HVAC fuse blown

kermit · Post by **kermit** » Mon Feb 09, 2009 3:04 pm

I got in the truck the other day and went to turn on the heat, but the switch was already on high and no air was coming out of any of the vents. I checked the fuse and sure enough it was blown. The replacement fuse immediately went out as well. I know its an extremely broad question, but any ideas on what could be blowing the fuse?

Thanks

roadrunner · Post by **roadrunner** » Mon Feb 09, 2009 3:07 pm

Bad/stuck blower motor?? Shorted wires?? If on defrost perhaps compressor/safety switch problem?? Perhaps Brule will have some other ideas.

04crewvt · Post by **04crewvt** » Mon Feb 09, 2009 3:07 pm

OK I'll bite, a short?
Seriously though did the fuse blow as soon as you replaced it? I assume you shut the HVAC off before putting in the new fuse. More details would help us out a lot.

kermit · Post by **kermit** » Mon Feb 09, 2009 3:11 pm

haha... I know its a vague question. I turned off the truck before I replaced the fuse. I didn't know if there were any common problems with the HVAC that I might need to check.

04crewvt · Post by **04crewvt** » Mon Feb 09, 2009 3:15 pm

If you replaced the fuse with the HVAC still on but the truck off you didn't learn anything but that starting the engine caused the problem. I would check the blower motor resistor first.
Chevrolet S10 HVAC Blower Motor Resistor Delco
Parts Number : AC15-71991
MFR# : 15-71991
Description : HVAC Blower Motor Resistor
About $12.00

kermit · Post by **kermit** » Mon Feb 09, 2009 3:26 pm

after a closer look. I got it to blow again, but not until I turned the fan on 4. If I am looking at this right, the belt is running, but the pulley isn't turning. It comes and goes... bad relay somewhere?

04crewvt · Post by **04crewvt** » Mon Feb 09, 2009 3:31 pm

That's classic symptom of the resistor going bad it uses the resistor to provide a higher draw when the blower needs to run on high. Are you talking about the AC pulley under the hood? it's on a clutch and only engages as needed.

kermit · Post by **kermit** » Mon Feb 09, 2009 3:34 pm

even before the fuse went out, there was no air coming out of the vents. would a bad resistor still explain that?

04crewvt · Post by **04crewvt** » Mon Feb 09, 2009 3:38 pm

If there was no air on the lower settings as well then I would look to the blower motor itself, it may indeed be seized up. Have you heard any squealing or howling from it? My old Chevy would howl when cold, the bearings were going bad, it would stop once it ran for a while at least until it seized completely and I had to hit it with a hammer t free it.

rlrnr53 · Post by **rlrnr53** » Mon Feb 09, 2009 8:25 pm

My experience has been that usually you will hear some type of noise before a motor goes out. I'm not saying that it can't happen, just not common. I have had pencils, pens or sticks to foul the squirrel cage and stop the motor. The newer full size trucks have had problems with the resistor melting the connector.

kermit · Post by **kermit** » Tue Feb 10, 2009 4:02 pm

funny that you say that... i found a carpenter's pencil wedged under the fuse box. where is the motor located? is it easy to get to?

roadrunner · Post by **roadrunner** » Tue Feb 10, 2009 6:48 pm

I have not done it for quite a while but years ago some people had so much trouble with kids (and careless adults too) leaving pencils etc on dash boards that some had me install 1/4" mesh or smaller screen under the dash cover to prevent entry of foreign objects into the defroster openings. Seemed to work pretty well for those who needed it.

kermit · Post by **kermit** » Mon Feb 16, 2009 2:56 pm

Finally got under the hood over the weekend and took out the blower motor... sure enough it was stuck. I pulled out the resistor and it didn't have any visible signs of going bad. Once i had the motor loosened up i turned the a/c on, but the fan only worked on 3 and 4. Since the resistor didn't look bad, I took a look behind the switch inside, but didn't see any signs of arcing.

The blower motor works, but only on speeds 3 and 4. Should the switch or the resistor have visible damage if they were bad?

04crewvt · Post by **04crewvt** » Mon Feb 16, 2009 3:02 pm

Check both sides of the connector for a melted or scorched mark, that is commonly found when they go bad. I would also check the switch for the same scorched/melted issue, otherwise since it's apart a $16 part is worth installing to see if that's the problem. Might as well pick up the new motor as well once it has seized it's only a matter of time before it happens again.

Post by **HenryJ** » Mon Feb 16, 2009 3:06 pm

Test it with an ohm meter.
I would bet the motor has too much resistance and slower speeds and doesn't function properly until higher voltages are applied.
I would suggest replacing the blower motor before it takes other components down with it.
"Freeing" one up does not usually last long. A bandaid when a better fix is needed.

kermit · Post by **kermit** » Mon Feb 16, 2009 3:18 pm

before i took it apart i unplugged it and tested it with a new motor and it only worked on 3 and 4 as well, which made me question whether or not it was the right motor. The one i tested didn't have a male connection for the hose that comes out of the bottom of the motor . I am going to check another store to make sure i find the right motor.

i've still got some tinkering to do...

Post by **HenryJ** » Mon Feb 16, 2009 3:24 pm

Ok, so I guess you are working with a new motor. Use an ohm meter , or continuity meter to test the resistor.
If it is good then check the switch.