heater/ac blower motor/relay tip

[mprophet]

Well ive started on my long list of things to fix on my 96 rodeo and ive been having very little succsess until last night when i went to work on the heater/ac blower motor. The blower had quit working several months back and since i rarely used my ac there was little need for it until now since its getting colder. Anyway i did the standard checks to see where my problem was and it led me to the resister that is mounted on the side of the duct work next to the blower motor. From what ive read these resistors crapping out is fairly common but that got me to looking at it and wondering why. What seems to happen is the blower motor gets full of dust and crap and builds up resistance then in turn the resistor gets hot enough to melt the solder on its connections , it doesnt take a rocket scientists to figure out a fuse should blow before a resistor gets this hot but the engineers at isuzu must want you to replace a 20 dollar resistor versus a 50 cent fuse. Also it doesnt take a scientist to figure out that if the resistor blew it had to have a reason so i checked my fan and sure enough it was stiff as could be. I pulled the motor assembly out then remover the snap ring holding the fan blade on and then removed the two screws holding the motor inside the assembly. I then placed the motor shaft in a vise and carefully removed the motor from the plastic housing and found isuzu didnt even bother to put a bearing on the backside of the shaft instead they put a copper bushing and a felt pad ( cheap bastards ) anyway if you twist the y shaped retaining clip on the backside of the motor you can pull the bushing off clean it up with some steel wool and spray it with wd40, do the same to the felt pad or replace it with a battery cable felt pad they sell at any parts store. Blow the motor out thouroughly with an air hose then hook it up to a battery charger to see if it works. The motors shaft should spin pretty freely , now spray some more lube on the front bearing and if the motor spins pretty freely put it back in the housing and back in the car. On the resistor take a screw driver and break the plastic tabs on the sides so you can see the solder points and resolder which ever one has come loose. Reconnect it all and try it out but this time use a 15 amp fuse in the fuse box versus a 20 amp. If the fuse doesnt blow then you should be good to go if it does then your motor may be to far gone. If it does work keep the 15 amp fuse in that way maybe the next time your motor builds up crap inside it the fuse will blow versus the 20 dollar resistor.


Btw Im still looking for my temp sensor with no luck.........

[amigo-2k]

great write up! This would be nice for a 93-97 FAQ webpage .......

[mprophet]

Thanks , if anyone can think of why the 15 amp fuse would be a bad idea let me know, i did the removal last night using my interior light and a ciggarette lighter as my only way to see under the dash so its not a real complex job.

One additional note for thos with access to a lathe , if you turn a piece of aluminium with an outside diameter of the backside of the plastic housing and an inside diameter to match the id of a skateboard bearing you can pull off that bronze bearing and trow it away and replace it with a run of the mill skate board bearing which im sure would increase the life of the blower motor. I was just to lazy to turn the piece last night.

[Crystal3477]

What if your blower motor works and your AC works, but your heater doesnt work, they only way I can get it to blow at least warm air is to have it vented from the outside, which is mainly pulling its heat from the motor. Do you have any suggestions about that. Thanks
Crystal3477

[mprophet]

Sounds like a thermostat stuck open , if your blower motor works then the only thing that i would think that could cause it is a problem with the heater core or the thermostat is stuck in and open postion so your car never trully heats up. See the heater on a car is a pretty simple design , basically a radiator that is tied into your engines cooling system is placed under your dash in your duct work , the blower motor just simply blows the air across the radiator and out the vents. So your vehicle is either not getting hot or you have some sort of problem with your heater core , do you see any signs of leaking coolant on your floorboards?

[Crystal3477]

No, no signs of leaking coolant, and me and my dad even flushed the radiator system and he said he didnt see a leak then either. He said he thought it might be the thermostat as well, he doesnt think it is the heater coil though. My dad is a mechanic, but he is old school mechanic and these rodeos are a hell of a type of vehicle to try and learn the newer styles. Thanks for your input I will have him check the thermostat and and even the heater coil. Thanks again.
Crystal3477

[mprophet]

Thermostat is most definetely your problem i think its just a matter of 3 bolts and the houseing is apart, pull out the old thermostat and see if its in the closed position if its not that definetly your problem.If you want to further check it put the thermostat in a pot of water on the stove and bring it to a boil you should see the spring retract and the thermostat open up. If the thermostats the problem drop in a new one i think there about 5 bucks. There probably will be a few temperature types of thermostat when you go to buy one , if the car hasnt had a problem over heating then get a high temp one and it wont open to soon so your coolant temp can get higher thus your heater core will get higher.

If all of the these are working properly, blower motor,thermostat, and heater coil, then ther is one other possible thing that could cause this and i havent been under the dash to see how its hooked up. The switch that switches from cold to hot on your dash is most likely a mechanical switch that simply slides a door over a vent to either allow or not allow air to travel one way or another. If that switch has a broken link of some sort it wont flip the door so the hot air pases thru the heater core instead it would be blowing by the ac coils which wouldnt be on so you wouldnt get any heat and if you turned the air on to outside venting you would only get air from the engine compartment. I may have lost you on that but picture the front door on a house in the winter and you have the heat on in the house, if you open that door the heat tries to go out and the cold comes in but if you leave the door shut then the heat stays in and the cold stays out, basically the slidder that adjust hot to cold air is opening and closing that door, if the door is stuck shut then you never get the heat. Its a long shot but a possibility.

[rrhode]

I am having a similar problem but I have 12-14 volts on the positive side of the blower motor connector. The negative side does not seem to be working, if I connect this side to a chassis ground the blower motor turns. Does this sound like a bad blower switch? or a resistor pack?
Thanks
Ryan

[tygger]

Originally Posted by amigo-2k

great write up! This would be nice for a 93-97 FAQ webpage .......

Does one exist?