Radiator fan troubles and the fix

[SCGallo2]

I have been seeing posts and been sent private messages about inoperative radiator fans, so I figured I would share my recent experience and the fix. In preparation for larger injectors and a custom tune back in April, I scanned for DTC codes and was surprised when I saw P0481 Fan 2 (high speed fan) control circuit fault. I cleared it and went for a short drive and the code came back. So I replaced the high speed fan relay, and all was well for about a week, then the relay that I installed burned up. Since the wires to the fan checked good, I assumed the radiator fan motor was on its way out, causing an over current condition, thus burning up relays. So I replaced the radiator fan assembly with an upgraded 2013/14 unit. At this point, all was well. I got the car tuned for larger injectors and life was good… for a couple of months anyway.


My next indication that my fans were not functioning correctly was my temperature gauge soaring towards red during some slow downtown driving. Fortunately I caught it in time, so I shut the car off before it really got hot. Letting it cool for a couple of minutes, I fired it back up with the hood raised to see if the radiator fan was running and it was not. So, I switched the A/C on full cold and blower speed to high which should activate the radiator cooling fan, but it did not turn on. After a long cool down, I limped the car back home and began diagnosing, but the low and high speed fan were now working!? So I now had an intermittent fan problem, with no DTCs.


What I eventually discovered was the high speed fan relay had a loose connection on the 12V 40 amp supply for the fan, causing arcing inside the fuse panel. After cleaning up the contact and replacing the relay again, everything appeared to be working normally. I did some reading in the Ford Powertrain manual and found out that PCM can shut down the cooling fan motor (low and high speed) under certain conditions such as when it senses an over current and MAY NOT set a DTC. Confidence is now high that I fixed my intermittent fan problem. Now for the operational checkout…


I created a configuration file to datalog engine temp and low speed and high speed activation points. I quickly discovered that my low speed fan was coming on at 185 degrees and the high speed fan was activating at 195 degrees. If I had a 170 degree thermostat, all would be kosher, but I have an OEM thermostat that regulates my engine temp at a 195 degree average. So at this point, the high speed fan would activate and never turn off, and that little relay gets really hot with 40 amps surging through it continuously. So with my trusty SCT X4, I set the low speed fan activation temp at 206 degrees and my high speed fan activation temp at 216. Once the low speed fan turns on at 206, it must cool the engine temp down 10 degrees (down to 196) before it will turn off. The radiator fan does not need to run at highway speeds, only when there is no air passing through the radiator. If the low speed fan cannot control the engine temp during low air flow situations, my high speed fan turns on at 216 and it will turn back off when it cools the car down by 6 degrees (down to 210), re-energizing the low speed fan to continue cooling down to 196 before it shuts off. No more cooling fan problems.


Thanks to 54First for posting about HELMINC.COM, where I found the Ford Powertrain manual to assist in my troubleshooting.

 

[SCGallo2]

Cooling fan problems… round two:

My low and high speed radiator fan modes had been working well since my last post above. In the spring, I installed a 180 degree thermostat and adjusted the fan trigger temps to 196*F for low and 202*F for high with my handheld tuner, since my new thermostat now regulated engine coolant temp at 186*F at cruising speed. Two weeks ago, after my car sat in the garage for a few weeks, I took it out for a drive and noticed that my low speed cooling fan was not activating, high speed was coming on at 202*F as programmed. I scanned for DTC codes and there were none. I replaced the low speed fan circuit relay and after more testing, found that the low speed fan was working intermittently, still no DTC codes. So I figured the radiator fan resistor was going bad, even though I had replaced the cooling fan and resistor with a 13/14 fan assembly early last year. Ordered a replacement from Tasca for around $30 shipped, installed it, and no change, still intermittent low speed fan. Scanned once again for fault codes and got P0480, low speed fan circuit fail. Went online to HELMINC.com to access PCM troubleshooting procedures and followed the troubleshooting chart which has you check for operating voltages and open and shorted circuits with a multi-meter. I have a career background in aviation maintenance and electronics, so I have no fear of electrical wiring. I ended up isolating a 40 ohm resistance load (should be less than 5 ohms) on the PCM low speed fan relay “command ON” wire: PCM Engine connector pin 7 to low speed cooling fan relay pin 2 (#86 on the relay). I opened up the fuse box in the engine bay and did not find any issues with the wires or connections. So I cleaned the terminals inside the fuse panel and reseated the jack screw connectors on the bottom of the fuse panel. I read the wire for continuity again and this time got 0 ohms, which indicates a good connection. Bottom line: bad electrical connection in the fuse box, and I had done no recent work in this area which would have induced this failure. Took the car for a couple of long test drives in 90 degree heat, and everything worked perfectly.

Here are the parts and part numbers for the components I replaced:



The fuse box can be disassembled by disconnecting the + battery cable wire and loosening the four jackscrews in the center of the fuse box. You DO NOT have to remove the relays or fuses during this procedure; they can remain in place in the upper assembly:

 

[Tob]

Superb writeup. Clear, concise, and to the point. Thumbs up on the troubleshooting.

 

[RedVenom48]

Excellent writeup! Will be performing cooling mods to my '11 soon and installing a dual fan HE unit. Condition of contacts and connections will be noted.

 

[SCGallo2]

Thanks guys. Intermittent problems can be difficult to diagnose, so hopefully this thread will prevent someone from experiencing the frustration I did if they encounter a similar failure. The cooling fan relay and resistor most certainly can cause this failure, but if replacing those doesn't fix it, you have to look elsewhere.

 

[JayVee]

I am having this exact problem as we speak. I just purchase a NEW #dr3z-8l603-a last week and that seem to fix my fan failure. A buddy of mine sent me this link so now I am looking to warranty the fan resistor for a 2nd one and adding the relay #3f2z-14n089-ca to this equation. Thank you so much for you research and write up. Hopefully, this is my issue and nothing beyond this.

 

[JayVee]

Question, does it really matter GT500 and GT models of this issue. I just noticed or paid attention you own a GT500 and this is a GT500 thread but I have a GT experiencing this same issue. In related to that question the part number for the resistor harness starts with a D and my model starts with a B. But appear to be the exact same item by appearance.

 

[SCGallo2]

You should order the resistor for the cooling fan model you have installed on your car. I have a 2013/14 GT500 fan assembly installed on my 08, so the part number above is correct for that fan assembly. Electrically they are likely the same component, but I see a big difference in the fan motor connector on the 2007/08/09 resistor harness when compared to the 2013/14 harness. There are actually three different cooling fan resistor part numbers for GT500s:

2013/14 - DR3Z-8L603-A
2010/11/12 - BR3Z-8L603-A
2007/08/09 - 7R3Z8L603A

Use this link to identify the correct resistor for your car: http://www.tascaparts.com/

 

[JayVee]

You should order the resistor for the cooling fan model you have installed on your car. I have a 2013/14 GT500 fan assembly installed on my 08, so the part number above is correct for that fan assembly. Electrically they likely the same component, but I see a big difference in the fan motor connector on the 2007/08/09 resistor harness when compared to the 2013/14 harness. There are actually three different cooling fan resistor part numbers for GT500s:

2013/14 - DR3Z-8L603-A
2010/11/12 - BR3Z-8L603-A
2007/08/09 - 7R3Z8L603A

Use this link to identify the correct resistor for your car: http://www.tascaparts.com/

as far as the resistor goes, I just replaced it last week and the part # is the BR3Z-8L603-A. Elder Ford has warrantied the part and I placed a order for the relay, now concerned if it it correct for my vehicle since I do have a 12 GT. Elder has already made it clear it can not be refunded or brought back once ordered.

I found this link that may also help anyone else having this issue since the issue itself has been found beyond your troubleshooting resolution. Seem the issue can route from the PCM all the way to the fan motor at any point between including your tips on the fuse box itself. This is from a 2010 GT:

http://mustangforums.com/forum/4-6l...-gt-overheating-any-ideas-details-inside.html

I just purchased this vehicle 3 weeks ago. It over heated on the 2nd week and now again 1 week later after replacing only the fan resistor harness assembly. Just trying to get to the bottom of it since the car is modified but finding related issues with the overheating in non modified cars so that would be a good thing for me to know its not the mods and is consistent with the cooling system itself.

 

[HillbillyHotRod]

Where on Helminc.com did you find the troubleshooting chart? I could not find anything like that when I went there. Do you have to sign up for the online service?

 

[SCGallo2]

Where on Helminc.com did you find the troubleshooting chart? I could not find anything like that when I went there. Do you have to sign up for the online service?

Yes, I signed up for temporary access to the site, something like $10 for 3 days or so. It is worth it over leaving it at the dealership for them to diagnose and "test drive" your car.

 

[SCGallo2]

... I placed a order for the relay, now concerned if it is correct for my vehicle since I do have a 12 GT.

I am willing to bet that your relay is the same part number as the one above from my GT500. It is a standard relay that is also used for the PCM, rear window defroster, power convertible top (in a vert), and low and high speed cooling fan circuits. You could use your rear window defroster relay to troubleshoot your low speed fan problem.

 

[JayVee]

I am willing to bet that your relay is the same part number as the one above from my GT500. It is a standard relay that is also used for the PCM, rear window defroster, power convertible top (in a vert), and low and high speed cooling fan circuits. You could use your rear window defroster relay to troubleshoot your low speed fan problem.

Good shit! I bet your right. Because when I placed the order with your provided part # I asked what description does that provide on their system or yr of Mustang? They answered for the part it does not specify and only describes the relay as a universal relay, just what you said pretty much covering multiple uses throughout the car and systems itself. Ford dist. is closed for the Holiday weekend so therefore my order is placed Mon and receive Tues. I will also update my finding here vs a new thread to share with GT500 & GT owners alike. Thanks SCGallo

 

[JayVee]

(Note: Typing this in a rush) Ok, I believe I have found the source of my problem and found it to be the ONLY part to be the culprit of this PITA overheating issue I have been dealing with for the past 2 weeks. When I removed the Fan Resistor harness I noticed all looked great and the resistor showed no signs of loose tails or burns anywhere. Replaced it any ways. Tomorrow I am suppose to go pick up my warranted Fan Resistor and in addition the Fan relay discussed in this thread. Before doing that, I really went back to what I believe all along to be the issue and I seem to be right!

My car is equipped with a TT kit. As many may know, these kits ALL for the most part relocated the fuse box under the passenger Turbo. In my case, it seems the T clamps threaded hardware rods under the cold side of the turbo of angled in the direction of the fuse box pinning them toward the (light grey) plug harness that plugs into the fan resistor mounted to the shroud. When I say "PINNED" I mean if it was possible, the fuse box would not be able to sneeze! The weight and any force the fuse box is leaning on this plug creating a uneven match prong/connector match from within and has burnt the top left prong and surrounding plastic of the harness plug itself. To test this theory before replacing these parts, I went outside started the car, let it get to temp and dead even with half way on the gauge which is more than normal for the fans to turn on. I then went to the front of the car reached down to this plug, wiggled it, forcing it in more as if making a firm connection...and sure enough, There she blows!~

So, in short it was never the Fan Resistor or anything else for that matter. I will still pick up the Ford replacement I order and covered by Ford in addition the relay. I then will comb through the ground connections as advised here on this thread, in hopes Ford sells that plug alone coming off the harness to the fan resistor. (crossing fingers) Once replaced, FIXED!

Thanks for allowing me to share. If anything else develops I will revisit this thread for assistance or to provide assistance for anyone else troubleshooting as the op has.