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Thread: Help - Recreating Fan Wiring Diagram Using Derale Controller & GM Stock System Reply to Thread
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Topic Review (Newest First)
07-13-2012 06:48 PM
LATECH [QUOTE=fcastro;1573374]
LATECH,
My first thought was to use the derale grounding wire to send a ground signal to the wire between the ECM and GM relay. 2 problems, 1 I don't want to damage the ecm, 2 if the GM relay is failing or fails in the future the whole system is dead in the water.

LATECH, do you think you could just quick sketch up the bosch setup you just mentioned? It sounds promising.

The gm ecm would not be damaged, and if the GM relay quits, there are several others under the hood you can swap out to get you home, like say the foglight relay, or DRL relay, or god help us... the AC relay.
The circuit is designed to supply a ground, you would have to do something pretty wrong to hurt it.
The bosch diagram... use the same diagram as in post number 4. Ignore the ecm, run the red(ground) the the relay coil, just like in the picture.
Use the derale controller to trigger a relay coil and not some power hungry fan motor. Let a disposable/dispensable relay do that job.
07-13-2012 12:07 AM
fcastro Thanks so much for all the replies so far guys. I was wondering why I hadn't seen any replies. Apparently the server isn't emailing me notifications even though I am subscribed to the thread.

LATECH,
My first thought was to use the derale grounding wire to send a ground signal to the wire between the ECM and GM relay. 2 problems, 1 I don't want to damage the ecm, 2 if the GM relay is failing or fails in the future the whole system is dead in the water.

LATECH, do you think you could just quick sketch up the bosch setup you just mentioned? It sounds promising.

2x4 Barrels,
Wow yes the original system as it was designed breaks the ground of the Derale system. Do you think you could explain a bit more? That totally sucks if breaking the ground is causing the Derale unit to fail.

cucumber1949,
I have read a few other forums where people also mention derale controllers failing, and there not cheap! the fact that they redesigned the fan controller had me thinking poor quality. My original controller lasted a few years and failed!
07-09-2012 04:47 AM
EOD Guy I use the Dakota Digital controller, so far so good. I got it party due to some of it;s features and ease of install.
07-08-2012 09:27 PM
cucumber1949
Quote:
Originally Posted by LATECH View Post
If you wire the derale ground circuit to the OE relay coil ground as I described, it will prolong the life of the controller.
If you dont have the same setup as the OP just add a relay for the fan circuit, prefferably a 40 amp bosch, and use the derale controller relay to activate the bosch relay COIL, that way the derale control will last as it is only handling a small amount of current to run the Bosch relay which is handling the Load. And the bosch job is dispensable, or at least more so as it is quite a bit cheaper than the derale unit.
Now that's a reasonable idea. Just might have the controller relay trigger a pair of relays in parallel to help prolong the life of the secondary circuit and provide a backup. Might be a bit of overkill, but I hate it when you see the temp a little above normal and realize your fan won't come on.

Thanks for the suggestion.
07-08-2012 08:51 PM
66GMC I dunno if this helps or not, but Four Seasons has a similar fan controller.
Sorry, I'm not sure how it's wired.

[Four Seasons 2011 Illustrated Guide] See page 220.

PN is 35879.
OE (GM) #19189400
More info from Four Seasons (you'll need to select the "Part Number" tab and enter "35879") including this Warning
07-08-2012 07:42 PM
LATECH
Quote:
Originally Posted by LATECH View Post
[IMG]my pictures derale.gif[/IMG]
Same circuit theory as pictured in post above. Just erase the ECM from the diagram.
The red wire is the grounding wire (counterintuitive) from the derale controller.
07-08-2012 07:39 PM
LATECH If you wire the derale ground circuit to the OE relay coil ground as I described, it will prolong the life of the controller.
If you dont have the same setup as the OP just add a relay for the fan circuit, prefferably a 40 amp bosch, and use the derale controller relay to activate the bosch relay COIL, that way the derale control will last as it is only handling a small amount of current to run the Bosch relay which is handling the Load. And the bosch job is dispensable, or at least more so as it is quite a bit cheaper than the derale unit.
07-08-2012 06:53 PM
cucumber1949 When I originally built my T-Bucket, I used the first version of the DeRale fan controller. That controller failed after two years and I replaced it with what I thought was the same controller, only to find the same issue you describe (redesigned to switch the ground side). Okay, no problem, installed the new version and move on. Controller failed again this week after be used in the car for 3 years. Both times, it appears the controller got hot and the relay had to be pried out of the controller's base. I'm running a single 2600 cfm fan which should be well within the capability of this unit. I've also installed an identical replacement fan thnking that was an issue, however unless both fans are bad it looks like the DeRale controller is 0-2 for me.

I'm thinking of trying the Painless unit (#30114 I believe) which switches the positive side of the circuit, so I'll be doing a little changing in the circuit again but it's not a big deal.
07-01-2012 09:57 AM
2x4 Barrels
try this

Hi Fcastro

I think I see the problem.You are breaking ground to control unit.Sorry this is a big no,no .Your temp sensor may be backfeeding a ground to the control and possibly causing damage.I would put that swtich in the power feed circut.Center post feed power,post1 control unit,post2 control unit and green wire.Then add a wire from ac cluch + to post2.Then you dont need a relay.

2x4s
06-29-2012 04:44 PM
LATECH
Quote:
Originally Posted by hemi43 View Post
Would grounding that wire give a false signal to the ECM ?? What I mean is that the ECM may see the the - input as a short, and put up a code.
Just my 2 cents
Thats is a great question. It may, and it may not. I am leaning towards not. There is one way to know for sure.
If it did generate a code, it would not be a "A" priority code, most likely would be a "C" or "D" priority, which would not illuminate the Engine light.
Great question. It would be handy to know the answer for sure.
06-29-2012 08:43 AM
hemi43 Would grounding that wire give a false signal to the ECM ?? What I mean is that the ECM may see the the - input as a short, and put up a code.
Just my 2 cents
06-29-2012 05:03 AM
EOD Guy X2 with Latech
06-28-2012 08:09 PM
LATECH [IMG]my pictures derale.gif[/IMG]
06-28-2012 07:58 PM
LATECH The red wire on the NEW derale diagram is the ground path, which is counter intuitive, but a ground path nonetheless. Using the first diagram for the GM part of the circuit, eliminate the OLD derale part of the diagram and using the red(counterintuitive) wire from the derale relay of the new diagram, splice it to the ground side of the cooling fan relay coil.Like I said which ever one grounds the circuit , runs the fan. Leaving the factory harness totally intact.
06-28-2012 07:49 PM
LATECH You are way overthinking this problem.
If you use the grounding path the derale controller gives to command fan on and just splice it to the ground point for the stock GM cooling system RELAY ground path, it will function properly.
The same wire that goes to the ECM from the ground side of the GM RELAY itself is where you want the derale ground to go. It wont matter if the ECM grounds the relay at 234 or the derale controller grounds it at whateverlower temp you set it too. As long as One or the OTHER grounds that circuit, the fan will run. This also eliminates the human error involved with flipping a switch if one system fails. If the Derale system fails to ground the wire to the fan relay, the GM system will act like a redundant or fail safe to turn the fan on. Simple.
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