The heater blower resistor has failed 5 times in my 99 Legacy and twice in my 96 Legacy.

I thought this was due to blower faults but no.

Sometimes the resistor wire is broken, sometimes the solder joint.

Is there any more permanent solution please?

I wouldn't mind if I could get only 2 speeds fast and slow.

Where are you getting the replacements? If its from the junkyard, stop it and buy a new one. you wont have any more issues. From what i understand they arent that pricey.

 

nipper

Where are you getting the replacements? If its from the junkyard, stop it and buy a new one. you wont have any more issues. From what i understand they arent that pricey.

 

nipper

 

Is this what would cause my blower motor to only run after the cars been on the road for 10 minutes or so? It seems to be that I've got to play with the different buttons before the blower actualy starts. It's a '91 Legacy.

Thanks,

Rob

I would look at the plug to the blower motor...chances are you have a high resistance connection there. If the motor (and resistor bank) get power and the motor doesn't start you are going to cook the resistors quickly as they are air cooled i.e. in the heater duct.

 

One warning. My experience with this common problem is with all kinds of vehicles but not one Subaru. this is an electrical issue however and i believe the wiring philosophy is the same.

 

Ted

Is this what would cause my blower motor to only run after the cars been on the road for 10 minutes or so? It seems to be that I've got to play with the different buttons before the blower actualy starts. It's a '91 Legacy.

Thanks,

Rob

 

You may want to check the resistance across the blower motor terminals and make sure its wothin spec. You can have a blower motor on its way out, then toss in tired resistor blocks, you may eat them up. Also make sure there is plenty of airflow across the block, otherwise that cause burnups also.

Check the terminals, but on my older sooby i went through three blocks in a relativly short time. Problem went away when i bought a new block.

 

nipper

You may want to check the resistance across the blower motor terminals and make sure its wothin spec. You can have a blower motor on its way out, then toss in tired resistor blocks, you may eat them up. Also make sure there is plenty of airflow across the block, otherwise that cause burnups also.

Check the terminals, but on my older sooby i went through three blocks in a relativly short time. Problem went away when i bought a new block.

 

nipper

 

OK, thanks for the tips! I'll probably have to wait till the weather gets a bit warmer, and of course at that point I won't need the heat anymore! I do have a spare, what looks like a relay - could that be the problem? It came with the car, and the previous owner said that needed replacement.

Rob

Just noticed that I've hijacked this thread...

My apologies to the OP.

Rob

Yes the blower resistor looks like a relay in a perforated metal box.

I think they burn out because either the solder used in them is too low melting point or the moisture from condensation corrodes them - the cases on old ones are always rusty. It is difficult to solder nichrome wire anyway. You would think we could come up with a better way to reduce blower speed by now - if it were on AC we could use a thyristor.

I have replaced the one in my 99 Subaru Legacy today with one that I repaired, but the one in my 96 Legacy has gone again now.

I can provide the resistance values a good one should have across its plug pins if you need it.

There must be a better way!

Gil

Yes the blower resistor looks like a relay in a perforated metal box.

 

I can provide the resistance values a good one should have across its plug pins if you need it.

There must be a better way!

Gil

 

That sounds like it. Knowing the correct values would be helpful. Thanks! How many watts is it? I'm thinking I could just solder a single resistor or two and switch to replace the factory one...

Rob

Sorry I got my stupid pin numbering wrong last time so I have edited this message -

 

Resistor values between pins of a GOOD one -

Looking at the unit with the keyway at the top and numbering the pins top left 1, top right 2, bottom left 3, bottom right 4 -

 

Between 1 and 2 3.2 ohms

3 and 4 1.2 ohms

2 and 4 2.0 ohms

1 and 3 0.7 ohms

2 and 3 2.9 ohms

 

If any of these values is open circuit the unit has failed.

 

Some of these values are for combinations of resistors AS I HAVEN'T ANALYZED THE CIRCUIT YET.

The trouble is the wattage is really high - not sure watt! - I've just thought - you might be able to multiply 12 volts by the current rating of the blower fuse? - and some people have obtained resistors from RadioShack which were ceramic coated but they failed. Others cracked open the coating to get better cooling on the wires.

Nichrome wire is difficult to solder, but the resistor ends are crimped and there is only one soldered joint between two metal parts - this has failed twice in one of mine.

I have found some units where the solder joint failed and I re-soldered with higher melting point solder.

The design is pathetic, disgraceful and old-fashioned - it might even be better to convert the DC to AC and use a solid state control.

The Part Number is 72024AA000

Gil gcleeton@hotmail.com 716 373 1015 I WILL DISMANTLE A UNIT AND ANALYZE IT FOR FOLLOWING MESSAGE - I WILL HAVE TO RENUMBER THE PINS YET AGAIN SORRY - MESSAGE FOLLOWS

SORRY ABOUT MISTAKES IN LAST MESSAGE - HERE IS THE HOPEFULLY CORRECT ANALYSIS - I HAVE A UNIT DISMANTLED HERE ON THE BENCH -

 

You can prise off the cover and twist the lugs straight underneath so you can take off the perforated screen.

With the keyway at the top, renumber the pins top left 1, top right 2, bottom right 3 and bottom left 4 (clockwise).

Inside there is only one soldered joint check this first and resolder if necessary - this has melted twice in one of my units.

All other joints are crimped because nichrome resistor wire is difficult to solder.

The circuit I think consists of 0.5 ohm between 1 and 4, in series with 1.2 ohm between 4 and 3, in series with 2.2 ohm between 3 and 2. These three resistors are therefore joined in series.

Phone me 716 373 1015 or email gcleeton@hotmail.com for a pic or help.

Sorry I got the pins wrong in last email.

What a crude unit and what a crude method of control - there must be a better way. Fancy having to force-air cool it, or the resistors would be a foot long like sausages!

Gil