CATEGORY LISTINGS > CATERPILLAR > 3406E fan problems [ REFRESH ]

Thread Title: 3406E fan problems Created On Tuesday June 02, 2009 11:21

mttruck Posts: 10 Joined: Jun 2009

Tuesday June 02, 2009 11:21 I am having an issue that my fan does not come on automatically. It works with the pressure of the a/c when it is engaged, and it works with the switch, when I hook it up to the computer the ecm is showing that the fan is already on. I have replaced the CAT wire harness as well as the thermostats cause they were bad. We are figuring that it could be an oem issue but not sure how to test it, our local dealership can't seem to find the problem either. Any suggestions?

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mttruck Posts: 10 Joined: Jun 2009

Thursday June 18, 2009 13:08 We have run a few more tests such as changing fan control in the ecm, but that has not done any good. As I said before the ecm shoes that the fan is on any time the computer is hooked to the truck, running or not. I also have a truck with a c12 that does the same thing. It is getting pretty hot here in NM and we run local in town, any suggestions would be greatly appreciated. We have talked to Cat dealer and mechanic locally with no help, besides Pete dealership locally also with no help.

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westcoast Posts: 982 Joined: Dec 2008

Thursday June 18, 2009 16:07 First off , when you plug in to the ecm it,s telling you that your fan is enabled - not on , start truck build up air -turn truck off - turn key on -you should hear your fan clutch disengaging if so that means your ignition and enabling relay are working , if not work from there , Is it a horton or kysor fan set up and what vehicle Regards David ------------------------- detroit

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mttruck Posts: 10 Joined: Jun 2009	Sunday June 21, 2009 11:28 It is a horton. On a 99 Pete 379. When we start the truck and then turn it off, then turn the key back on the fan clutch does not disengage. Only if the fan switch is flipped from auto to manual. Where might I find the relay that you talked about. Thanks.
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westcoast Posts: 982 Joined: Dec 2008	Sunday June 21, 2009 21:33 Go to your fuse/ relay panel , you,ll find engine power relay then brakesaver relay and next to it is your fan enable relay - Circuit 239 is ground wire off the relay- Circuit 522 is fan disable off the relay -Circuit 220 is fused 10 amp off the relay and 226 is Ignition power (fused ) Regards David ------------------------- detroit
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mttruck Posts: 10 Joined: Jun 2009	Monday June 22, 2009 06:10 I don't find these relays in my fuse panel. Horn, marker lts, bunk a/c, left, cl lps, right, comp clutch, cab fan low, fresh/recrc are the only relays that I have. Also didn't find circut 522. This truck had a sleeper that was removed, could this be part of my problem? Thanks
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desertstormboy Posts: 372 Joined: May 2008

Monday June 22, 2009 22:40 if it works with the a/c, then you can rule out the actual fan clutch and the valve on the firewall because its working. only time it doesnt work is when its running hot right? probably the temp switch on the engine. if et is saying the fan is on when it actually isnt, then check the wiring from the temp sensor to the ecm. could be sending wrong information to the ecm. check the status screen and see what temperature it is reading. check that reading with the gauge in the dash. should narrow it down for ya. ------------------------- IT WENT BING BANG BOOM!

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desertstormboy Posts: 372 Joined: May 2008	Monday June 22, 2009 22:43 another thing is what is your temp gauge reading? is it actually getting hot enough for the fan to kick on? usually around 210 degrees. any check engine lights coming on, or are you just seeing it at 200 and thinking its too hot? i have seen some go to 217 before kicking on. run it til it gets hot. ------------------------- IT WENT BING BANG BOOM!
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desertstormboy Posts: 372 Joined: May 2008

Monday June 22, 2009 22:45 sorry for all the threads, but things keep coming up in my mind. i dont know your mechanical skills, or anyone elses...sometimes i question my own.....when you hook computer up, you say it says fan is on.....is the auto/manual switch on, causing the reading of fan being on? always start with the small stuff...dont just go changing water pumps, and thermostats..... ------------------------- IT WENT BING BANG BOOM!

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mttruck Posts: 10 Joined: Jun 2009

Wednesday June 24, 2009 08:20 The switch is in the off position, if you flip it while on the status screen nothing happens. It still shows fan as on. I have talked to my local Cat place and Peterbilt place and the Cat guy says that it is a oem issue not a Cat issue. We changed the thermostats because they were bad, as well as the wiring harness because it had a bunch of broken wires right at the plugs, easier to change it than try to solder or crimp the wires. Less time consuming too. When the truck hits about 200 or 205 a warning buzzer and light comes on. But after talking to local Cat guy, we ran the truck and the temp warning light and buzzer came on at around 200 to 205, we kept the truck running to see if the fan would come on at higher temp, and ran it until the shut down and check engine light came on about 220, still no fan came on. We flipped the manual switch and it came on and cooled the motor pretty quickly. The temp gauge and the computer are within 2 degrees of each other. We have changed the sending units, in the thermostat housing also. The only other thing we have thought of is this truck had a sleeper at one time, is it possible that there is a sensor or relay related to the sleeper that could be affecting the fan control?

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JoeZ Posts: 938 Joined: Dec 2008

Wednesday June 24, 2009 13:46 I can't see where removing the sleeper could have anything to do with it. I seem to remember a problem like yours once and it turned out to be a grounding problem with the fan relay. It may have even had two relay's on it.....can't remember. I would check with Pete and get a picture of the fan relay or relays. That will give you an idea what to look for. ------------------------- One of the last 2 Stroke mechanics left. 44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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marc7242 Posts: 254 Joined: Sep 2008

Wednesday June 24, 2009 17:12 Are you sure if the fan is actuated off the ECM using info from the engine temp sensor or weather there is an old-style thermal switch that grounds the relay for the fan solenoid? Paccar trucks can run behind the times on this, some even had capillary tube temp gauges still in '99. Use a wiring diagram to figure out which wire from the ECM actuates the fan relay. Can't remember if it supplies a voltage signal or closes a ground, you should be able to tell from the wiring diagram. Carefully backprobe this pin and see if it is indeed doing what it is supposed to do. I'm pretty sure the way these work is there is a consant 12V to the control coil on the fan relay with the key on. From there, if you close any one of three paths to ground it will energize the relay. The three paths could close through the manual switch, the A/C switch, or a single wire thermal switch that closes a path to ground. Most trucks work by requiring air pressure and voltage to release the fan- keep that in mind- voltage at the fan solenoid usually means that fan is released (free-wheeling) marc

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marc7242 Posts: 254 Joined: Sep 2008	Wednesday June 24, 2009 17:18 One more thing came to mind. I saw once when someone had the thermostats out, they pulled the fan switch and teflon taped it. The tape kept switch from grounding because its a one-wire switch that ground through its case marc
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mttruck Posts: 10 Joined: Jun 2009	Thursday June 25, 2009 10:20 I am still not able to find the relay, it isn't in my breaker box. Where is it? I am in the process of tracing wires but you know how that is. Will keep looking. Thanks.
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JoeZ Posts: 938 Joined: Dec 2008	Thursday June 25, 2009 15:37 Like I said.....get a picture from the Pete dealer.....that usually helps to find it. The last one I remember being on the firewall someplace..... ------------------------- One of the last 2 Stroke mechanics left. 44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.
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mttruck Posts: 10 Joined: Jun 2009	Friday July 10, 2009 14:40 Now for an update, We finally found where the relay goes in the dash, but it wasn't there so when we put a relay in the slot it turned the fan on and now the manual switch doesn't work. The fan is on all the time. Other suggestions? Fixed but not completely. Thanks.
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marc7242 Posts: 254 Joined: Sep 2008

Friday July 10, 2009 18:16 Someone has been playing with this thing- check for wiring, sensors, etc that don't look factory- Someone did something at some point to get the fan to work the way it was. From here you would have to troubleshoot the fan relay. Three things should energize (or de-energize) the relay- engine temp getting hot enough to turn the fan on- A/C demand- or manual switch demand. You'll have to figure out how the whole system works- air to release the fan or to apply the fan? from there does the relay supply power or take away power to apply and release the fan? you can figure this out by unplugging the solenoid and relay to see what happens. On a standard 5 pin relay, pin 30 is power, 87A is power out with the relay de-energized (remember 'a' for 'always'); pin 87 has power when the relay is energized. To energize the relay, you need a power and a ground at pin 85 and 86. Its an electromagnet, so polarity doesn't matter. This is called the control coil and simply switches power from 87 to 87A when energized (think of a relay that controls low beam-high beam). The relay is controlled by having a constant power and switched ground or vise versa. You just have to figure out how yours works marc

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mttruck Posts: 10 Joined: Jun 2009

Saturday July 11, 2009 15:53 Ok now we found that 522 was broken between ecm and relay, voltage reading at ecm is only 9.0 volts, and the relay won't switch with anything less than 12 volts. When the relay is plugged in the fan won't disengage. 522 is the wire to make it disengage. Is this an ecm programing problem or a parameter that needs to be changed. The voltage going in to the ecm without the engine running is 12.7volts and with the engine running is 14.2. With the engine running the voltage at 522 in the ecm is 0 where the relay goes is also 0. Why does the voltage drop when the engine is running?

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marc7242 Posts: 254 Joined: Sep 2008

Monday July 13, 2009 16:35 I believe the ECM can be programmed for the type of fan clutch, air on or air off. Let it get up to temp and see if the fan shuts off when it should be turning on - if you can get the temp that high with the fan stuck on. If not take the relay out to get it up to temp. As for the voltage reading, it may be closing a ground. Remember your meter reads voltage potential (difference between two points). If you have one lead on a ground and the other lead on the ground side of the load, you'll see 0 volts. You see 12 with the engine off because the circuit isn't complete and you'll have 12 volts up to the point when the circuit breaks. marc

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AZDieselman Posts: 57 Joined: Mar 2007	Tuesday August 18, 2009 20:44 Hello, Where you able to fix this truck? I am just beginning to diagnose one (97) with the same problem. The wiring diagram I got from Peterbilt isn't very helpful, the only relay I see in the fan circuit is R9, but the dealer says my truck doesn't use it. I've checked all the usual suspects, and everything appears OK. I'll spend more time on it tomorrow. Kevin
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mttruck Posts: 10 Joined: Jun 2009	Wednesday October 28, 2009 14:33 We haven't fixed it still trying to figure out what the problem is, I think now it is the programming from pete on the ecm but not sure and haven't had a chance to put it in the shop to be checked. Have you fixed yours?
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AZDieselman Posts: 57 Joined: Mar 2007

Wednesday October 28, 2009 20:18 YES. I got it fixed a few weeks ago. It just took some concentrated effort. I checked the ECM, and output #4 was enabled. This controls the fan. I slowly traced the wiring up into the dash, I found the fan solenoid relay. The relay was OK. The battery power to the relay was missing, I checked the fuse panel and didn't find any bad fuses. I connected an OHM meter to the the relay and checked each terminal in the fuse panel. I found that the fuse spot labeled ACC, was missing it's fuse. I installed one and the fan came on. It will come on at 206 and off at 196. I double checked all the wiring and found nothing else. It would have been nice if Peterbilt had labeled this fuse location. I'll help you, if you can't get it. Kevin

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mttruck Posts: 10 Joined: Jun 2009	Thursday November 12, 2009 13:41 Thanks Kevin, Now we found where the relay was supposed to be and it was missing, after putting a relay in the spot, the fan comes on and runs all the time. All of the fuse spots have a fuse in them, also we have a fuse block in the dash and when you pull the third fuse out the fan turns off.
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AZDieselman Posts: 57 Joined: Mar 2007	Friday November 13, 2009 17:05 Leave the other relay out. Check your power and ground to the relay. Mine was getting power from the ECM, but not from the fuse panel. I had to physically follow the wires. The ECM will provide around 12 volts with the fan off, and about 4 volts with it on. Kevin
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