johnchabin

iTrader: (2)

I hope Eric doesn't mind me posting this here, but I found it very informative. From the rx7-digest and in its entirety:

Date: Fri, 27 Sep 2002 18:35:13 -0700
From: Eric.L.Wells@health.net
Subject: (rx7) [3] ALERT - check your fan relay wiring harness!!!

Fellow 3rd gen owners/enthusiast -

Today while idling and changing maps after a logging run with my PFC and datalogit software I suddenly noticed my water temp gauge shoot up to high. Oh, crap - I looked at the Commander and my water temps were 115C! I quickly shut down, opened my hood, and began to cycle my motor on and off to circulate the coolant to try to get it to cool down (once the motor was shut off the temps went to 135C). With the hood up I noticed that my fans were not coming on, which explained the high temps. Fortunately I had just come off the freeway and I don't think the temps stayed there for a great length of time, and it was unusually cool for Sacramento at this time of year (around 70F ambient in the morning). I towed the car to Checkpoint, and we made an interesting discovery that I wanted to share with all of you asap, which you should check on your cars asap to prevent potential disaster.

We saw that the fan fuse had blown, which is a 60 amp fuse. That's a pretty powerful short to blow that thing, so we really wanted to figure out what caused it. After jumpering the fuse we were able to activate the fans at 85C (I had set that as the low speed setting via the datalogit), but could not get them to activate at 88C (where I had set the high speed to activate). We pulled the top two fan relays on the front passenger side and found the high speed relay to be toast, and when jumpered we could get the high speed to activate. We then pulled the entire harness off the engine bay and found that the ENTIRE unit had very corroded connectors and had COMPLETELY MELTED/FUSED several other connectors, and had even burnt down to the main loom for about one foot. Apparently what happens is over time the heat causes the female ends of the metal connections to widen and loosen, so that the male end doesn't make solid contact and begins to arc. Eventually it just melts down.

Chris went to three other used 3rd gens and found that ALL THREE HAD THE SAME SIGNS of damage, and that their high speed settings didn't work due to the damage. It was only a matter of time before the same short that I experienced happened to those customer's cars. He also found that the later model replacement main loom eliminates the fan relay pigtail and goes straight to the relays now, so Mazda obviously knew it was a problem and fixed it, but I've not heard of a recall. Hmmmmm.

We're going to eliminate the pigtail and solder/heatshrink the relays directly to the main loom, to simulate the replacement main loom setup. Fortunately I still have enough loom left to use what's there rather than have to replace that, too.

Everyone with a 3rd gen - PLEASE go out to your car this weekend and inspect your fan relay harness for impending failure. I'd hate to see someone experience engine death or an engine fire that would destroy yet another of our fine cars. Hopefully my experience can prevent someone else from having the same issue.

Still waiting for the Apexi 3 bar MAP sensor ..... 400rwhp is just around the corner......


elw

johnchabin

iTrader: (2)

Anyone else seen this issue?

TWIFOSP

Yup I bought mine and shortly after had a temp problem. My friend was like, check the fuse. We popped the hood, pulled the 60a out and the middle of it was brown, not the bright orange copper you normally see.

Problem sovled. I'd take pictures but I'm not sure i have the blown fuse...

I'm sure you all know what a blown fuse looks like anyway....

Trexthe3rd

Don't know why more people just simply bypass the whole mess of wires and relays, just use a stand alone temperature fan control. The logic is beyond me.

mmonaco

just checked mine and it looks fine, thanks thought.
john were is centennial, im in westminister.
Marc

johnchabin

iTrader: (2)

Hi mmonaco-

Centennial is the new city south of arapahoe road and north or county line.

We're talking about having an FD club. Interested?

https://www.rx7club.com/forum/showth...11#post1083211

93RxSeven

TWIFOSP - The importance of the post isn't really the fuse, it's what the fuse signifies - it takes quite a bit to blow a 60 amp fuse and the fact that yours is browning, could possibly mean that the relay is starting to separate, and beginning to arc, etc. Don't just check the fuse, check the relay to make sure it's not loose. Then solder it or something to ensure heat won't expand the connections so they come loose. Once that happens if they ground or arc they start melting and could cause the engine fire. If your relay is going out like noted above, changing the fuse only makes it more possible for the the power to continue arcing and melting out the components. Get to it, man!

Air-Rex

About 2 months ago mine blew the fuse. but it was caused the isulation worn though on the wiring on one of the fan motors.