coladylan Posted October 28, 2011 Report Share Posted October 28, 2011 Hey guys, When i switch my heater to level 3, my heater turns off. It works like it is suppose to on 1 and 2 but not in 3. Both my 82 and 83 have that problem What is causing it to do it? and more importantly, anyone know how to resolve the issue? Quote Link to comment
datzenmike Posted October 28, 2011 Report Share Posted October 28, 2011 All I have is a picture of the dropping resistor for a 620 . The 720 fan switch connects different values of wire resistors to give different speeds. Anyway, these coils of wire get hot so they are mounted inside the motor and fan assy so the airflow keeps them cool. The 720 ones are on the fan motor below the glove box roughly in the upper left I think. There will be 3 or 4 Blue wires going to a plug in the housing. There should be at least a Blue/White, Blue/Black and a Blue wire, maybe more if you have the 4 speed motor. If you can't find it I can take a picture of mine tomorrow. I can't remember how you get at it, maybe pull the bellows hose off that goes to the heater and look in? Probably one of the coils is broken. Quote Link to comment
Buzzbomb Posted October 29, 2011 Report Share Posted October 29, 2011 I'm going off of memory here...I had the exact opposite problem. What I had was NO 1 or 2, and it worked fine on 3. When I took my heater control resistor out, I'm fairly certain that 3 did not involve the spring. It was fixed, so to speak, and that's why I had 3 but no 1 or 2. I fixed mine by simply adding the screw in the above picture. I think mine was a factory defect. I now have 1, 2, and 3 thanks to a .10 screw and DatzenMike's pic :D Gotta love Datsuns! It's super easy to take out, but you have to be careful with it because it's plastic. Look for the oval plastic plug looking deal with the wire hook up next to the blower motor. Just ease it out with a flat blade screwdriver and take a look at it and if you have any sort of mechanical aptitude, which you must because you own a 30 year old truck :), you'll be able to figure out how this works. Maybe there is some corrosion on the 3 part? Could be something simple. Like I said, get the resistor unit (DatzenMike's pic above) out of there first and you'll probably be able to see the problem. Quote Link to comment
coladylan Posted December 19, 2011 Author Report Share Posted December 19, 2011 okay so i finally got around to looking into whats wrong. I pulled the fan and motor, and the resistor plate. The resistor plate looked fine and there was no corrosion or broken pieces. In the fan there was a rats nest, but now that is all clear. BUT even after clearing the nest, the switch still stops at 3. Is there any other normal things that go wrong? Maybe in the switch itself? Everything looks fine except it does not work. Sooo any other ideas? Quote Link to comment
wayno Posted December 20, 2011 Report Share Posted December 20, 2011 okay so i finally got around to looking into whats wrong. I pulled the fan and motor, and the resistor plate. The resistor plate looked fine and there was no corrosion or broken pieces. In the fan there was a rats nest, but now that is all clear. BUT even after clearing the nest, the switch still stops at 3. Is there any other normal things that go wrong? Maybe in the switch itself? Everything looks fine except it does not work. Sooo any other ideas? I would go to a wrecking yard and get a 3 speed switch and resistor, then put the new resistor in first as it is easier, if that don't fix it, then unplug the switch and plug the replacement in without pulling the existing switch, try the new switch while it is just hanging there, you may have to remove the tray, but that is easy compared to replacing the 3 spd. switch. Quote Link to comment
coladylan Posted December 20, 2011 Author Report Share Posted December 20, 2011 ya I went and priced a brand new heater resistor plate, and it was like $8 so I'm gonna get one and then move on from there... hopefully its the plate and it just isn't working for some reason. Time shall tell Quote Link to comment
ggzilla Posted December 20, 2011 Report Share Posted December 20, 2011 Why go to all that trouble? Use an ohmmeter to test the resistors. If they have continuity, it will do you zero good to buy a replacement. But if you find one has no continuity, buy a replacment. Quote Link to comment
coladylan Posted December 20, 2011 Author Report Share Posted December 20, 2011 Good idea... I might try that. BUT i might just buy a new one anyway since its only $8 and move from there. Your way does make the most sense though, and uses a much better and easier check off method thank you. Will keep posted on what happens Quote Link to comment
dreadsiren Posted December 21, 2011 Report Share Posted December 21, 2011 you can even visually inspect your switch... pull off the little selector boots, remove 2 screws (on either side of the heater selector shield) pull the shield off and look at the underside of the switch, the solder is usualy burnt if its the switch (had to replace 2 on my 4 720's) make sure there are no splices or shorts on your power wires to the heater so it doesn't fry a new switch once it is installed. one 720 I had the prev owner tried hooking up a sterio off the main heater power wire... not only did the radio not function with out the heater on it fried the switch, relay, melted fuze to box and fried motor... made it so I got the truck for cheap though, lol) Quote Link to comment
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