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Mazda Ed
Mazda Ed, Auto Service Technician
Category: Dodge
Satisfied Customers: 2223
Experience:  ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
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Town and country: 2001 town and country 3.3L cooling fans run

Customer Question

2001 town and country 3.3L cooling fans run all the time as long as the batter is still charged even with the switch off. i replaced the fan relay with a mopar part and the temp sensor same results any help appreciated
Submitted: 1 year ago.
Category: Dodge
Expert:  Mazda Ed replied 1 year ago.
Hi!

I want to be sure I pull up the correct schematics. What is the 8th digit of your vin #?
Customer: replied 1 year ago.

3

Expert:  Mazda Ed replied 1 year ago.
If you remove the Fan relay do the fans stop then?
Customer: replied 1 year ago.

let me double check one moment

Customer: replied 1 year ago.

when the relay is unplugged the fans dont run

Expert:  Mazda Ed replied 1 year ago.

Ok, now I want you to install the relay and remove fuse #27 (40 Amp) from the Intelligent Power Module. That's chrylser's version of a fuse box... it has fuses and relays in it. See if the fan stays off doing that.

Customer: replied 1 year ago.

pulling the fuse shuts them off

Expert:  Mazda Ed replied 1 year ago.
Ok good! So it sounds like the signal wire from the PCM to the relay is grouding out somewhere and keeping the fans on OR the PCM thinks that fans need to be on and is keeping the wire grounded. Next step is to reinstall the fuse and unhook the solid GRAY connector at the PCM and see if the fans go off. There is a solid gray and a gray/black connector. If it isn't easy to tell the difference then unplug them both.

If the fans stay running then the wire is shorted to ground which we can verify with a multimeter. If the fans shut off then either the PCM is shorted internally or it thinks the fans need to be on.

Let me know what happens so we can continue.
Customer: replied 1 year ago.

I unplugged the top connector they look the same, and the fans dont come on. if its the pcm sounds expensive

Customer: replied 1 year ago.

My bad i forgot to put the fuse in i have disconnected both the plugs from the pcm and the fans still run when the ground is attached to the battery

Expert:  Mazda Ed replied 1 year ago.
Do you have a multimeter so we can verify that the control wire is shorted to ground?
Customer: replied 1 year ago.

let me check

Customer: replied 1 year ago.

i have a small one from radio shack but should do you will have to tell me what settings to use etc


 

Expert:  Mazda Ed replied 1 year ago.
What is the model#, maybe I can pull up a picture?

You want the setting for OHMs.
Customer: replied 1 year ago.

22-802

Customer: replied 1 year ago.

Expert:  Mazda Ed replied 1 year ago.
Ok, according to your manual there should be a setting for KOHms. It is right below the cont. setting. Turn the meter to that setting and touch the leads together. Make sure the meter reads 0 or very close to 0.

Let me know that worked and we can continue.
Customer: replied 1 year ago.

yes it reads 0

Expert:  Mazda Ed replied 1 year ago.
Great, now leave the PCM disconnected and the relay disconnected. Attach one test lead to a good ground and then touch the other test lead to the terminal connected to the Dark Blue/Violet wire. It is pin #4 in the connector. Be careful not to deform the terminal by jamming the meter lead in. Let me know what you get for a reading.
Customer: replied 1 year ago.

ok can i use the battery ground as a ground point if so 29.8

Expert:  Mazda Ed replied 1 year ago.
Yep, that is fine. Well the wire is definitely shorted to ground someplace! A couple of choices here:

1) We can continue to narrow down the area where the short is but that will require disconnecting connectors from the IPM (intelligent power module) and taking more readings.

2) We can replace the wire from the PCM to the fan relay.

Which do you prefer?
Customer: replied 1 year ago.

replace the wire seems simplest your thoughts


 

Expert:  Mazda Ed replied 1 year ago.
Ok replace the wire it is!

On the PCM C2 (solid gray) you are looking for pin #73, it will be a Brown/Violet wire. You need to cut this a few inches from the connector and splice into the Dark Blue/Violet wire at the fan relay. Make sure you cut the wire a few inches back from the relay too. You want enough room on the wire in case you need to make a repair in the future.

Either solder the connections and heat shrink tube them OR crimp connect them with a heat shrinkable crimp connection. Don't use the cheapo hard plastic crimp connectors!
Customer: replied 1 year ago.

ok i will work on this and will let you know how it goes. both of the pcm connectors are solid gray so i will look for the brown solid wire what size wire should i use to splice i will have to get supplies for this so it will take a few to get back to you thanks for your help A+

Customer: replied 1 year ago.

do you have a diagram of the pin 73 wire there are a couple that look brown violet on the top connector to the pcm

Expert:  Mazda Ed replied 1 year ago.
You are looking for a Brown/Violet wire!
If you look inside the connector the center will be gray on one and black on the other.
This picture is looking at the inside of the connector.

graphic



Use the same size wire that you are replacing.
Customer: replied 1 year ago.

Got it it may be tomorrow before i get to this when i can get into the garage with heat i willl pick up supplies today thanks again will rate you when finished

Expert:  Mazda Ed replied 1 year ago.
No problem! You can always get more info about this problem after you rate me too. Just respond back to this thread. If you need any help with future questions feel free to request me.
Mazda Ed, Auto Service Technician
Category: Dodge
Satisfied Customers: 2223
Experience: ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
Mazda Ed and 12 other Dodge Specialists are ready to help you
Customer: replied 1 year ago.

i cut these two wires and touched them together prior to finalizing the splice and the fans came on while they were touching with the switch off and the engine cold

Expert:  Mazda Ed replied 1 year ago.
That doesn't make any sense. When you ohm checked the wire you had the PCM and the relay disconnected right?
Customer: replied 1 year ago.

yes they were could the issue be in the pcm block

Expert:  Mazda Ed replied 1 year ago.
With the wires cut and not attached, measure the resistance from the pcm connector to ground and then the relay terminal to ground. You should not get a reading on either wire.

Also, stupid question but you are connecting the 2 wires together and leaving the old section of wire out of the circuit right?
Customer: replied 1 year ago.

yes on the old section of wire is out of the circuit pcm block ok i have to get the meter be a few minutes

Expert:  Mazda Ed replied 1 year ago.
Ok
Customer: replied 1 year ago.

zero reading on both then i plugged in the pcm and got a reading of 1.9 on the wire coming off of it, im in MN and it was so damn cold yesterday i cant say whether the pcm was plugged or unplugged but i was pretty sure i unplugged them

Expert:  Mazda Ed replied 1 year ago.
Ok, well this stinks!

The problem is either in the PCM then or it is being commanded on because of an overtemp condition OR it thinks AC pressure is too high. Can you unplug the the A/C pressure sensor and see if there is still a reading on the PCM side?
Customer: replied 1 year ago.

yes give me an idea of where it is, my fiancee is getting rid of the van in 3 to four months so we can do without ac if thats it,

Expert:  Mazda Ed replied 1 year ago.
I don't have a picture, but it says it is located on a fitting on the A/C liquid line between the filter/drier and the expansion valve in the passenger rear of the engine compartment. It has 3 wires - Dark Blue/Dark Green, Pink/Yellow, Light Blue/Brown.

If unplugging it doesn't change anything let me know and we can check the signal wire (Light Blue/ Brown) for a short.
Customer: replied 1 year ago.

ok unplugged ac sensor connected the fan relay wire to the pcm block and the fans started running, bout ready to put a manual switch in the fan relay line. off when its parked on when its driven rudimentary but this van is cursed

Expert:  Mazda Ed replied 1 year ago.
If you had a scantool we could read the data stream and see if the computer is sensing an overheat or overpressure concern.

Check voltage on the Light Blue/Brown wire. It should not have a reading with the pressure sensor disconnected.
Expert:  Mazda Ed replied 1 year ago.

In my manual it doesn't say the computer needs to be programmed if replaced.

Here are some cheap used computers (I've dealt with McCarty before, they have good parts.)

McCarty Auto Parts USA-GA(Hazlehurst)(NNN) NNN-NNNN/(NNN) NNN-NNNN$50.00


Grassy Auto Parts USA-KY(West-Liberty) 1-800-354-7402 $45.00

 

 

They will ask if you have flex fuel and you do because of the vin 3 that you told me in the beginning.

Customer: replied 1 year ago.

ok im with you i think the computer is the problem

Expert:  Mazda Ed replied 1 year ago.

Well, those used ones are cheap enough I think!

 

Did you check for voltage on the pressure sensor wire I mentioned above?

Customer: replied 1 year ago.
Voltage as 0 it won't start tonight I think the PCM iOS crashed
Expert:  Mazda Ed replied 1 year ago.
Maybe this thing is cursed?!? Are you sure you have the PCM connected?
Customer: replied 1 year ago.
Yep disconnected and reconnected several times the radiator fans run got a p1684 and p1491 code
Expert:  Mazda Ed replied 1 year ago.
Those codes are normal. The P1684 is from resetting the battery and the P1491 code is for the fan relay circuit.
Customer: replied 1 year ago.
Bought a different car today the van is being donated
Expert:  Mazda Ed replied 1 year ago.

Oh ok!

 

I hope you don't have any problems with the new vehicle. But if you do, feel free to look me up.

Customer: replied 1 year ago.
Thanks Ed
Expert:  Mazda Ed replied 1 year ago.
You're welcome!

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