Well my Low Speed relay finally gave out yesterday. It was clicking on and off rapdidly for minutes on end. The high speed burnt up about 3 months ago, and has been replaced. So last night I wired in the new 40Amp relay I had, with a new harness. It was late, so to test it I just flipped on my AC. It came on. When I turned the AC off, it turned off. Great , right?

Well as I just pulled into work this morning, I turn the truck off, and my fan is still going, on low speed. I put the manual switch in, and if I flip it, high speed engages. If I flip it back it retruns to low speed.

So, is the LFP setup like most other thermotstatically controlled fans, and will run until the block cools down? That's all I can think of.

As far as I can remember though, when I would shut my truck up thefan would shut off.
I'm going to head outside and disconnect my battery.

Any ideas gang?

Thanks

 

It seems that there have been far too many efan issues lately.
I had to remove mine as no matter what contoller I used I was getting feed back through the hot side wiring that was causing gremlins..I would walk out to the truck in the middle of the night and the radio would be playing, the interior lights would come on intermittently, or the head or parking lights would turn themselves on. On numerous occasions the fans would turn themselves on while the truck was off and parked..These issues appeared after about 6 months of the fans operating properly....

 

LFP fans are notorious for burning up. Its hands down the cheapest relay/wiring you can buy.

 

Sounds like you connected the low current activation feed wire to a constant 12v instead of switched 12v. That'll keep the low speed relay able to stay energized until the block cools down.


Bird

 

So does that mean it would turn off after a while or not? I drove 25 mins to work, and it's 65 degrees out. I twas still running 10 minutes after I shut her off.
Edit: That can;t be right. I've had this thing in for over a year and it always shuts off. Crap, I'll drive home during lunch and grab the diagram I made when I swapped the relay harness.

Grr...

 

Bird, is this the thin blue wire in the LFP relay pack? I have to get this fixed ASAP.
Thanks!

 

The one that I was thinking about is the red wire that runs to the fuse/relay panel and plugs into the switched power prong - if you have it plugged into an 'always on' power source, the temp sensor will control the fan whether the key is on or off and will allow the fan to run on low speed until the engine temp goes below the shut off point of the sensor (unless the sensor is screwed up). The low speed relay has that 12v going to one side of the energizing coil, and the ground is applied either through the temp sensor or the AC relay - if either one of those is shorted straight to ground, the low speed relay will always be energized as long as 12v is applied through the red wire from the fuse panel.

Bird

ps. there's always the possibility that the low speed relay could be FUBAR'd

 

Well the Low speed is a brand new Bosch unit. The grounding is something I will check. The temp sensor wire is pretty short and is very close to the exhaust manifold. I know it melted the loom a while ago.

So on the LFP setup, the Red wire goes to the "bottom" of the terminal on the passenger side firewall?

I'll check for grounding. It was wet out this morning too.

THANK YOU for the help so far. I'm leaving work early to fix it (or try)

 

You have a large diameter red wire that goes to the 'bottom' of the terminal as you described and a small diameter red wire that runs across to the fuse box - the small one is plugged into the 'key-on' terminal in the fuse box.

 

Bird, thanks for sticking with me. I left work early and started checking everything. I checked the thermostat lead to make sure it wasn't grounding against the block (it's way too short IMO), and it was ok. Pulled both relays out and looked for issues. Checked all the wires as well. I was stumped. On a whim I replaced the brand new Bosch 40A low speed relay with a replacement Tyco one and I'm back up and running like a champ. What are the odds huh?

Anyways, off to the track I go! Woohoo!

Thanks for all the help guys!