Engine/Transmission (1998.5 - 2002) grid heater not working???

[Dixon]

Ok here is my problem I'm having. I have a 2000 Freightliner FL60 w/ the 5. 9 engine. I have to go through a sequence of things to start the engine. I finally tired of all that and decided to check the intake heater. What I found out was that it wasn't heating up We checked the two relays that hand down from the cowling (?) and found out that the two big wires were bringing voltage to the relays but not voltate was leaving them. The relay has two small wires at the bottom and one large one coming from I guess the batterys. Would you suggest changing out the relays or hooking up some kind of wire that would be controlled in the truck? I checked the archives and might have discovered one little bit of info. I read where the intake cycles and that could cause the lift pump to not put out the same amount of pressure that it will after about 12-15 minutes of run time. I always wondered why it would be so low and by that I don't mean too low it still has about 8# of pressure on WOT. So now that you know all my issues can someone tell me what controls the intake heater? I believe the ecm is in charge and that tells the relays to relay power to the intake. I use a block heater so can I get away with just hooking up some kind of spring loaded button that I could just hold down for 10 seconds and then start the truck? One thing I have noticed is that the wts light only stays on about 5-6 seconds. Is that trying to tell me something? Thanks for the advice and this truly is a great site! ben

 

[obert]

wow. slow down there.



My first thoughts are on the relays. Yes, one of those big wires will be hot all the time, at least with the key on (battery feed for the high current supply). The other big wire should become hot when the WTS light comes on. (the relay has triggered and conncted the battery feed to the heater grid)



Now, the two small wires are the controll circut of the relay. one should go to ground, the other is the signal, which is controlled by the ECM, but i dont know if it is directly or through yet another relay. The latter would be rather complicated, but I wouldnt be suprised.

The jist of all this is get your test light out and see if the big wire to the heater is powering up when you assistant turns on the key (cold engine). If nothing there, try to figure out which little wire is the signal (find the ground and check the other one).

If there is no signal (or a short one when its cold out), my bet would be that the ECM is beeing misled by a bad temp sender some where. But realy to check anything beyond the relay, you would need to hook up the scan tool and see what the ECM really thinks is going on.



However, if you use your block heater, you can pretty much not worry about the intake heater. (how cold is it there??) I dont normaly wait for mine and couldnt care less if it worked or not. Its original purpose is reduction of "cold start smoke".



Also, our pick-ups like to be 14 or 15 psi fuel pressure. 8# isn't really panic zone yet, but check specs and keep an eye on it.



Its a mouthfull , but I hope it helps.