Fan for A/C and Heater just quit - need help

One of the resistors that control the fan needs to be replaced.

Possibly the resistors pack that controls the fan needs to be desolder and soldered.

The easy DIY things are checked out - sounds like time to get it fixed under warranty.

Mike

I have an 1998 Accord and the fan switch ran on only one speed. I thought the switch had broken. I was dreading having a dealer or mechanic pull the dash apart to rplace the switch.

It turns out the the plastic on the fan speed knob (female connection) had cracked. I pulled the knob off (pull towards you)and replaced it (slide a new knob on) and the fan was fine. I have all 4 fan speeds. This does not explain your heat or AC? ??

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There is no resistor pack in that model, but rather a rectifier-driven thing,. Thank goodness Honda also put in the 'full speed switch' for such an event. The speed dial might be dead, or the terminal corroded. The part that varies the speed is just inside the heater, beside the fan and can be seen looking in over the glove box. (or at least you see the screws that hold it in place) Might have to drop fan out bottom.(easy) If there's RUST inside there, you've probably had problems with damp carpet during rainstorms, right?

'Curly'

Probably an H-bridge power MOSFET. And probably has a thermal protection.

Hi, Actually the car has been well taken care of without any water damage. 26 K miles We're the original owner. Where is the fuse for the fan? The reason is I have checked all the colored looking fuses, but maybe the fuse is one of the non colored things. Or there is this black plastic box, to the left of the main fuse box on the firewall in the engine compartment. I didn't know if these were fuses or not. The fan only blows on the over-ride high setting but the A/C compressor doesn't engage or heater either, even in the override high mode with the fan blowing. It does not blow cold air. Thanks again for all your advice and any help you can give us. Karen

What the heck would you need an H-bridge for? To reverse airflow and pump it out of the passenger compartment? :)

One of the resistors on my resistor pack (88 Civic) died and I replaced it with a MOSFET (no H-bridge, just a single one) and a little controller that outputs 0..100% PWM, for smooth fan control. Yeah, a bit overkill, but it was fun project :)

LoL. Shouldn't we assume that they make cars for smokers. :-)

Did you go with an N or P-Channel MOSFET? Let me guess, N-Channel.

Good point

Yeah, N-channel in a low side configuration. I actually fitted the MOSFET and its heatsink onto the piece that usually the resistors are mounted on to. It was a bit trickier than I thought; try switching a 10A inductive load without really being able to tap into the circuit. (I wanted to make it a drop-in for the resistor pack; didn't want to mess with re-wiring the entire blower, partially because it would have been a bit of a pain, and partially because I didn't know ahead of time whether it would actually work

I usually don't design power electronics (not anywhere near) but it was a fun thing to do. Went through several revisions and only blew one single FET. Mightily proud of myself, I am

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Deservedly, too!