Fan was running on high only so I replaced the block with a used one from the same year. It then ran on all 4 speeds for approx 10 mins then I hear a pop and it now runs on high only. Possibly the used block was faulty but I suspect a short somewhere. Anyone know how I can diagnose this? There was no dectable damage to the traces on the replacement block. I'm puzzled why the fuse does not protect this?
Ok, here is the skinny from my observation of the schematics.
The AC switch position #4 DOES NOT run through the resistor block network. It is the only position that is sure to work unless you have a bad blower motor or a blown fuse. The resistor block is composed of three (3) resistors for each switch position and a small fuse. If the fuse blows or the resistor next to the fuse goes bad then no switch position will work. Otherwise, you should at least be able to operate on a lower switch setting. The problem is likely to be one or both components circled in the schematics diagram shown above. I don't know their electrical specs but I would imagine you could locate a wirewound resistor and fuse and fix it yourself.
You still will have to find out what is causing the overcurrent. And if it is not a short somewhere then it is surely that the blower motor windings are shorted out.
Hope this helps you and others out which been having similar problems.
Ok, here is the skinny from my observation of the schematics.
The AC switch position #4 DOES NOT run through the resistor block network. It is the only position that is sure to work unless you have a bad blower motor or a blown fuse. The resistor block is composed of three (3) resistors for each switch position and a small fuse. If the fuse blows or the resistor next to the fuse goes bad then no switch position will work. Otherwise, you should at least be able to operator on a lower switch setting. The problem is likely to be one or both components circled in the schematics diagram shown above. I don't know their electrical specs but I would imagine you could locate a wirewound resistor and fuse and fix it yourself.
You still will have to find out what is causing the overcurrent. And if it is not a short somewhere then it is surely that the blower motor windings are shorted out.
Hope this helps you and others out which been having similar problems.
Like I said, I don't know the resistance of these components. But consider this quick synopsis,
The fuse is rated for 20 amps at about 12 volts. Power = Amps x Volts so approximately 240 watts maximum can go through this circuit. How much wattage is the the blower motor consuming at switch position #4? That wattage would be similar to having the motor connected directly to the car battery. That would be the maximum wattage that the limiting resistors would have to be able to withstand otherwise they will "blow up". That resistor for switch position #3 is very critical and the one that possibly weakens with age due to the electrical heating and cooling cycles. Once again though, if the resistor network is getting fried almost instantly then there is something else like the blower motor that is causing the problem.
Had this problem 4 or 5 years ago with my 95 GXE. The resistor unit is in the front passenger foot well under the glove compartment. It is a flat board with stripe-type resistors and a couple (don't remeber exactly how many) solder bridges. You will see them between small metal dimples. You can easily find the broken one with an ohmmeter. In my one bridge was broken. Either cracked or separated from the dimple (bad solder). I simply re-soldered it and the problem never came back again. At most a 15 minute job.
It's few inches above where the passenger's right foot toes would be, just below of the black dome-like cover. It is the only one thing there with a connector harness that is visible. Disconnect the harness. The other side of the connector is a plastic plate held by two screws. Remove the screws and pull out the resistor block. (The plastic plate with the connector is the edge of the block.)
Had this problem 4 or 5 years ago with my 95 GXE. The resistor unit is in the front passenger foot well under the glove compartment. It is a flat board with stripe-type resistors and a couple (don't remeber exactly how many) solder bridges. You will see them between small metal dimples. You can easily find the broken one with an ohmmeter. In my one bridge was broken. Either cracked or separated from the dimple (bad solder). I simply re-soldered it and the problem never came back again. At most a 15 minute job.
"How hot does your resistor block get? I re-soldered mine and it gets almost too uncomfortable to touch after a minute of run time."
have you ever looked into the issue of resistor getting way too hot after you re-soldered it. Did you find out what the problem was..I am getting the same results...it got too hot to touch..I am wondering why...wrong type of solder..may be?
Solder has nothing to do with how hot the resistor gets. The only thing that would have an affect on it getting overly hot is the blower motor; either shorted motor windings or motor mechanically dragging.
Make sure you install the block INSIDE the blower duct before testing. It needs the cooling to operate properly. I tested mine outside the duct and it overheated within seconds. And check that any ducting is not kinked.
hmmm....are you saying that it is normal for the resistor to overheat if connected to be tested outside of the duct? and where does the cooling inside the duct come from? Does it come from the blower ? I am just confused a little? help!!!!
Had this problem 4 or 5 years ago with my 95 GXE. The resistor unit is in the front passenger foot well under the glove compartment. It is a flat board with stripe-type resistors and a couple (don't remeber exactly how many) solder bridges. You will see them between small metal dimples. You can easily find the broken one with an ohmmeter. In my one bridge was broken. Either cracked or separated from the dimple (bad solder). I simply re-soldered it and the problem never came back again. At most a 15 minute job.
Thanks so much for the tip. My 93 altima's blower resistor decided to quit working today. I cleaned the two solder bridges with flux because it's really really dirty to the point I could not desolder them with the heat gun from my rework station. After soldering the two bridges back I was able to measure all 4 connections with an ohm meter. Speed 1-3 now works great again. Cheers!
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