the part cheaper than $60 online?
http://dodgeforum.com/forum/showthread.php?t=43162
 
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Fingers

Fingers

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Maybe this link will help, maybe not. I couldn't find a good write-up on the ambient temperature sensor, but from what I pieced together it plays a more important role than just sending a signal to an in vehicle unit. I gather that it effects engine performance etc... but again, it's just bits and pieces scattered throughout the internet.
The vehicle has two air sensors. There is one located under the battery in the engine compartment that tells the computer what the incoming air temperature is. The computer uses this information to tailor engine performance.

The other sensor is in the bumper and it sends a signal to the overhead console inside the vehicle. Placement is outside the engine compartment because it's a better measurement of the outdoors whereas the engine needs a more accurate measurement of what's actually going into the intake manifold.

Thermistors are really cheap so if I spend $5 for a bag of them, I'm not out that much.(I could use some for building brew related equipment) I suppose I could just put a potentiometer on the cable and dial in a resistance experimentally, but I thought I'd ask anyway. I'm just being lazy. :p
 

bsay

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You should be able to use a multimeter to measure the resistance of the sensor (or the one under the battery) and then buy a resistor of that ohm level to install in place of the bumper sensor. Otherwise, just buy a cheap resistor multi-pack at radio shack (or equivalent) and try resistors until one works.
 
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Fingers

Fingers

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You should be able to use a multimeter to measure the resistance of the sensor
Um, yeah. That was the whole point of the post. The sensor is gone so I need someone else to measure theirs.

(or the one under the battery) and then buy a resistor of that ohm level to install in place of the bumper sensor.
Perhaps I wasn't clear on why I wanted someone to measure theirs. I want to buy a thermistor or resistor to match. I'm not so sure that the sensor under the battery would be the same.
 

Flyin' Lion

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I could, but not until tomorrow--as I'm at work until the morning. I'll check back tomorrow to see if anyone has solved this for you by then.
 

Flyin' Lion

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The sensor is 7.5 Kilo ohms and my daughter is .775 mega ohms, plus I finally got to use my Fluke 73 that I bought off of Ebay.
 
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Fingers

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Thanks so much, Lion. Now if only I handed gotten shanghai'd into fixing someone else's computer I'd be able to give that a try on my car.

So, Chester, VA. I'm guessing your ambient temp is pretty hot there, right?
 

Flyin' Lion

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Thanks so much, Lion. Now if only I handed gotten shanghai'd into fixing someone else's computer I'd be able to give that a try on my car.

So, Chester, VA. I'm guessing your ambient temp is pretty hot there, right?
Ninety degrees today, but its supposed to be in the eighties this weekend (I get to take the brood to Jersey so Grandpa can see the newest addition :().
 
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Fingers

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I thought so. I think what we're looking at here is a 10k @ 25ºC thermistor. That's about 77º degrees fahrenheit. Since thermistors have a negative temperature coefficient, 7.5k at 90º sounds about right. According to eBay and Google, I have to buy 40 of them from China.

I think I'll try jamming a 10k resistor in the connector tomorrow and see what happens. If my check engine light clears, I'll throw ten bucks to Beijing.

I'll let you know what happens.
 

mr_goodwrench

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I know this isn't really much help or have anything to do with your situation, but I just had to share this:

 

Flyin' Lion

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I thought so. I think what we're looking at here is a 10k @ 25ºC thermistor. That's about 77º degrees fahrenheit. Since thermistors have a negative temperature coefficient, 7.5k at 90º sounds about right. According to eBay and Google, I have to buy 40 of them from China.

I think I'll try jamming a 10k resistor in the connector tomorrow and see what happens. If my check engine light clears, I'll throw ten bucks to Beijing.

I'll let you know what happens.
The link that McKBrew posted had a conversation about this probe and the guy replaced his for $7. Would that just be easier?
 
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Fingers

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The link that McKBrew posted had a conversation about this probe and the guy replaced his for $7. Would that just be easier?
Heh. I'd already Googled up that conversation a long time ago when the dealer quoted me $60. I went to Autozone to see what their pricing was like, but they don't seem to offer it. If the guy in the conversation got one for $6 from his dealer, it's probably a different kind of dealer than what I talked to. It was when I couldn't find a $6 sensor that I decided to just buy the thermistors. Even they are $10 but I get 40 of them. Then again, I probably have a 10k fixed resistor in my garage stock.
 
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Fingers

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So I put the 10k resistor in the connector and my check engine light cleared. I'll have to see if there are any performance issues as the outside temperatures change, but for now everything is golden.
 

Flyin' Lion

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I'm glad it worked out for you, and glad I was finally able to help SOMEBODY on these boards.:D
 
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