black bear e harness melted in extreme heat

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bottomline2000

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I had the problem as well. My original PCM didn't control my fans correctly so they were constanly on. My harness eventually melted. I switch to a new 0411 PCM, had BB update my tune and switched to a Nelson harness. relays mounted to the PCM cover and no problems a year later.

My truck also seems to run better with the newer PCM as well. all the harness problems I have seen seem to be from 2000-01 trucks.
 
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candyman74

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I just bought 12 new relays for 2.05 each same ones and im gonna rewire my harness and make the wires longer and beefier. My harness must have been wired with the relays going the wrong way cause theres no way i can mount mine with the relays flat to the computer panel. Also all the power wires were soldered to one small lead i put a larger lead on it now. The place is in california that sells the relays. Its called Accele Electronics Inc 562-809-5090. The relays i had on my harness were beuler 40/60 neg spike
 
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candyman74

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quick update

i replaced all three relays with new ones, put larger wire for power to relays and moved them off to the side. works fine now even in extreme heat, had them running all day saturday and engine ran cool as could be. i still have to extend the wires going to the fans as they are too short for me to properly mount relays to computer cover.
 

sparks

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i have the exact same problem. sockets are each melted, and i agree, the harness - no matter who is building it - is excessively short. im in the process of trying to find an oem harness, or if i have to, i'll build a new harness out of heavier duty relay sockets (found some ceramic ones at a local supplier) as these definitly dont stand up to the heat (i live in florida and its 90+ degrees pretty much every day so my ac is always on, so these are running on high mode all the time). my relay pack is also attached to the pcm cover. im not really impressed with the build quality because of the short harness lentgh and the melting. engine cooling fans are definitly not something to have a failure on because of poor quality components.
 

JennaBear

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The vehicles that are having problems are a very small percentage, but our builder is looking at revisions. Most of the folks who are experiencing these problems, have an insufficient electrical system to power the fans (which is why we now strongly recommend the overdrive pulley, if not a bigger alternator).
 

sparks

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ive got a denali with the 130a alt, and even at idle with fans running full speed the volts dont go below 12.2 (verified with multimeter). in my instance its purely heat, and since the fans blow right at the relay pack and harness because its right at the ecu cover, its got no chance of running cool. i highly recommend having the harnesses made significantly longer so the relay pack can be located out of the flow of hot air. im happy to modify mine and send you measurements as well as pics of where i relocate the pack to once ive extended the harness. pm me if you would like and as soon as i do the repair i'll email all the info to you guys
 

JennaBear

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It actually takes more than 200* to melt the plastic on these. If the plastic is melting, it is a bad ground or voltage issue.

Keep in mind, the stock alternators will have issues running efans, they are not enough for them.

We have let our builder know of current problems with the harnesses and he is looking at fixes.
 

sparks

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hopefully my new relay sockets come before the weekend so i can rebuild and extend. ill document with pics everything when i pull the harness to rebuild it. i did notice today that it almost seems like the relays themselves are coming apart. i do agree that the heat itsself shouldnt be the issue, but ive verified the +12 and ground connections and they are clean and the ground shows no potential difference, so its either a heat thing or possibily the relay and relay socket contacts just arent making good solid contact, or they just cant handle the current. that would make sense because thats where the melting is occurring, the socket and contact area, all of the wire is fine even right out of the sockets, no signs of overheating/melting anywhere.

like i said, i'm going to try and be as helpful as i can be when i pull it apart and inspect, i want to remedy the issue for myself but also for others because this kind of failure can have catastrophic and extremely expensive consequences. i guess im lucky because i know enough to troubleshoot it at roadside and keep things going, but its a nightmare at this point because im having to mess with them 3-4 times a day to keep from overheating...i literally have blisters from the relay packs being so hot lol
 

bottomline2000

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I'm curious as to how often both of your fans are on high. Even in 100+ degree weather my fans only trigger from temps after sitting still for a few minutes. Otherwise they rarely come on.

I replaced a leaky radiator, replaced thermostat, flushed coolant and even replaced my coolant temp sensor and the fans don't work as hard as before. Make sure you not treating a symptom to a bigger problem.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2
 
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