www.neons.org

Home of the Neon Enthusiast
It is currently Tue Jul 29, 2014 1:38 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 18 posts ] 
Author Message
 Post subject: Radiator Fan will not kick on when hot
PostPosted: Sun Jun 28, 2009 11:54 pm 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
Okay so randomly my car starts to overheat and I notice the radiator fan does not kick on when the car gets 1/3 of the way hot on the instrument panel which is about the range when the fans should kick on.

So I've replaced the radiator fan relay which is under the battery box since this neon is a 1997 sohc it differs from the 95-96's found in the power distribution box.

After replacing that it still does not kick on so I replaced the next obvious thing, the temp sensor beside the cam shaft sensor. After testing it then it still does not kick on.

So I tested the fan circuit by jumping pins 3 & 4 on the relay plug and wahlah, the fans come on immediately so its obvious there's nothing wrong with the fans or the fan circuit.

I checked for continuity on pin 1 from the relay plug which is black, this is the wire coming from the PCM to the relay and i am getting a ground all the time, when the key is on or off.

So I check wire 2 on the fan relay which is a dark blue and it comes from fuse number 10 in the fuse box beside the door which is a 15 amp fuse that controls a few other things such as fuel pump, torque clutch etc.. and im only getting .003 volts on it.

But i did something crazy and i tested that circuit with a 12v power source and running the negative side of that power source directly down to the multi-meter when i was testing wire 2 which goes to the relay and i get 12 volts.

But I can use the 12v power source and ground the negative side and run the hot side to the non hot side of fuse 10 (which goes out to the devices) and i don't get any power but i can hear the fuel pump kick on.

So with that said I'm completely clueless as to why this issue is happening.

After reading the wiring schematics in my dodge neon book it says that the wire coming from fuse 10 to the relay should be hot when the key is in the running position so that leaves me to assume that the pcm controls the ground side to the relay.

Can anyone check and verify for me with a multimeter that wire 2 (labled on the plug) going to the radiator fan relay is supposed to be hot when the ignition is on?

Fortunately i have to get this issue fixed by Wednesday so if i cant fix it to operate normally I'm going to have to hot wire the hot side of the relay to the ignition so the fans come on all the time when the key is on.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jun 29, 2009 1:34 am 
Offline
New

Joined: Mon Apr 13, 2009 11:32 pm
Posts: 8
I just dealt with similar issues on my '98 R/T circle track car.

Make sure to cover all of the basics. Even with your fans running all time, they may not be able to service a poorly maintained coolant system.

1. Replace your radiator cap if the rubber gasket shows any signs of wear, cracking, or aging. Pressure prevents premature boiling over, which would lead to overheating.

2. Replace your thermostat with a new one. I chose to run stock temp. setting, but paid extra for the failsafe one. It has a weep hole to allow air to bleed out of the system as you fill it. Plus it will pop open if you overheat to allow coolant to flow with restriction until you can stop the engine.

3. Check the condition of your radiator. My radiator looked fine from the front(No A/C condenser in a circle track car), but when I pulled it to take it in to be flow tested, I found the cooling fins were completely shot on the backside. Meaning the fins facing the fans. My cooling fins were so bad they just fell out in 2-3in. chunks at a time.

4. Lastly Hot wiring the fans the "easy way"

Use your FSM to reference the pages below:

14-35 Solid State Fan Relay-PCM Output. This gives a description of how and under what conditions the fan relay is energized. When coolant is at or above 210degF fans=ON. Coolant at or below 199degF fans=OFF. ALSO A/C switch closes at 285psi fans=ON when A/C pressure drops about 40psi fans=OFF.

8W-42-2 Air Conditioning-Heater wiring diagram. Identify wire #18 connected to PCM pin #38 color BR/OR.

8W-80-26 Connector Pin-Outs. Powertrain Control Module. This page shows you connector pin numbering to help locate wire #18 color BR/OR.

Once I found this wire I followed it back about 6 to 8in. from the PCM and cut it. Crimp a wire end on the piece of wire leading back to the PCM. I used the top left PCM mounting stud as my ground. Just tape up the other end and re-wrap the wire harness where you had to cut it open to access wire.

By doing this you are basically telling the computer that the A/C switch is closed fans=ON. The best part is, unlike wiring them to ignition power which runs the fans anytime the key is in the on position, using this method your fans will only run when the engine is running.

Note:Be patient there is like a 3-5 second delay on the fans after you start your car. At first it appears to not work if you test it by just touching the wire to ground and expect the fans to start instantly, they will not. You should be able to "Hot Wire" your fans using this method in less than 15min if you have everything ready when you start.

Remember this was done on my '98 DOHC R/T, but this should be common to all 1gen. Let me know what you eventually find to be the problem. Overheating cars can be quite frustrating. So I hope the above will help somebody.

-Mel


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jun 29, 2009 3:13 pm 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
I dont have the fsm, I have the haynes repair manual.

If someone can just answer these two questions it might help me a little bit.

Is pin 2 of the relay supposed to be hot when the key is on?

does the computer control the hot or the ground to the relay?


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jun 29, 2009 7:55 pm 
Offline
Neon Enthusiast
User avatar

Joined: Wed Mar 12, 2003 3:24 pm
Posts: 330
It seems to me that you are reading the schematics incorrectly.

Power to the radiator fan is HOT at all times even with the key removed. Power to the radiator fan is through Fuse 5 (30A) located in the Power Distribution Center, not the fuse located in the Fuse Box next to the driver's door.

Here are the pins for the solid state relay:

Pin 1 - Black ground
Pin 2 - Dark Green changes to Light Green goes to PCM.
Pin 3 - Light Green goes to radiator fan
Pin 4 - Gray from fuse 5 in PDC, HOT at all times

The PCM activates the fan by grounding Pin 2. The problem you have is located on the control side of the relay. Disconnect Connector 2 of the PCM. Ground Cavity 18 of Connector 2, not the PCM side. The fan should turn on. If not, trace the wiring to the relay.

There's a connector (Light Gray in color) located under the PDC. The Dark Green wire changes to Light Green. Check that connector.

_________________
Our Daily Bread - Practical Tips for a Fulfilling Life

HyperPhysics - The World of Physics

2006 Volvo V70R - 300 hp; 295 ft lb

Image


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Sat Jul 04, 2009 2:13 pm 
Offline
New

Joined: Tue Jun 03, 2008 1:57 pm
Posts: 17
Location: Rockford
Thanks Ishmael

I was having the same problem, after jumping pin 3&4 fan came on.
Then I checked pin 1 to ground it is good. took a look under PDC found the gray connector. The green wire was broke about 3" back reconnected it and fan is working again.

_________________
1995 SOHC 2 door
2002 SOHC
2003 SOHC
1971 408 DEMON


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Sun Jul 05, 2009 4:37 pm 
Offline
Neon Enthusiast
User avatar

Joined: Wed Mar 12, 2003 3:24 pm
Posts: 330
I'm glad I was able to help you. I have seen this problem many times. :good:

I wonder is the original poster solved the problem too.

_________________
Our Daily Bread - Practical Tips for a Fulfilling Life

HyperPhysics - The World of Physics

2006 Volvo V70R - 300 hp; 295 ft lb

Image


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Sun Jul 05, 2009 8:40 pm 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
I'll be checking what you said ishmael tomorrow.

I know pin 1 is grounded all the time. I'm just unsure how pin 2 operates with the PCM. If i cannot figure out the issue im just going to wire it up manually using a standard 12v 30amp relay.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 3:29 pm 
Offline
Neon Enthusiast
User avatar

Joined: Wed Sep 27, 2006 11:46 am
Posts: 471
Location: MARSHVILLE,NC
So the fan relay on a 95-96 is in the fuse/relay box on battery tray not under battery like 97-99 ??

_________________
"R.I.P. MARK RILEY of TURBO TUNE"

BEONNEON jr. viewtopic.php?t=303252
Project FREEZE viewtopic.php?f=51&t=330133


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 3:53 pm 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
Okay so if i ground pin 2 of that goes into the relay and pin 1 is already grounded, how is this supposed to kick the fan on?

Does the relay receive the hot side from the hot side of the fan circuit? I'm trying to find a diagram as to how these relays work.

So let me get this straight, pin 1 and 2 are both grounds on the relay? pin 3 is hot all times due to the 30 amp fuse and pin 4 goes to the hot side of the fan (which the relay shorts 3 and 4 to kick on the fan)

Does anyone have a diagram of the relay?

I also checked the wires below the pdc and they were very oily due to a cam shaft sensor leak i had years ago but i cleaned them off and put new electrical tape around them and no luck. I've yet to pull out the computer and ground cavity 18 of plug 2 going into the pcm. I will try this next.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 4:49 pm 
Offline
Global Moderator
User avatar

Joined: Wed Jan 09, 2002 1:10 pm
Posts: 5831
Location: Weirton, WV
I know recently on mine replaced the wire from the PCM to the relay solved my problem but not sure just so much reading started to confuse me. There is a post by I believe one of the admins can't remember who when I had this issue he posted a link with a test on what to test for etc. I followed what he posted to solve mine completely wish I knew where it was if I get time I will search for it later. If not do a search for rad fans or something like that with me as a poster and you probably will find the post I made.

Lorenzo

_________________
BILLET ALTENATOR OVERDRIVE PULLEYS! 85.00 SHIPPED!
R/T style Vinyl stripes just like the stock ones have $140 non moon roof 130.00 Moon roof + 8 dollars for Shipping in the US


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 7:41 pm 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
okay after completely dismantling my wiring harness going from the bottom of my transmission up to the pdc and into the pcm i've found that the pin 2 wire going into the radiator fan ssr is not cracked or broken in any way.

So this leads me to believe that the computer is not sending the control ground to the relay. I'm going to give it a test and try to ground the wire while the engine is running and see if this fires up the fans.

But so far no luck what so ever...


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 10:36 pm 
Offline
Neon Enthusiast

Joined: Sat Mar 14, 2009 8:11 pm
Posts: 540
Location: Northeast
Check out the archives, post " should the fans be grounded?" or something like that, Heilman I think. My understanding is that the pin that the PCM grounds is fed from the relay, i.e., is from a pull up resistor. Ignition should be in run, but engine does not have to be running, to test this relay, which is actually a solid state switch. Do not supply any voltage to that relay.

I would expect the relay circuit to be a transistor input with 5v on both emitter and base, through appropriate resistors in each leg. With the same v on both, no current flows, transistor is off. But when you ground the base, current can flow in the emitter circuit, turning on the transistor. I have used similar designs often. Grounding is ok, because there are resistors that limit the current. But putting a voltage into it may blow the emitter junction if the designer did not use a lot of protection.

Sounds like you have a wiring or PCM problem. Do the test as Ishmael described.

Jerry


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Mon Jul 06, 2009 11:51 pm 
Offline
Neon Enthusiast
User avatar

Joined: Wed Mar 12, 2003 3:24 pm
Posts: 330
Sir, you are making the problem unnecessarily complicated. Let me use a mechanical relay as an analogy.

Pin 1 is permanently grounded. The grounding point is located behind the driver's side headlight, on the radiator support enclosure. Test for continuity between Cavity 1 of the connector and ground. Pin 1 serves no "functional" purpose. Nevertheless, make sure the ground is good.

Pin 2 is the negative side of the coil. The PCM activates the relay by grounding Pin 2. Check the wiring between Pin 2 and the PCM. A visual inspection is not enough. Use the multimeter to check for continuity between Cavity 2 of the relay connector and Cavity 18 of Connector 2 of the PCM.

Pin 3 is power to the radiator fan, when the relay is activated.

Pin 4 provides power to the coil and to the radiator. Power comes from Fuse 5 in the PDC. Power is HOT at all times, even with the key removed.

When the PCM activates the relay, Pin 3 and Pin 4 are essentially "connected."

There's a connector under the PDC. Check the wiring in that area. Again, a visual inspection is not enough. Use the multimeter.

_________________
Our Daily Bread - Practical Tips for a Fulfilling Life

HyperPhysics - The World of Physics

2006 Volvo V70R - 300 hp; 295 ft lb

Image


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Tue Jul 07, 2009 2:56 am 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
I found a few breaks and shorts in the "fan patch harness" which goes from the fan to the bottom of the frame which has another plug that goes into the wiring harness which in turn goes into the relay.

After fixing this and testing it I'm still having the issue but after fixing that damaged harness I'm now being thrown a 35 error so now it seems like I'm going back to the relay again.

Unfortunately I do not have a multimeter so I'll have to borrow one again tomorrow.

But after grounding pin 13 in the gray connector under the PDC (which goes down to the relay), the fans do not kick on and as you say ishmael, when pin 2 is grounded the relay should energize the mosfet in the SRR.

After dismantling the old srr; I noticed that the relay is fairly simple. The back plate of the relay is used for the ground and pin 1 and 2 are "control" pins used to complete the circuit to energize the relay which in turn connects the circuit from pin 4 to 3.

The relay receives its power from pin 4 and ground from the base plate of the relay. So apparently Chrysler used decided to complete the circuit by grounding the two pins since pin 1 shows continuity between the pin and the ground.

I'm going to test one more thing tonight before i go to bed since its 4:00AM almost. I'm going to try to jump the control pins (pin 1 and 2) at the relay and by doing such the fans should kick on, if not then then I'm clueless.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Tue Jul 07, 2009 9:13 am 
Offline
Neon Mechanic
User avatar

Joined: Thu Jun 15, 2006 1:52 am
Posts: 7717
Location: Phoenix, AZ it's quite hot outside. BUMMER!
BEONNEON wrote:
So the fan relay on a 95-96 is in the fuse/relay box on battery tray not under battery like 97-99 ??


95-96 neons use a conventional relay to run the fans. so the relay is located in the PDC. when they switched to the solid state relay they moved the relay down under the battery. probably to avoid confusion between the two since you cannot use a normal relay in place of the solid state one on 97+ cars.

_________________
F&S Fabrication 2.4L power steering brackets
2008 BMW 335i. Kinda fast I guess.
1999 2.4L coupe now sitting.

jspata17 wrote:
im not that dumb. i cant tell the difference between a inch pound and foot pound torque wrench.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Tue Jul 07, 2009 10:02 am 
Offline
New

Joined: Fri May 20, 2005 6:01 am
Posts: 10
Issue was finally fixed.

Who would have guessed that you could buy a defective part new out of the box? :shock: wow I have such bad luck...

Took my "new" relay back and got an exchange for another "new" relay :smile: and fans kicked right on during normal operating conditions.

Thanks ishmael for your help.


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Sun Oct 31, 2010 10:55 pm 
Offline
New

Joined: Thu Oct 07, 2010 9:33 am
Posts: 15
Location: Black Earth, WI
I have a ’98 DOHC MTX w/AC (AC inop), with an EGR code (32). I do not know if the EGR code has any thing to do with the fans not working but I am trying to give as much information as possible. The EGR seems to pass the mechanical test and the resistance in the control valve matches what I’ve read here, but I have one coming from another member to try to see if I can make the SEL go off. I’ve read about a block off for the EGR but I would like the light to go out, because (and I may be wrong) I want the car to go into closed loop so I can get the best MPG I can get, I don’t think it can get there if the SEL is on. . It also seems like I have to crank a little too long to get the engine to start. Other than that, the car seems to run great. Some how, in trying to diagnose the EGR code, I have discovered that the fans do not run. I have learned from this site that the stock temp gauge can be horribly inaccurate, but it has never indicated an over heating problem. In tracking down the problem, with the great help of the search on this web site and its members knowledge, I have gotten this far;

The fans do not come on with the AC or the defrost. If I ground pin 18 with the PCM unplugged the fans run. So the PCM has the ability to run the fans. Today I pulled out the temp sender, hooked up the ohm meter and went from hot water to ice water, and (again with info from this web site) determined that the thing seems to function normally. Next I plugged the sensor back in, but did not install it, turned on the key and got after it with the propane torch. The gauge in the dash went up to max, and I heard an alarm bell go off, after reassembling every thing I’ve got a code 22, temp gauge out of range, witch makes sense, but the fans still did not turn on!

I put a switch to ground in the wire between pin 18 and the relay so I can turn on the fans, but every time I do that the SEL comes and I get a code 35 (Rad fan control relay circuit), and I’m back to the same old problem.

Could the AC or maybe a switch in the heater/defroster system be the cause? I have also cleaned all the grounds I could find, except the big one by the starter, witch I would think is good as long as the car starts. The wires look ok by the EGR also.

I think I’ve done enough searching to find my answer if it was out there, so I’m going to resort to asking you all for some help. Thanks in advance.

_________________
‘98 Plymouth Neon, 2.0”Y” DHOC, MTX, ATX throttle body


Top
 Profile  
 
 Post subject: Re: Radiator Fan will not kick on when hot
PostPosted: Sat Nov 06, 2010 10:39 am 
Offline
New

Joined: Thu Oct 07, 2010 9:33 am
Posts: 15
Location: Black Earth, WI
:shock: The fans kicked in the other day in the drive way after driving home from work, I was amazed! I still can not get them to come on with the AC or the defroster. Yesterday after coming home from work I let it idle again as I got the mail and nothing, I wiggled the wiring harness and some of the grounds, still nothing.

Any thoughts?

_________________
‘98 Plymouth Neon, 2.0”Y” DHOC, MTX, ATX throttle body


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 18 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot], cameron770, Google Adsense [Bot] and 6 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  


Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Style based on FI Subice by phpBBservice.nl