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I own an 88 Turbo Coupe. The IRCM in the Turbo Coupe is a "J" version, which is somewhat different internally than the Taurus IRCM, which, if I remember correctly is the "K" version (havent looked at the IRCM in my 95 Vulcan for a few years). There are differences in the fan control circuits between the 2 versions of the IRCMs, as the Taurus has a single 2 speed fan and the Turbo Coupe has 2 separate fans. The primary fan runs whenever engine temp exceeds 215 F or if AC compressor is running. If temp continues to climb, the second fan turns on (main fan continues to run) if temp hits around 225 F or if AC high side pressure exceeds 310 psi.

I knew the guy who wrote that article. He worked as an engineer in the telecom industry and he KNEW electronics. Unfortunately, he passed away a couple years ago.
 

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Discussion Starter · #42 ·
I own an 88 Turbo Coupe. The IRCM in the Turbo Coupe is a "J" version, which is somewhat different internally than the Taurus IRCM, which, if I remember correctly is the "K" version (havent looked at the IRCM in my 95 Vulcan for a few years). There are differences in the fan control circuits between the 2 versions of the IRCMs, as the Taurus has a single 2 speed fan and the Turbo Coupe has 2 separate fans. The primary fan runs whenever engine temp exceeds 215 F or if AC compressor is running. If temp continues to climb, the second fan turns on (main fan continues to run) if temp hits around 225 F or if AC high side pressure exceeds 310 psi.

I knew the guy who wrote that article. He worked as an engineer in the telecom industry and he KNEW electronics. Unfortunately, he passed away a couple years ago.
I had a look at the cover last night and mine does have a large "J" printed on the label. What I need to do is find a way to energized the relay that controls the low speed fan and find out if I have continuity across the contacts of that relay. Relays can go bad, and where the previous fan locked up years ago it wouldn't surprise me if the relay that controls the low speed control isn't possibly cooked as well.
 

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It wouldnt surprise me if the low speed fan relay or one of the traces on the printed circuit board going to the relay contacts fried when the fan locked up. Also check the pins on the IRCM and IRCM connector for corrosion, heat damage, pushed out pins etc.

I dont remember the exact details, but years ago a friend with a Turbo Coupe had what he thought were IRCM issues. They bought a new IRCM at the Ford dealer ($$$$) put it in, and it didnt correct the issue. Further inspection found a pushed out pin on the harness connector that plugs into the IRCM. He reseated the pin and that fixed the issue.
 
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Don't forget, before opening up the IMRC, to First check the two IMRC ground wires connection atop the upper radiator support drivers side, its black disconnect connector sorta hidden about a foot below the drivers side of the upper radiator support close to the side of the radiator side water tank. Both of these grounds go to the IMRC, so if corrupt might be affecting the fan relay, or motor operation.
 
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Discussion Starter · #45 ·
Don't forget, before opening up the IMRC, to First check the two IMRC ground wires connection atop the upper radiator support drivers side, its black disconnect connector sorta hidden about a foot below the drivers side of the upper radiator support close to the side of the radiator side water tank. Both of these grounds go to the IMRC, so if corrupt might be affecting the fan relay, or motor operation.
This weekend I did have a chance to look over and inspect the IRMC and could not see anything out of place or dirty. Same with the harness that plugs into it. I did look at one ground cable that was mounted to the core support and cleaned it up a bit. The other ground which goes directly to the battery ground did not look great. I separated it and cleaned the connections the best I could. It would be nice to source a new connector and replace it. I'll check continuity through the connector and see what happens from there. If that checks out good, what else is keeping that fan from turning on low?
 

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This weekend I did have a chance to look over and inspect the IRMC and could not see anything out of place or dirty. Same with the harness that plugs into it. I did look at one ground cable that was mounted to the core support and cleaned it up a bit. The other ground which goes directly to the battery ground did not look great. I separated it and cleaned the connections the best I could. It would be nice to source a new connector and replace it. I'll check continuity through the connector and see what happens from there. If that checks out good, what else is keeping that fan from turning on low?
Low speed rad fan is done by a resistor that is usually on older ones down on the tran bell housing or engine block. They fail. Been there.
-chart-
 

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Lets think about this some more. Since you've posted that the fan motor in the recent past & the low speed fan resistor was bad & has been replaced recently & that the fan will run (but you haven't told us at what speed) but with the A/C on we assume its High speed. So what speed is the fan running when you Disconnect the fan temp sensor electrical connector????
Thus it seems to me, we can assume the High speed B+ & ground circuitry for the engine cooling fan & motor is ok.

SO, that leaves us looking at the cooling fan B+ switching, low temp sensor, the new low speed resistor & the IMRC low speed circuit B+ & B- electrical connectors pin/sockets connections, relay contacts, wiring, which includes cooked PCB raceways from the fan motor seizing up & any open fuses or fuse links in the low speed circuit????

SO, get the corrupt looking ground wire connection to the battery put right & see how it goes, or cut to the chase & rig a heavy gauge jumper wire to bypass the questionable ground wiring, to see if the fan motor resistor will run the fan on low speed. If it will then you know the questionable looking ground wiring is corrupt.

If no joy bypassing the questionable ground wiring, back up & with a heavy gauge (say #10 wire), jumper, begin bypassing one circuit component at a time, backwards from the low speed fan resistor, until you find where the fan turns on low speed & that last bypassed component belongs high up on the suspect list.
If you have, or can come by a cooling fan low speed schematic for your year / model vehicle, you'll know how many items are on the suspect list, up stream of the low speed resistor.
A bunch more thoughts for consideration, let us know what you find.
 

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Discussion Starter · #48 ·
Lets think about this some more. Since you've posted that the fan motor in the recent past & the low speed fan resistor was bad & has been replaced recently & that the fan will run (but you haven't told us at what speed) but with the A/C on we assume its High speed. So what speed is the fan running when you Disconnect the fan temp sensor electrical connector????
Thus it seems to me, we an assume the High speed B+ & ground circuitry for the engine cooling fan & motor is ok.

SO, that leaves us looking at the cooling fan B+ switching, low temp sensor, the new low speed resistor & the IMRC low speed circuit B+ & B- electrical connectors pin/sockets connections, relay contacts, wiring, which includes cooked PCB raceways from the fan motor seizing up & any open fuses or fuse links in the low speed circuit????

SO, get the corrupt looking ground wire connection to the battery put right & see how it goes, or cut to the chase & rig a heavy gauge jumper wire to bypass the questionable ground wiring, to see if the fan motor resistor will run the fan on low speed. If it will then you know the questionable looking ground wiring is corrupt.

If no joy bypassing the questionable ground wiring, back up & with a heavy gauge (say #10 wire), jumper, begin bypassing one circuit component at a time, backwards from the low speed fan resistor, until you find where the fan turns on low speed & that last bypassed component belongs high up on the suspect list.
If you have, or can come by a cooling fan low speed schematic for your year / model vehicle, you'll know how many items are on the suspect list, up stream of the low speed resistor.
A bunch more thoughts for consideration, let us know what you find.
I have confirmed a few things now that I do know for sure. The grounds are good, everywhere I probed with my multimeter all connections came up solid. The resistor is brand new, and the pins down inside the connector were also clean. I pulled the connector from the sensor that sits above the thermostat housing and the fan does turn on. I plug it back in, no fan. I have 2 IRCM's and I have opened them both and the tracers on the PCB are in good shape, no melting no burns. I am having a hard time finding a wire diagram I'll look a little more today if I get a chance. Worse case scenario is that the K2 relay is bad on both boards, I am going to look for a way to energize that relay and check continuity through the contacts. I did find that the relays are still available: BOSCH - 0-332-104-001, 0332014162 - Relay, Power. SPST NO 40A 12VDC.
 

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Ok good feedback, you've been busy on this puppy!!!

On checking goodness of the grounds with your meter, were you using the meters beeper mode, or measuring the ohms resistance of the connection, or since this is a High Amp draw circuit, were you making a preferred "under load voltage drop" measurement of the grounds????

The test Method makes a Big difference in the results we get, as a beeper, or ohms resistance measurement uses the meters 9volt battery to measure micro, or mili-amps along or across a connection & this cooling fan circuit will draw big Amps. so at only 12 volts of electrical pressure, we can be in voltage drop trouble with not much resistance in a wiring run or connection that looks close enough on a continuity test!!!
 

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Discussion Starter · #50 ·
Ok good feedback, you've been busy on this puppy!!!

On checking goodness of the grounds with your meter, were you using the meters beeper mode, or measuring the ohms resistance of the connection, or since this is a High Amp draw circuit, were you making a preferred "under load voltage drop" measurement of the grounds????

The test Method makes a Big difference in the results we get, as a beeper, or ohms resistance measurement uses the meters 9volt battery to measure micro, or mili-amps along or across a connection & this cooling fan circuit will draw big Amps. so at only 12 volts of electrical pressure, we can be in voltage drop trouble with not much resistance in a wiring run or connection that looks close enough on a continuity test!!!
Unfortunately my meter does not have a beeper so I do relay on the ohms resistance on the meter. The meter showed 0.001, up to 0.003 ohms resistance and my cables on the meter will produce that much. What is the best way to do an under load voltage drop check? Where would be the best place to hook up my meter so I can check to see what my voltages are?
 

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Here is a voltage drop mini-tutorial with simple circuit pictorial illustrations Diagnosing Voltage Drops Electrical Automotive Troubleshooting | Fluke , to sorta calibrate our vivid long term memory, so when we're under hood testing, we can sorta picture what we need to be doing test wise, to Isolate the voltage drop test we're about to make, so we're Accurately simulating the simple illustrated voltage drop test circuit, so we get accurate results.

Remember what they mention about Multiple ground points, that have More than one circuit making their ground at the same place as the circuit whos voltage drop we're trying to measure. Because for instance, electrons of electrical charge by nature, seek out the Lowest resistance path to flow, so if that ground point fastener is loose, rusty, corroded, its wire strands damaged or otherwise compromised, it can corrupt our test result. It might cause a faulty circuit to look good, because its getting its ground through another items components, or a good circuit to look wimpy, intermittent, or otherwise not just right, for the same reasons.

SO to get good believable test results we need a quality meter & careful circuit under test Isolated test set up, so our test meter, or other circuits using the same ground point don't corrupt our voltage drop test.

If all this seems to much to think about right now, if you've not already done it, re-consider my previous post #47 suggestion to confirm the Low fan speed resistor & its ground are good & work backward from there with a heavy gauge jumper lead, to bypass each item between the low speed resistor & the IMRC relay that controls the low speed fan circuit, to see which low speed fan circuit bypassed component causes the fan to run on low speed & that component would go to the top of the faulty suspect list.

Relays are a common problem part, so I agree the IMRC relays belong on the suspect list.

You keep tweaking our curiosity, by repeating that the fan runs if you Unplug a fan temp sensor, so don't keep it a secret any longer, when the fan comes on, is it on Low, or High speed & I forgot to ask last time, is it the Low or High temp fan coolant temp sensor you're disconnecting????
 

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Pic of block diag of power. There are 2 parallel grounds so best start with taking one off the body at a time, clean, sand the paint off, put anti corrosion compound on bare metal and the bolt threads. Doing one at a time will not cause the PCM to loose its memory. No risk. When starting the fender ground is primary, when Alt charging, the one to the firewall is prime. Then, cables can be weak in the crimp. That takes putting on a load and doing simple volts drop. Bad battery cable ends crimp common fail. Anything around the top of the battery is subject to corrosion as you have acid fumes venting.
-chart-
 

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Discussion Starter · #54 ·
Here is a voltage drop mini-tutorial with simple circuit pictorial illustrations Diagnosing Voltage Drops Electrical Automotive Troubleshooting | Fluke , to sorta calibrate our vivid long term memory, so when we're under hood testing, we can sorta picture what we need to be doing test wise, to Isolate the voltage drop test we're about to make, so we're Accurately simulating the simple illustrated voltage drop test circuit, so we get accurate results.

Remember what they mention about Multiple ground points, that have More than one circuit making their ground at the same place as the circuit whos voltage drop we're trying to measure. Because for instance, electrons of electrical charge by nature, seek out the Lowest resistance path to flow, so if that ground point fastener is loose, rusty, corroded, its wire strands damaged or otherwise compromised, it can corrupt our test result. It might cause a faulty circuit to look good, because its getting its ground through another items components, or a good circuit to look wimpy, intermittent, or otherwise not just right, for the same reasons.

SO to get good believable test results we need a quality meter & careful circuit under test Isolated test set up, so our test meter, or other circuits using the same ground point don't corrupt our voltage drop test.

If all this seems to much to think about right now, if you've not already done it, re-consider my previous post #47 suggestion to confirm the Low fan speed resistor & its ground are good & work backward from there with a heavy gauge jumper lead, to bypass each item between the low speed resistor & the IMRC relay that controls the low speed fan circuit, to see which low speed fan circuit bypassed component causes the fan to run on low speed & that component would go to the top of the faulty suspect list.

Relays are a common problem part, so I agree the IMRC relays belong on the suspect list.

You keep tweaking our curiosity, by repeating that the fan runs if you Unplug a fan temp sensor, so don't keep it a secret any longer, when the fan comes on, is it on Low, or High speed & I forgot to ask last time, is it the Low or High temp fan coolant temp sensor you're disconnecting????
Sorry it took so long for me to get back as I had been busy, and waiting for some decent weather. I have 2 of these relay modules. I had been switching them back and forth to see if there was a difference between the 2. I found out this weekend there is definitely something wrong with my original module as the fan nor the A/C compressor clutch would kick on when I went to ready the A/C for the season. I installed my spare unit and the fan and clutch kicked right on. To me it seems the fan runs in the low position when the A/C is running. Because it seems when I pull the plug off of the coolant sensor the fan runs faster. I am going to experiment with my original non working module and order some relays and replace them to see what happens. I opened up the module and the K3 relay was really warm, so I am thinking there is a continuity problem through that relay. The K4 relay acts like it is dead.
 

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Ok Good trouble shooting find & feedback. Sounds like you found the faulty low speed fan circuit component & maybe about to find the root cause of the remaining woes, so keep us posted on what you discover.
 

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Discussion Starter · #57 ·
Ok Good trouble shooting find & feedback. Sounds like you found the faulty low speed fan circuit component & maybe about to find the root cause of the remaining woes, so keep us posted on what you discover.
Fan runs on low speed normal with A/C, but can go to high if the high side pressure gets over some limit.
-chat-
I was finally able to replace the relays in my ICRM this last weekend. It seemed like it really improved things like start up and fuel pump performance, but I am still not getting that fan to kick on low when the engine runs up to temperature. Are there 2 thermo switches on the engine, one for low temperature and one for high, or just the one switch on top of the engine near the thermostat housing? Is there a way to either test or trip that part of the circuit to turn the fan on manually to see if it is that switch?
 
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