ac/heat doesn't turn off and drains battery, which fuse?

[osote]

OK, I noticed that the ac/heat doesn't turn off and that is what is
causing the battery drain that makes my battery run down every night
unless I pull the fusible link before I go to bed and hook it back up
in the morning before I drive it.

What fuse goes to the ac/heat on a 91 subaru legacy wagon and is it in
the main box inside or in the engine compartment?

 

[Edward Hayes]

Owners manual?? or start pulling fuses one by one.

 

[« Paul »]

OK, I noticed that the ac/heat doesn't turn off and that is what is
causing the battery drain that makes my battery run down every night
unless I pull the fusible link before I go to bed and hook it back up
in the morning before I drive it.

What fuse goes to the ac/heat on a 91 subaru legacy wagon and is it in
the main box inside or in the engine compartment?

Do you mean the interior "blower motor"?
Do you mean "high speed" if you meant "blower motor"?
If so, most cars have a blower motor relay that sometimes gets it's
contacts welded closed. On a 91 Subaru... I am not sure.

 

[osote]

Do you mean the interior "blower motor"?
Do you mean "high speed" if you meant "blower motor"?
If so, most cars have a blower motor relay that sometimes gets it's
contacts welded closed. On a 91 Subaru... I am not sure.

I don't know for sure what the word is for what I mean. The A/C OFF
button is pressed in but you can hear the fan going and if you slide
it from 1 up to 4 it blows harder even when the OFF button is clearly
pressed in.

How do the relay contacts get welded closed and how can I fix this?

I tried pulling the 2 heater fuses and the main fan fuse and the damn
thing still worked!

 

[osote]

Do you mean the interior "blower motor"?
Do you mean "high speed" if you meant "blower motor"?
If so, most cars have a blower motor relay that sometimes gets it's
contacts welded closed. On a 91 Subaru... I am not sure.

I don't know for sure what the word is for what I mean. The A/C OFF
button is pressed in but you can hear the fan going and if you slide
it from 1 up to 4 it blows harder even when the OFF button is clearly
pressed in.

How do the relay contacts get welded closed and how can I fix this?

I tried pulling the 2 heater fuses and the main fan fuse and the damn
thing still worked!

 

[« Paul »]

I don't know for sure what the word is for what I mean. The A/C OFF
button is pressed in but you can hear the fan going and if you slide
it from 1 up to 4 it blows harder even when the OFF button is clearly
pressed in.

How do the relay contacts get welded closed and how can I fix this?

I tried pulling the 2 heater fuses and the main fan fuse and the damn
thing still worked!

Usually there is only one relay and it is for high speed operation.
Current draw at high speed may too much for a dash switch and so a
relay is used. HOWEVER... that does not sound like your problem because
you can change blower speed. Isn't your A/C off button only for the
compressor and not the blower? Most (all???) cars that have that button
use it to turn the compressor on and off, only. Could Subaru route ALL
fan power through the relay? I don't know. Relays sometimes get burned
contacts due to excessive current draw or wear.

 

[JW]

(e-mail address removed) wrote:


Usually there is only one relay and it is for high speed operation.
Current draw at high speed may too much for a dash switch and so a
relay is used. HOWEVER... that does not sound like your problem because
you can change blower speed. Isn't your A/C off button only for the
compressor and not the blower? Most (all???) cars that have that button
use it to turn the compressor on and off, only. Could Subaru route ALL
fan power through the relay? I don't know. Relays sometimes get burned
contacts due to excessive current draw or wear.

Being an electrical engineer, I am astounded by the foolish routings of
electrical circuitry in the Subaru! I love the car but what is the reason
the cruise control is routed through one of the horns? Or why is the
heater motor routed through the other one! I had a gas tank full of rust
and found out the next years tank Which I found to replace it, although
all the connections were all identical, blanked the digital dash. I had
to change the float in the tank to make the dash work again!

 

[CompUser]

Being an electrical engineer, I am astounded by the foolish routings of
electrical circuitry in the Subaru! I love the car but what is the reason
the cruise control is routed through one of the horns? Or why is the
heater motor routed through the other one! I had a gas tank full of rust
and found out the next years tank Which I found to replace it, although
all the connections were all identical, blanked the digital dash. I had
to change the float in the tank to make the dash work again!

And why modulate panel brightness by varying
resistance *to ground*....weird! 8^B

 

[SteveG]

I don't know for sure what the word is for what I mean. The A/C OFF
button is pressed in but you can hear the fan going and if you slide
it from 1 up to 4 it blows harder even when the OFF button is clearly
pressed in.

How do the relay contacts get welded closed and how can I fix this?

I tried pulling the 2 heater fuses and the main fan fuse and the damn
thing still worked!

You are not approaching this right, looking for a quick fix rather
than understanding what you are doing. The blower fan should work
whether or not the A/C is on. The main fan is the main coolant fan,
not the heater-A/C blower fan.

It would be best if you purchased a workshop manual that included
wiring diagrams, but as was suggested some time back you might be able
to make some progress without them if you would follow the good advice
previously given. Place an ammeter between the battery and ground and
test each circuit individually for a current draw by removing one fuse
at a time. If you find one that drops the current, that circuit is the
likely problem. Then you'll have to examine that circuit and the items
on it, which might or might not be easy without a circuit diagram, but
at least you'll know at that point whether you'll need one.

Proceeding methodically is what is needed here.

Good luck,
Steve

 

[John G]

You are not approaching this right, looking for a quick fix rather
than understanding what you are doing. The blower fan should work
whether or not the A/C is on. The main fan is the main coolant fan,
not the heater-A/C blower fan.

It would be best if you purchased a workshop manual that included
wiring diagrams, but as was suggested some time back you might be able
to make some progress without them if you would follow the good advice
previously given. Place an ammeter between the battery and ground and
test each circuit individually for a current draw by removing one fuse
at a time. If you find one that drops the current, that circuit is the
likely problem. Then you'll have to examine that circuit and the items
on it, which might or might not be easy without a circuit diagram, but
at least you'll know at that point whether you'll need one.

Proceeding methodically is what is needed here.

Good luck,
Steve

It would not seem as though an ammeter is really required if he can hear
the fan running when it should be OFF.
All he has to do is find the control that is not controlling it and fix
it.
Puling the fusible link stops it.
Then find the actual fuse that stops
Then find the switch or relay.
Elementary my dear Watson.