garcia26233 Posted December 29, 2012 Share Posted December 29, 2012 I have a 1999 Mack Ch613 and my fan clutch won't stop. Fan clutch it's self is fairly new but I'm pretty sure that's not the problem. I suspect it's something electrical. Some times driving down the road I hear it come on and off about 3-4times per Second, like if has a faulty relay or sensor. Any ideas or clues?? Where can I find its relay or what sends the signal for it to come on and off. It's air operated, turns off when air is introduced and shuts off when it doesn't. Most of the time 85% it's on meaning it has no air in line to fan. Quote Link to comment Share on other sites More sharing options...
bullhusk Posted December 29, 2012 Share Posted December 29, 2012 I have a 1999 Mack Ch613 and my fan clutch won't stop. Fan clutch it's self is fairly new but I'm pretty sure that's not the problem. I suspect it's something electrical. Some times driving down the road I hear it come on and off about 3-4times per Second, like if has a faulty relay or sensor. Any ideas or clues?? Where can I find its relay or what sends the signal for it to come on and off. It's air operated, turns off when air is introduced and shuts off when it doesn't. Most of the time 85% it's on meaning it has no air in line to fan.I don't know if the Mack's work this way, but one of my F-Liners had a prob. like that and it was the A-C unit low on freon, even when the defroster was on and the A-C comp. would kick off an then the fan would kick off. But when the truck went up to temp. the fan would work OKBULLHUSK Quote Link to comment Share on other sites More sharing options...
staxx Posted December 29, 2012 Share Posted December 29, 2012 The A/C high pressure and coolant temp control fan drive check connections make sure a/c is working proporly also the low coolant sensor in upper surge tank are known for failing and leaking coolant into wire harness and following into engine ecu so check ecu connection for contamination also Quote Link to comment Share on other sites More sharing options...
garcia26233 Posted December 30, 2012 Author Share Posted December 30, 2012 My coolent is good and not using my a/c. It's winter time and my water won't heat enough for heater to heat properly. Quote Link to comment Share on other sites More sharing options...
staxx Posted December 30, 2012 Share Posted December 30, 2012 Just because your not using your a/c doesnt mean the a/c presure switch is having issues , the pressure switch will turn on the the fan even if a/c is off and need to check ecu module connections for contamination rust ,coolant oil , fuel . You should have 2 coolant sensors the one on the side of the water manifold is for your temp gauge on the dash the one on the end of the manifold is for the ecu that controls your fan. Check and make sure were the wires come off the sensor at the back of the head and down has not rubbed or shorted the wiring there is a clamp back there that is good at rubbing on the wires . Quote Link to comment Share on other sites More sharing options...
bigdawgmack Posted January 2, 2013 Share Posted January 2, 2013 I have the same issue with my truck, I have a 2000 CX613 E7-460. I have disconnected the pressure switch for the a/c compressor and still no change. I have also check the air solenoid on the side of the radiator to make sure it was working properly and it was. I put ground to the solenoid and the fan shut off, but as soon as I take it off the fan turns back on. I am at a loss with this one in figuring it out. Please help me on this one.Thanks. Quote Link to comment Share on other sites More sharing options...
DCR Posted January 2, 2013 Share Posted January 2, 2013 Prior to buying my 2000 CX613, E7-460,I had the truck checked out by a Mack dealer in Oregon where the truck was located. One of the problems was the fan running all the time. Service said they replaced a fuse and that stopped it. Now, 6 months later it is still operating properly. I do not know which fuse it was but I hope this is of some help. Quote Denny330-550-6020A "Mack Pack" Charter Member Link to comment Share on other sites More sharing options...
bigdawgmack Posted January 3, 2013 Share Posted January 3, 2013 Thanks Big Dog, I will look at my fuses to see if that takes care of it. Quote Link to comment Share on other sites More sharing options...
rsb502 Posted January 3, 2013 Share Posted January 3, 2013 I have the same issue with my truck, I have a 2000 CX613 E7-460. I have disconnected the pressure switch for the a/c compressor and still no change. I have also check the air solenoid on the side of the radiator to make sure it was working properly and it was. I put ground to the solenoid and the fan shut off, but as soon as I take it off the fan turns back on. I am at a loss with this one in figuring it out. Please help me on this one.Thanks.what activates the solenoid is it switched ground or switched power? if switched power activates the solenoid and grounding the post made it disengage sounds like your ground wire is bad, but I dont know if it is chassis ground or ecm return signal wire, STAXX would know. Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment Share on other sites More sharing options...
staxx Posted January 4, 2013 Share Posted January 4, 2013 The ecu is what sinks the ground to terminal b at fan solinoid , the a/c high pressure switch is normaly closed and is forced open when you have high a/c pressure in system , when it is forced open the 12 volt signal to eecu is disconnected , when ecu sees this its keeps the eecu from sinking the ground to the terminal b at fan solinoid and engages the fan fuse 41 supplies 12 volts to the high pressure switch coolant temp switch = when ecu see high temp turns fan on this is a ohms reading to ecu . Quote Link to comment Share on other sites More sharing options...
Popular Post theakerstwo Posted January 4, 2013 Popular Post Share Posted January 4, 2013 Sounds like the bridge connector from the knuter retificer to the selicone based monulated switch controler circuit has more than 10 ohms. That would be above range for the heavy duty secondary phaser senor. So my remendation is reverse polorize it for 13 milsec then open the dash and let the smoke out.If that dont get it then take it to mack. 3 Quote glenn akers Link to comment Share on other sites More sharing options...
bigdawgmack Posted January 7, 2013 Share Posted January 7, 2013 So are y'all saying it is a sensor issue or a wiring problem. I know a lot about the mechanics of the truck but I get stumped on the electrical side of it. Do one of you guys have a scamatic on how the power/ground is sent to the solenoid? Please help as I would like to get this taken care of soon!!!! Quote Link to comment Share on other sites More sharing options...
staxx Posted January 9, 2013 Share Posted January 9, 2013 Quote Link to comment Share on other sites More sharing options...
EWB555 Posted January 20, 2013 Share Posted January 20, 2013 I'm having a similar issue with my 95 E7 VMAC 1, I found this post useful however I still havent solved my issue. Bench tested the solonoid that stops the air to the fan and it works (Clicks when 12 volts applied). Fan clutch disengages when I disconnect the air line so I know it works. I tried the following procedure today to attempt to rule out ac high pressure switch:With the air pressure up and the engine cold, I turned the key on, unplugged the high pressure switch and jumped connector with paper clip, nothing happened. I think the solonoid on the side of the radiator should have clicked if the high pressure switch is the problem? also tried the same method with the coolant temp senor,and nothing happened either. The ECM on the truck has been replaced and the fan was staying on prior to replacing. I looked for the fuse however my truck only goes to number 24, I guess since its older then the one in this thread.I believe my coolant level sensor is in the water manifold towards the front of the truck, as there doesnt appear to be any wires going to the top tank (However I didnt climb up there and look at the back). Appreciate anyones suggestions on how to diagnose, fan belts keep stretching and squealing as a result of fan running all the time. I know I could easily install a manual switch on the fan, however the truck is in really good shape and I hate to bypass a factory system. Quote Link to comment Share on other sites More sharing options...
glossner8 Posted January 22, 2013 Share Posted January 22, 2013 I also had same problem on 95 cl e7-427.The sensor that operates my fan is on front of water manfold. It has two screws that conect the wires to it instead of the plugs like the two that are towards the back.I changed the sensor,and the fan solenoid,never fixed it. The two wires on the sensor one goes to the solenoid(mounted on the side of radiator on mine) and the other goes to the big ground bolt right under the starter.I took the one that goes to the ground off and ran a new wire rght to the negative post on battery.Fan works properly now,I dont know about when I start running the AC,havent tried that yet. Quote Link to comment Share on other sites More sharing options...
staxx Posted January 22, 2013 Share Posted January 22, 2013 There are big differances between vmac 1&2 fan setups and vmac 3 which is what this thread started with. Quote Link to comment Share on other sites More sharing options...
staxx Posted January 22, 2013 Share Posted January 22, 2013 But the ground for the ecu control terminates at the ground bolt under the starter on the block, and that for sure can be a issue . Quote Link to comment Share on other sites More sharing options...
EWB555 Posted January 24, 2013 Share Posted January 24, 2013 On the VMAC 1 what would be the proper diagnostic prcedure? I feel I have eliminated the fan clutch, actuator on the side of the rad, and the ECM has been replaced (for another issue, however fan stayed on before & after) Quote Link to comment Share on other sites More sharing options...
staxx Posted January 24, 2013 Share Posted January 24, 2013 Look at switch status in vmac with diagnostic reader to see what sensor is turning fan on. Quote Link to comment Share on other sites More sharing options...
Nickolashouck35@gmail.com Posted August 9, 2019 Share Posted August 9, 2019 On 1/24/2013 at 10:52 AM, staxx said: I found an open broken pressure switch on the ac condenser that was causing the fan to stay on. There is several of these normally closed switches on the a/c and temp sensor and then there is the solenoid itself the one that gives air pressure to the fan clutch. The simple way to start is just to jump these switches to check them and hot wire the air solenoid to see if it turns on and off. This is the easiest way to eliminate these things. You will very likely find a broken sensor or wire like what happened to me. Quote Link to comment Share on other sites More sharing options...
Mark jowen Posted May 5, 2021 Share Posted May 5, 2021 I have a 2000 CX613 the engine fan comes on and won’t shut off any idea why if so I shure could use some help Iv replaced everything from a/c to clutch hub 772 634 7713 thanks Quote Link to comment Share on other sites More sharing options...
Dave mac Posted April 6, 2022 Share Posted April 6, 2022 I’m having this issue with my fan as well lost ground to air switch I thought I fixed it twice by once wiggling ground wires under the starter but it came back on after 10 min next I replaced temp sensor in back on manifold again drive for 10 min it comes on and won’t shut off anything else to try Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted April 7, 2022 Share Posted April 7, 2022 What truck? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.