Moparts Tech Archive

Elec Topics

4 or 5 pin ECU?

Kelob pie
Moparts Member
Posts: 53
From: Kewaskum, WI
Registered: Apr 2000
posted 05-01-2002 11:10 PM

Hi guys. I just bought a wiring harness for the 71 340 Cuda. It has 5 wires going to the ECU plug. Can I just use the orange box with 4 pins and be just fine? Or do I need to get a 5 pin ECU? Thanks a lot.
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Scotty
Moparts Member
Posts: 1287
From: Lumberton, TX
Registered: Nov 1999
posted 05-01-2002 11:14 PM

To my knowlege, either one will work. It won't hurt anything in the electrical if you try it and it doesn't work. It SHOULD work fine, though.
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383-man
Moparts Member
Posts: 4125
From: Balt. Md. USA
Registered: Nov 2000
posted 05-01-2002 11:18 PM

4 pin will work fine. Install it and enjoy! Ron
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DynoDave
Moparts Member
Posts: 657
From: Oxford, Michigan
Registered: Mar 2002
posted 05-02-2002 09:16 AM

Even the MP conversion kit, which come with a 4 pin orange box, comes with a 5pin wiring harness. One wire is left unused. You'll be fine.
Good Luck with your project!
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carl
Moderator
Posts: 6973
From: Ohio
Registered: Nov 1999
posted 05-02-2002 09:32 AM

Wire it and fire it, then go admire it!!!

carl
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Don1
Moparts Member
Posts: 3117
From: Valley City, ND. USA
Registered: Oct 2001
posted 05-02-2002 09:33 AM

4 pin superceeds the 5 pin brain and can be used in place of the 5 pin. The 5 pin has a separate start circuit thus the reason for the dual ballast resistor. The 4 pin combines the start run circuit and if used in replacemnet of the 5 pin uses only the run side of the dual ballast resistor. The 4 pin system uses only a single ballast resistor.
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6o4o
Moparts Member
Posts: 1146
From: Bern, Switzerland
Registered: Jul 2001
posted 05-08-2002 08:11 AM

kinda old topic but I just saw it now... I also bought a new orange ECU for my 72 Roadrunner with elec. ignition and this one has 4 pins, although my old ECU had 5 pins! (and is black). I got also a double ballast resistor!
Is that now bad that it just uses one part of the ballast resistor?
And what was original on my car? Should I get again a 5 pin ECU?
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Don1
Moparts Member
Posts: 3117
From: Valley City, ND. USA
Registered: Oct 2001
posted 05-08-2002 08:26 AM

The 4 pin replaces the 5 pin ubit and will use the run side of the dual ballast resitor. Your 4 pin should work fine. The run side of the dual ballast is very close to the same ohm reading as the single ballast resistor. In fact when a dual ballast resistor burns out on the start side the wires on each end can be wired together and the car will run fine on the other side.
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Paul Fancsali
Moparts Member
Posts: 398
From: Pittsburgh pa USA
Registered: Nov 2001
posted 05-08-2002 09:57 AM

Run the 4 pin on either 2-4 prong ballast as stated above, do not run 5 prong with a 2 prong ballast the car will not run properly. A number of years ago Chrysler was selling 5 prong control boxes with 2 prong ballast resistors, this is the wrong setup
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Don1
Moparts Member
Posts: 3117
From: Valley City, ND. USA
Registered: Oct 2001
posted 05-08-2002 10:14 AM

You can wire all 4 wires together and the car will run. That is esendially wat the 4 pin does, it elimates the start side and combines the start run to one circuit instead if a low resistance side fro start and low higher resistance side for the run side.
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6o4o
Moparts Member
Posts: 1146
From: Bern, Switzerland
Registered: Jul 2001
posted 05-13-2002 10:16 AM

I see... hmm does anyone has a scematic of the ECU itself? Wondering how that really works!
Can you still get the 5 pin ECU's and was that original on my 72 RR with elec. ignition?
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Don1
Moparts Member
Posts: 3117
From: Valley City, ND. USA
Registered: Oct 2001
posted 05-13-2002 10:57 AM

Yes 72 with original electronic ignition would have had the 5 pin. the 4 was later update. Can't remember the year but 74 or 5 I believe.
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6o4o
Moparts Member
Posts: 1146
From: Bern, Switzerland
Registered: Jul 2001
posted 05-13-2002 04:14 PM

Oh.. so you can't get the original black 5pin ECU's anymore?
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russg
Moparts Member
Posts: 403
From: Boston
Registered: Dec 2000
posted 05-13-2002 04:55 PM