93 Mustang LX - Integrated Relay Control Module replacement?

panditji · Jul 20, 2021

Hello, I'm new to these forums. Earlier this year I got a 93 Mustang LX Hatchback 4 Cylinder. I'm in Vancouver Island in British Columbia, Canada.

This week the car died on me, it cranked but didn't start. I followed an old post here, which was a godsend and was able rule out the inertia switch. I was able to use another spare battery that I have to apply voltage to the inertia switch and with that the fuel pump kicked back into life and the car started up on the first try!

So I think I've isolated the problem to be a faulty Integrated Relay Control module, the part number on that module is F1ZF-12B577-AA

I've looked for this online and can only find this on eBay at a couple of sellers who unfortunately don't ship to Canada.

Now I'm wondering what other options I might have here, I'm not super familiar with older cars in general and am not sure if these are good ideas.

One option would be for me to attempt to provide power to the inertia switch from a separate circuit. i.e. put the fuel pump on a different or the same circuit as the relay module and essentially bypass the relay module and have the fuel pump run on its own.
Attempt to take apart the relay box and fidget with it, I do have a circuit diagram that I've downloaded off the internet but wanted to check and see if it's easy to work on or if this is a good idea? I'm afraid that doing so I'll break other functionality that may have been working correctly apart from the fuel pump.

I'm open to other suggestions and thoughts on what I should do here or if there's a particular circuit that's best to hook into. Also if someone knows how to get that damned harness off the relay module, that would be greatly appreciated, I couldn't quite figure out how to unplug that on my first attempt.

Also since this is my first post, if I've got this in the wrong place happy to move this elsewhere if you folks can redirect me. Thanks.

junkyardwarrior · Jul 25, 2021

try a parts store. They were still available this time last year when I needed one. I think they called it a "radiator fan relay". Four Seasons part # 37512 if I remember right. Murray Climate Control also uses the same part number (if that number is correct). About $100 is I remember right.

And-to add, if you have a junkyard anywhere close to you take your old one with you and go look around. I actually have a Taurus IRCM on my 93 coupe (2.3L). The plug is the same, everything is the same EXCEPT the Taurus has two fan relays, one for high and one for low--and I use them both (Had to add a wire to the IRCM connector). This tells me that there may be more than one vehicle that could be a donor. Mine is a 2.3 turbo swapped, so I use a 2.3T specific computer which has a second fan output (HEDF and EDF with the former being the high speed and latter being the lower speed).

Lastly, yes you can actually take it apart. The 4 bolt holes are rivets. Carefully drill off half of the rivet and separate the cover from the housing. Then you can get to the bottom side of the IRCM circuit board and I would almost bet you'll find a burnt trace on the board. I had this issue. What you can do is solder a small piece of wire onto the board to bypass the trace and that should get you going again. I would still, however, keep a spare IRCM with you.

Option #4 is do away with the IRCM and use independent relays for each function but I don't like doing that. More work than it's worth in my opinion.

Potomus Pete · Jul 25, 2021

I don't know about this , but call me the butcher. I would think you could possibly bypass it. Cut it out maybe.

panditji · Jul 26, 2021

junkyardwarrior said:
try a parts store. They were still available this time last year when I needed one. I think they called it a "radiator fan relay". Four Seasons part # 37512 if I remember right. Murray Climate Control also uses the same part number (if that number is correct). About $100 is I remember right.

And-to add, if you have a junkyard anywhere close to you take your old one with you and go look around. I actually have a Taurus IRCM on my 93 coupe (2.3L). The plug is the same, everything is the same EXCEPT the Taurus has two fan relays, one for high and one for low--and I use them both (Had to add a wire to the IRCM connector). This tells me that there may be more than one vehicle that could be a donor. Mine is a 2.3 turbo swapped, so I use a 2.3T specific computer which has a second fan output (HEDF and EDF with the former being the high speed and latter being the lower speed).

Lastly, yes you can actually take it apart. The 4 bolt holes are rivets. Carefully drill off half of the rivet and separate the cover from the housing. Then you can get to the bottom side of the IRCM circuit board and I would almost bet you'll find a burnt trace on the board. I had this issue. What you can do is solder a small piece of wire onto the board to bypass the trace and that should get you going again. I would still, however, keep a spare IRCM with you.

Option #4 is do away with the IRCM and use independent relays for each function but I don't like doing that. More work than it's worth in my opinion.

This relay is supposed to control a few things apart from the fuel pump, I can't say for sure if those things work, i.e. if the entire thing has failed or it's just the fuel pump.

Currently the biggest issue for me is that the fuel pump renders the car non-drivable so that's the thing I want to check first. I tried ordering the replacement part from a website (the wrench monkey) but they emailed today to say that the part was out of stock.

I'm going to have to find a junkyard nearby for a replacement part but in the meantime I was wondering what I could do to get the car to be driveable in the interim.

So I'm going to give options 3 and 4 a shot.

For option 4, do you know what circuit I should attach the independent fuel relay to and if there is a standard fuel relay or a specific part that I should be looking for.

glowstang93 · Jul 31, 2021

I just recently replaced mine on my 93 due to fan and ac issues. Here is the link to what is inside. I got mine from O’Reillys. Ccrm. Control module. https://www.stangnet.com/mustang-forums/threads/constant-control-relay-module.899442/

panditji · Aug 3, 2021

Thanks everyone, I've managed to get my car running for now.
I do see the part being available on O'Reilys but I'm not in America so can't get it right now. I have family in the USA and maybe once the borders open up I'll have them bring the part to me.

In the meantime I wired up a 5 point relay to the ignition switch and tapped a fuse for power to the fuel pump.

This is definitely a little bit hacky but does the job for now. The relay provides power to the Green/Yellow wire of the ignition switch and doing this moves the Fuel Pump circuit off the Control Module.

The only thing that worries me a little bit is the fuse blowing up if the Fuel pump takes up too much power, I've not been able to find the factory specs but aftermarket pumps said that 15Amps would be adequate and that is what I'm currently using.

93 Mustang LX - Integrated Relay Control Module replacement?

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93 Mustang LX - Integrated Relay Control Module replacement?

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