Diodes in cooling fan feeds

larry, that IS the purpose of the fan diodes, they prvent current from backfeeding into the electrical system.........DAVE

...That's correct! Especially if Your running Meriya Fans as, I am!! When You (try to) shut the Engine off, 'they' then become Two Massive DC generators that feed Current to the Ignition System, still providing Spark; The Engine will run on for 15-20 seconds until the 'Generators' come to a complete stop. The Diodes prevent this. OR You can Disconnect the fans and ignition from the Ignition Switch,(The Point at which the Ignition System connects to the Fan Curcuit!) and run them through there own curcuits using relays. I also make sure I shut the Fans off (Manually) Before I 'Kill' the Engine!...

mine must not have the diodes !
as the engine runs on for 5 or so seconds !
I thought it was a turbo timer !!
so if i fit relays to them that will stop it ?

OK, I get it. As long as the radiator temp switches are are calling for fan, very typical situation at engine shut off, as the fans spool down they provide enough juice to keep the ignition energized.

v8capri- I'd try the diode trick first. I've never experienced any run on after shut down

I can't tell you the rating of the stud diodes but I'd guess around 30-40 amp, but besides them all you'll need is two ring terminals and some tape

You'll have to remove the air deflector panel for access (two screws}

The relays are the best way to go because a diode drops 6/10 of a volt.

Mike

I discovered the diode thing as I was removing accessories to pull the radiator to straighten out my valence.

After I got it out I just couldn't make sense of the wiring I found. The wire colors were right, but they seemed to terminate in the wrong spots and some appeared to be missing. Well, I found the missing wires, neatly taped up in the right headlight bucket area and I finally figured out what those two small studs are on the front right side of the reinforcement at the front of the trunk area. Thats where the fan relays are supposed to mount. I wondered why I couldn't find the darn things.

One of Miss P's priors, I'd guess while putting in the diodes, removed the relays and routed the fan wiring directly through the radiator thermostats! The fans never failed me (ignorance is bliss) but now that I know I cannot leave it this way.

I untaped all those other wires and there they all were, the blacks, the brown, the gray. Every wire necesary to match the wiring diagram.

So, I'm going to restore the relays, and follow Mikes Pantera Place cues and diagrams. I'll add one for my auxiliary third fan too. I think that going to the battery for fan power and keeping the load off the ammeter (mine's only a 50A VDO guage) and ignition switch is a good thing.

Now that I know about the voltage drop across the diodes maybe I should try to eliminate them.

How now to control the backfeeding/engine run-on thing? If I should try to shut down while the thermostats have pulled up the relays and are calling for fan, the current path is there for a backfeed and therefore run-on.

I'm afraid if I use a fan master switch like Marlin Jack, someday I'll forget to turn it on!

I have the after market fans also. When frist installed I got the run on also. I in stalled the Rick Mosley (SP) wiring kit with the help of Mike Drew and that stoped that. The kit mounts in the front trunk very neatly and hooks into the your fuse box and routes and reroutes current! It also has a couple extra relays.
I think others make a kit similar to this, and I'm sure someone else can explain what the kit does better then I! I'd look in to a kit like this, it has other benefits also.

Good Luck
Curt

Why not consider this solution?
http://mysite.verizon.net/vzesb3ri/panteraelectronics/id3.html

I just installed the Mariahs last weekend. Now I have about a 5 second or so run on.

#4134 has the 2 original fan relays, should I still have this problem?

I prefer not to go the diode route as Mike explains the current drop.

Any other ideas?

Look Here!
http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562...540075764#8540075764

Thanks. Thats the direction I was headed, excepting Mike's "pantera place" schematic has the 10ga wire getting power directly from the battery. Most posts related to power sourcing call for getting your juice at the ammeter.

Is there a junction of some sort that can be tied into where Georges schematic shows the 10ga wire entering the circuit at the black/pink connection or do I need to attach a rugged ring terminal to my feed and terminate at the ammeter?

The ammeter is taxed, but this is the decision part as on how you want to proceed, if you do not go direct to the battery then you go to the lug at the ammeter for main power and use the old wiring to accuate the relay,
Thats were I used the breaker to feed the fans.
No problems since.

Mark