Fuse #18 blowing and no odometer? Try this...
10-26-2015, 09:17 PM
#1
1994 F-150 4X4 5.0 XL
Thread Starter
Fuse #18 blowing and no odometer? Try this...
I have a 1994 F-150 that was having an airbag code 22 flash all the time. I replaced the sensor behind the passenger seat below the rear speaker ($40.00) and the next code appeared - 34, which is the air bag in the steering wheel. I didn't believe that ALL of the components in the airbag system were bad, so I took apart the ACM and found the thermal fuse - a white and black block on the edge of the PCB - had at some point melted beyond repair to protect the remainder of the system. I went to the salvage yard today and bought a used ACM for $35 and visually checked that fuse before I left the yard - all appeared good! After installing it in the truck I turned the ignition on and waited for any codes to flash - uh-oh - no light at all! I put the old module back in - still no light and no odometer either now. I went into panic mode thinking I blew up something else, but took a step back and looked everything over...
What I found wrong with my odometer not showing any numbers (backlight was fine) was the Airbag Control Module had a short inside, causing the 10 AMP fuse to blow in position #18. Apparently this will also give you trouble with the transmission and speedometer. The actual part that failed is MOV1 in the ACM, located just below the rectangle thermal fuse. If you take an ohmmeter and measure across this component with the ACM out of the truck (follow the proper procedure to disarm the air bag first!), you "should" read somewhere around 2 MegOhms. If you unsolder it from the circuit board, a good one will read Infinity or Open on your meter. If you read a short circuit, zero ohms or have continuity (tone) on the MOV, it has failed for some reason. I was lucky enough to be able to take the old board MOV and solder it into the replacement board, replace the 10A fuse, and start the truck with no codes and the ACM passing all tests.
I have not researched the MOV to find a replacement yet, but I would expect Mouser or Digi-Key to have an equivalent part (if I find one, I'll post an update or reply here).
With these vehicles getting older and the same for the electronics, I am going to replace the capacitors inside the ACM to prevent any future problems. They are called electrolytic capacitors (they look like little cans) and do have a life expectancy of 20 years or so. They do not like heat too much and with the ACM being near a vent in my truck and probably yours too, the heat has probably shortened their life by drying them out (there's eleven total). A sure sign to know if they have failed is you will see that the top of one or more have swelled or there will be leakage around them. Mine don't show either of these, but I also know that their values will change over time and could be what was causing my old ACM to give out false readings. If you choose to do the same, I want to caution you that they do have a polarity to them as well as different values - pay special attention to what and how you take them out and replace them with (they must match)! These can also be bought from Mouser or Digi-Key, or even a local electronics or TV repair shop I'm guessing (support your local guy!).
I hope this might help someone troubleshoot a blown #18 fuse (especially after a leaky windshield) and save you lots of aggravation. No need to remove the instrument cluster or remove sensors from the transmission just yet - disconnect the 2 harnesses going to the Airbag Control Module (black and blue box under the center of the console) and replace that 10A fuse. If it doesn't blow, you found your problem. Just safety the airbag first! Good luck.
What I found wrong with my odometer not showing any numbers (backlight was fine) was the Airbag Control Module had a short inside, causing the 10 AMP fuse to blow in position #18. Apparently this will also give you trouble with the transmission and speedometer. The actual part that failed is MOV1 in the ACM, located just below the rectangle thermal fuse. If you take an ohmmeter and measure across this component with the ACM out of the truck (follow the proper procedure to disarm the air bag first!), you "should" read somewhere around 2 MegOhms. If you unsolder it from the circuit board, a good one will read Infinity or Open on your meter. If you read a short circuit, zero ohms or have continuity (tone) on the MOV, it has failed for some reason. I was lucky enough to be able to take the old board MOV and solder it into the replacement board, replace the 10A fuse, and start the truck with no codes and the ACM passing all tests.
I have not researched the MOV to find a replacement yet, but I would expect Mouser or Digi-Key to have an equivalent part (if I find one, I'll post an update or reply here).With these vehicles getting older and the same for the electronics, I am going to replace the capacitors inside the ACM to prevent any future problems. They are called electrolytic capacitors (they look like little cans) and do have a life expectancy of 20 years or so. They do not like heat too much and with the ACM being near a vent in my truck and probably yours too, the heat has probably shortened their life by drying them out (there's eleven total). A sure sign to know if they have failed is you will see that the top of one or more have swelled or there will be leakage around them. Mine don't show either of these, but I also know that their values will change over time and could be what was causing my old ACM to give out false readings. If you choose to do the same, I want to caution you that they do have a polarity to them as well as different values - pay special attention to what and how you take them out and replace them with (they must match)! These can also be bought from Mouser or Digi-Key, or even a local electronics or TV repair shop I'm guessing (support your local guy!).
I hope this might help someone troubleshoot a blown #18 fuse (especially after a leaky windshield) and save you lots of aggravation. No need to remove the instrument cluster or remove sensors from the transmission just yet - disconnect the 2 harnesses going to the Airbag Control Module (black and blue box under the center of the console) and replace that 10A fuse. If it doesn't blow, you found your problem. Just safety the airbag first! Good luck.
10-29-2015, 08:58 PM
#2
1994 F-150 4X4 5.0 XL
Thread Starter
FOLLOW-UP...
The airbag system is working fine since the repair. I just tried to locate the MOV online and I can't seem to find a direct replacement. Littlefuse makes automotive MOV's, but there are many different varieties to choose from. If you replaced your ACM recently with a rebuilt unit, is there any chance you could tell us what MOV is installed in there? I'm thinking the part is either distributed to Ford only, or is outdated so far that even the datasheet can't be found. What my original shows is...
06113
FOOF-AA
T D K
...It's the dime-shaped component right next to the black & white thermal fuse block. Mine is colored black. If we can get a part number off of a newer unit, we can hopefully cross-reference it to a part on Digi-key for easier replacement.
Thanks for helping with our repairs!
z-man1
The airbag system is working fine since the repair. I just tried to locate the MOV online and I can't seem to find a direct replacement. Littlefuse makes automotive MOV's, but there are many different varieties to choose from. If you replaced your ACM recently with a rebuilt unit, is there any chance you could tell us what MOV is installed in there? I'm thinking the part is either distributed to Ford only, or is outdated so far that even the datasheet can't be found. What my original shows is...
06113
FOOF-AA
T D K
...It's the dime-shaped component right next to the black & white thermal fuse block. Mine is colored black. If we can get a part number off of a newer unit, we can hopefully cross-reference it to a part on Digi-key for easier replacement.
Thanks for helping with our repairs!
z-man1
10-08-2016, 06:35 AM
#3
Member
Zman,
A year later, I have the same issue on a 94 F150. Popping #18 when turning ignition to ON position. Pulled out ACM and found the MOV1 cracked. I do not have tools to deep test. Similar searching as you did for a replacement MOV was a failure. Too many automotive MOV's.
MOV #
04053
F00F - AA
TDK
The F00F-AA is indeed an indicator that this MOV is especially made for FoMoCo. It is, in Ford parts parlance, an engineering number prefix and suffix. If only the actual # was included, such as F00F-xxxxxx-AA. The 04053 is probably a batch code or possibly a date code. Such as 04 - 4th month: 05 - 5th day and 3 - 1993. Or similar. Who knows?
Testing the MOV while still on board, in my particular instance, OHM's zero out. Visibly, the MOV is cracked and obviously shorted. I do not see any other damage on the board.
Anyway, that's my story ... I'm now looking for another ACM.
Chap
Addendum: As a point of interest the F00F prefix indicates an initial model year of 1990. The "F" is decade, meaning 90's and the "0" is year of decade 90's. Like the eng # on the module housing F2VF, the "F2" indicates 1992, the "V" is for Lincoln Continental Town Car, the last "F" is a catch all letter usually found in ALL engineering part numbers by Ford regardless of make or model.
A year later, I have the same issue on a 94 F150. Popping #18 when turning ignition to ON position. Pulled out ACM and found the MOV1 cracked. I do not have tools to deep test. Similar searching as you did for a replacement MOV was a failure. Too many automotive MOV's.
MOV #
04053
F00F - AA
TDK
The F00F-AA is indeed an indicator that this MOV is especially made for FoMoCo. It is, in Ford parts parlance, an engineering number prefix and suffix. If only the actual # was included, such as F00F-xxxxxx-AA. The 04053 is probably a batch code or possibly a date code. Such as 04 - 4th month: 05 - 5th day and 3 - 1993. Or similar. Who knows?
Testing the MOV while still on board, in my particular instance, OHM's zero out. Visibly, the MOV is cracked and obviously shorted. I do not see any other damage on the board.
Anyway, that's my story ... I'm now looking for another ACM.
Chap
Addendum: As a point of interest the F00F prefix indicates an initial model year of 1990. The "F" is decade, meaning 90's and the "0" is year of decade 90's. Like the eng # on the module housing F2VF, the "F2" indicates 1992, the "V" is for Lincoln Continental Town Car, the last "F" is a catch all letter usually found in ALL engineering part numbers by Ford regardless of make or model.
Last edited by Chap150; 10-08-2016 at 06:42 AM.
10-11-2016, 07:30 PM
#4
Member
To follow up, I received the "new" used ACM today, plugged it in and the #18 fuse folly is finally fixed! I think I will locate another ACM and keep it in stock, just in case. 
Chap
Chap
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Last edited by Chap150; 10-12-2016 at 08:21 AM.
10-11-2016, 08:22 PM
#5
1994 F-150 4X4 5.0 XL
Thread Starter
Glad to hear your problem is fixed Chap - congratulations! I'm still doing well with my replacement ACM too. Now if we could only source more of those white & black fuses or MOV's, we'd be able to repair these modules for next to nothing.
I still think it would be worthwhile to replace all of the capacitors in these units - after 20+ years of heat and cold they're gonna fail sooner or later. Might be a great winter project!
...z-man1
I'm still doing well with my replacement ACM too. Now if we could only source more of those white & black fuses or MOV's, we'd be able to repair these modules for next to nothing. I still think it would be worthwhile to replace all of the capacitors in these units - after 20+ years of heat and cold they're gonna fail sooner or later. Might be a great winter project!
...z-man1
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Chap150 (10-12-2016)
11-10-2019, 08:28 AM
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Hell, I am aware that i need to find the ACM in my 1995 ford F150 xlt 5.0 v8. But after a full day of looking I am not sure where it is located. Would you be able to tell me where it is located?
11-11-2019, 10:00 PM
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Ford calls it the Airbag Diagnostic Monitor (ADM), and it's the blue plastic module wrapped in dark grey foam (that's peeling off) above the gas pedal. Why are you trying to find it?
(phone app link)
(phone app link)
(phone app link)
(phone app link)