Virgil Posted April 18, 2021 Report Share Posted April 18, 2021 We just got a 65k miles Cmax 2013 and as you might as well guessed it, it has the drain issue. Now to be honest I did not know about this issue prior to buying it and we took it to Form, 500$ later a new 12v battery and battery plug, what ever the hell that is, we were told the car is fixed. We drove the car from Montreal to San Diego with no issues. Now every few days the car decides to not turn on. As an engineer I decided to figure out the issue myself. If you measure the power on the low voltage battery is 4.3v and draining still. Nothing in the car was on so yes F79 is what made sense to pull first. The voltage stopped dropping, after checking more, turns out that ACM is draining the power. The issue is that this part is buried under the dam dash, so no go for simple fix. However if we look at fuse 79 is controls - Voice control module, radio, navigation system, DVD player, CD changer, door lock button . I dont understand what door lock button is because Fuse 66 also controls Driver's door lock, double locking . In any case the simple solution at this point is to compliably disable F79 when they car is off, now this sucks as you get to lose all your cool stuff, like presets i guess. But i would rather not have presents than no power on the car. In any case this relay fuse will do the trick Amazon Link . You will have to replace the 30A with a 15A, than remove fuse 79. Connect left pin from Fuse 79 to line 30 on the relay. Than Fuse 61 to Relay 30. This way the relay will turn on when the cart starts. And the ground to ground. This will now turn on fuse 79 only when the cart starts. Quote Link to comment Share on other sites More sharing options...
cr08 Posted April 18, 2021 Report Share Posted April 18, 2021 Get the ACM updated by a dealer. There have been TSBs for this exact issue on other Ford models over the years with software updates to fix this exact issue. No need for a rube goldberg workaround with the fuse. fbov 1 Quote Link to comment Share on other sites More sharing options...
jzchen Posted April 24, 2021 Report Share Posted April 24, 2021 (edited) Hi, and welcome to the forum! (Do you happen to be a transportation/automotive lighting guru that I know from another forum)? I agree with @cr08. Ford has a fix for battery drain issues on '13 models, which was the model year we had owned. It included some form of firmware/software update, plus wrapping some tape around the rear door harness (that I can somewhat remember). I hope that they still offer to fix it for free, as it's a known issue for that model year. EDIT- I don't know if/think you lose your radio presets, maybe the current radio station. (Or am I confused with another vehicle)? Edited April 24, 2021 by jzchen Quote Link to comment Share on other sites More sharing options...
EricG60626 Posted January 16, 2022 Report Share Posted January 16, 2022 Virgil, Don’t listen to the naysayers. I like the way you think. Like only ten thousand other people, my 2013 C-Max has the F79 circuit drain problem. I recently brought to Fox Ford in Chicago where ($165 diagnostic fee later) I was assured the problem was a loose cable on the battery and not a drain. Less than 2 days later, dead again. Grr. In the past, the radio failing to turn off was the symptom which told me to pull the F79 fuse and allow the system to reset. But in my car, apparently, that no longer is a reliable indicator of when the drain is occurring. If the dealer promises to make a genuine effort and read the service bulletins, perhaps I will bring back. But just in case, I am kluging together my own solution – Splice a cut-off switch and ammeter into a fuse extension. Anytime I see current flowing after the car is turned off, I will open the switch and (hopefully) allow the system to reset. Quote Link to comment Share on other sites More sharing options...
stolenmoment Posted January 18, 2022 Report Share Posted January 18, 2022 I bow to your superior search skills! I looked for one of those awhile back and never found it! Quote Link to comment Share on other sites More sharing options...
SnowStorm Posted January 19, 2022 Report Share Posted January 19, 2022 On 1/16/2022 at 4:22 PM, EricG60626 said: Splice a cut-off switch and ammeter into a fuse extension. Anytime I see current flowing after the car is turned off, I will open the switch and (hopefully) allow the system to reset. Hold on ... that one is for ATO fuses (0.75 inches wide). It looks like we have the so-called Mini fuses (0.43 inches wide). I think the correct item should be this one (don't know why it's 50% more!). As stolenmoment says, they are hard to find. Quote Link to comment Share on other sites More sharing options...
beeewell Posted December 31, 2022 Report Share Posted December 31, 2022 (edited) On 4/18/2021 at 7:42 PM, cr08 said: Get the ACM updated by a dealer. There have been TSBs for this exact issue on other Ford models over the years with software updates to fix this exact issue. No need for a rube goldberg workaround with the fuse. Can anyone confirm that getting the ACM updated actually fixes the drain problem? I read in another forum that it's questionable whether or not Ford ever had a successful fix for it. Edited January 4, 2023 by beeewell Quote Link to comment Share on other sites More sharing options...
Gohatters Posted April 13, 2023 Report Share Posted April 13, 2023 On 12/31/2022 at 6:34 PM, beeewell said: Can anyone confirm that getting the ACM updated actually fixes the drain problem? I read in another forum that it's questionable whether or not Ford ever had a successful fix for it. it fixed mine for a few years. Maybe not coincidentally I took my 2013 sel to ford for the recall a few weeks ago and the battery drain problem just happened again for the first time since I got it fixed. Quote Link to comment Share on other sites More sharing options...
mikekoz Posted May 11, 2023 Report Share Posted May 11, 2023 Our Cmax Energi Has been pretty much dead since October of 2022. Our local repair shop replaced the 12V battery in it and it was OK until just after Christmas. I brought it back to them about a month and a half ago and they reprogrammed the modules, whatever they are! Worked fine for 10 days, then back to deadsville! This past Sunday I removed fuse 79 and charged the battery, and so far it has not died. I may try this workaround if just removing the fuse fixes the problem. If it does, and I cannot figure out how to install this relay, I could always get a bluetooth speaker and play music while I drive from my phone! Everything else on the touch screen seems to work. We really do not want to bring the car to the dealership. It has done this a few times during the 8-9 years we have had it and may just end of selling it if I cannot get it running. Quote Link to comment Share on other sites More sharing options...
C-MaxA2 Posted May 13, 2023 Report Share Posted May 13, 2023 Find a good Ford dealership (look on line in Yelp, etc.) and get them to sort out the issues. A 'local repair shop' doesn't have the access to all the technical stuff; just whatever rumor their local mechanic might have heard, somewhere. cr08 1 Quote Link to comment Share on other sites More sharing options...
mikekoz Posted June 4, 2023 Report Share Posted June 4, 2023 I guess we will have to take it to Ford. After almost 4 weeks, the car just died again! ? I searched for a recall that would fix this problem, but did not find anything. Does anybody have an idea what Ford would charge for fixing this problem? Our car is long out of warranty and we really do not want to put much money into it. Quote Link to comment Share on other sites More sharing options...
cr08 Posted June 4, 2023 Report Share Posted June 4, 2023 On 6/4/2023 at 4:43 PM, mikekoz said: I guess we will have to take it to Ford. After almost 4 weeks, the car just died again! ? I searched for a recall that would fix this problem, but did not find anything. Does anybody have an idea what Ford would charge for fixing this problem? Our car is long out of warranty and we really do not want to put much money into it. Cost shouldn't be much. The update takes 10-15 minutes tops. So likely it'll be the cost of a 1/2 or hour of labor depending on how they want to charge you. Quote Link to comment Share on other sites More sharing options...
mikekoz Posted June 5, 2023 Report Share Posted June 5, 2023 Thanks, but that post does not describe the problem we are having. I will call Ford and see what they have to say then make a decision from there. I do appreciate the help! Quote Link to comment Share on other sites More sharing options...
cr08 Posted June 5, 2023 Report Share Posted June 5, 2023 It may not list the exact symptoms you experience, but it's all related. A dead 12v battery will often happen after experiencing those symptoms if it is left unchecked. Worst case you can fib to the dealer and say some of this is happening and provide them that TSB. The update called for should resolve it long term. Quote Link to comment Share on other sites More sharing options...
Newbie Posted September 9, 2023 Report Share Posted September 9, 2023 @Virgil Hi, any chance you could post a crude diagram of how you wire the relay. Couldn’t really understand how 79 and 61 both go to 30 on relay. Quote Link to comment Share on other sites More sharing options...
countryfit Posted December 8, 2023 Report Share Posted December 8, 2023 i had a drain issue on a 14 energi and dealer updated a firmware (whatever they said they did). my wallet was $550 thinner. it was good for about 1 year then backed to day one. going to pull 67 and 79 to test. Quote Link to comment Share on other sites More sharing options...
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