sloride Posted July 25, 2014 Share Posted July 25, 2014 Am I missing something with electric fan diodes. They're seperate from the fan correct? The orange plastic clip wired into the harness drivers side in front of the air box. All the auto parts stores don't list a part available. The jeep parts counter only finds a relay.. What gives? Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 25, 2014 Share Posted July 25, 2014 I had to dig for this as I was not aware there was an aux fan diode. It's a Renix-only thing and not present on the HOs since the ECU controls the aux fan switching. The diode's purpose is to prevent 12V backfeed into the aux fan relay when the the AC compressor comes on. The part number for the diode module is: 56001965, DIODE, Module, w/ Anti-Lock Brakes (Also Rad. Fan Diode). Looks like an obsolete dealer-only part. Schematic: Link to comment Share on other sites More sharing options...
Incommando Posted July 25, 2014 Share Posted July 25, 2014 So while we are here... I picked up the factory aux electric fan to supplement the mechanical only fan my non A/C '91 OBD1 4.0 has now. Is the wiring present under the air box or somewhere to install this and will the ECM trigger it by temp as I do not have A/C? Wiring it directly to a switch/relay or to a cheap thermostatic control would be OK,too. Link to comment Share on other sites More sharing options...
sloride Posted July 25, 2014 Author Share Posted July 25, 2014 Hornbrod, so I guess the only option is a JY replacement since it's an obsolete dealer part? You can't RadioShack that can you? Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 25, 2014 Share Posted July 25, 2014 So while we are here... I picked up the factory aux electric fan to supplement the mechanical only fan my non A/C '91 OBD1 4.0 has now. Is the wiring present under the air box or somewhere to install this and will the ECM trigger it by temp as I do not have A/C? Wiring it directly to a switch/relay or to a cheap thermostatic control would be OK,too. Lift the cover and look in your PDC and see if the COOLING FAN relay is present. Looking down at it from the right side it's the relay in the upper left corner. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 25, 2014 Share Posted July 25, 2014 Hornbrod, so I guess the only option is a JY replacement since it's an obsolete dealer part? You can't RadioShack that can you? What makes you think it's bad? Have you tested it with an ohmmeter? Link to comment Share on other sites More sharing options...
sloride Posted July 25, 2014 Author Share Posted July 25, 2014 No, I didn't use ohmmeter on diode. The FSM didn't elaborate how to do that. I followed the relay diagnostic in the FSM and the last bullet (d) said if this didn't work change diode. All this started with fixing the ac and now I find myself dealing with aux fan. It'll be October by the time ac is working....... I see others have hot wired their fan but I'm trying to keep under the hood as stock as possible. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 25, 2014 Share Posted July 25, 2014 If you have a DMM it's real easy to check the diode. If it checks good you cam eliminate it as the cause of your aux fan not working. If it checks bad, any 12-24 VDC diode with a 5A or so rating from Radio Shack will work since we're talking small amps in this circuit. Just make sure the diode polarity is correct (one end has a black band) when soldering it in. Link to comment Share on other sites More sharing options...
sloride Posted July 25, 2014 Author Share Posted July 25, 2014 Sweet! Thanks Hornbrod! Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted July 26, 2014 Share Posted July 26, 2014 Hornbrod, could you elaborate a little further on why the diode is needed? I know diode are like dams for electricity, allowing current to flow in one direction, but not the other. Why would it matter if the outgoing side of a relay became energized? Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 26, 2014 Share Posted July 26, 2014 Looking at the schematic, I'd guess it's there for amperage surge protection for the fan relay coil from the the higher amperage AC compressor clutch startup. Looks like another Renix kluge that seems to work, as the diode appears to be a low failure component. Link to comment Share on other sites More sharing options...
Incommando Posted July 27, 2014 Share Posted July 27, 2014 Thank you Sir Link to comment Share on other sites More sharing options...
skidoo_j Posted August 1, 2014 Share Posted August 1, 2014 I always take these every time i'm at the JY. They're great for allowing two switches to control one thing that you don't want back fed to run another. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted August 1, 2014 Share Posted August 1, 2014 I always take these every time i'm at the JY. They're great for allowing two switches to control one thing that you don't want back fed to run another. Examples? Link to comment Share on other sites More sharing options...
sloride Posted August 2, 2014 Author Share Posted August 2, 2014 Hornbrod, I checked my diode. Its a three prong or two diode type plug. It appears to have proper voltage drop for both legs with DMM set on diode and proper resistance for both legs when set for ohms. There shouldn't be any continuity, correct? Thanks. Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 2, 2014 Share Posted August 2, 2014 Look at the schematic fan diode assembly I posted. You are correct, it is a dual diode assembly with a common cathode, pin B. In order to check it correctly for forward and reverse resistance across the diodes you need to ID pins A, B, and C as shown on the schematic. Using your ohmmeter set on the "diode" symbol resistance scale, measure across pins A and B, then reverse the meter + and - leads and measure across A and B again. One reading should be infinity; the other near continuity. If this is so, the A-B diode is good.Repeat across pins C and B for the C-B diode. Also to avoid false ohm readings when checking across the assembly diodes, pins A, B, and C must be disconnected from the circuit. Link to comment Share on other sites More sharing options...
sloride Posted August 2, 2014 Author Share Posted August 2, 2014 The diode(s) are good from checking with DMM. The B on schematic says I'm supposed to have an orange with tracer wire going to cooling fan relay. Wouldn't you know it, I have an orange wire with no tracer. In other words, I have two orange wires and one grey w/tracer going to my diode plug. I haven't actually traced that phantom orange w/tr wire to cooling fan relay but I'm assuming the diode is constructed as the schematic shows with the common A in the middle of the three prong plug. (The wire color in order of appearance at the plug is Grey W/TR, orange, orange) Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 2, 2014 Share Posted August 2, 2014 I wouldn't worry about wire color. There were subtle wire color changes throughout the years and I don't know which year the wiring diagram I posted is for. Even the correct Electrical FSM for the vehicle year is not 100% accurate on wire colors. If the individual diodes check out okay, I think the diode module is fine and your problem, if you have one, is elsewhere. Link to comment Share on other sites More sharing options...
sloride Posted August 3, 2014 Author Share Posted August 3, 2014 Thanks Hornbrod. I still have a problem. I kinda figured Agnus or Lucy when they were making the wire looms at AMC ran out of the orange w tracer wire and used another orange wire to meet a quota or month end. So I'll look into ac clutch relay, if that's even related. I have the '88 wiring schematic that I've had since '89. Probably would of had it in '88, but you know how it was, get order form from parts counter, write a check, mail and wait two months. Thanks again. Link to comment Share on other sites More sharing options...
skidoo_j Posted August 19, 2014 Share Posted August 19, 2014 I always take these every time i'm at the JY. They're great for allowing two switches to control one thing that you don't want back fed to run another. Examples? Most recent I set up my coolant fan override to also relay with my elocker switch. Also have one i used on my gate controller. I just like them because the diodes are already in the nice little container Link to comment Share on other sites More sharing options...
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