Why does my A/C keep blowing a fuse?

[SlantnoseSD]

I just got my system charged and installed a new A/C blower motor and it will run fine for a while but then all of a suddent he fuse will blow. Anybody have a similar situation?

[fred cook]

Is it the fuse that powers the evaporator fan motor AND the front condenser fan motor? If so, try putting one of the fan motors on a separate fuse. If one of the fan motor fuses blows than you will know which circuit to troubleshoot. Hope this helps.

[jtratza]

Try changing out the AC fuse block. My AC fuse kept blowing until I changed out the fuse block (3 fuses) several years ago. Hasn't blown since. Now if I could only get the AC to work more than 9 months a year.

[SlantnoseSD]

AC fuse box? Where is that located? The fuse that keeps bloweing on mine is located in the front trunk.

[Ken911]

thats the one I had the same problem replced the three fuse block havent blown one since

[SlantnoseSD]

Where is the 3 fuse block?

[fred cook]

If you look carefully at the fuse panel in the front trunk, you will see that there are 21 fuses. There should be a 10 fuse block, a 3 fuse block and an 8 fuse block (not necessarily in that order). I think it is fuse #19 from the front that the a/c fans are wired into. Check the connections for corrosion and/or a loose fitting fuse. Pull a new +12v hot lead from the battery, run it thru a 20 amp fuse and connect one of the a/c fans to it. If the fuse powering the evaporator fan blows, then the newly installed fan has "issues" and should be checked or replaced by the shop that did the installation. If it is the front condenser fan (most likely!) then that fan will need to be replaced. The old fuse holder blocks are somewhat notorius for causing problems such as you are having. Age and corrosion added to very small fuse contact areas are usually the culprit.

Hope this helps.

[kuehl]

Originally posted by SlantnoseSD
AC fuse box? Where is that located? The fuse that keeps bloweing on mine is located in the front trunk.

The main fuse panel is located in the front trunk
on the LH (left side) driver's side inner fender wall.

The electrical schematics are located right here
on the PP site:
http://www.pelicanparts.com/911/911_parts/911_electrical_diagrams.htm

There are a few things that can "pop" a fuse. If the fuse was not popping before you replaced the "a/c blower motor", and I'm guessing that could mean either the evaporator or the front condenser motors, then go back and check your connections to see if something is shorting to ground... such as a bare wire terminal bent against the fan motor's casing.

If you don't have a volt or ohm meter you could simply get a handful of fuses and try it the ...ahhh funky, way:
unplug the front condenser fan motor, evaporator fan motor and compressor clutch. Turn on the system and if the fuse does not pop you know its one of the three items, then simply plug each in until you blow fuse.
Not the professional approach but you'd be suprised at what can be accomplished. Other components in between, besides wires, that can cause the problem are the main ac relay in the evaporator box area (smugglers box), the front condenser fan relay, the fan speed control switch or the fan speed control resistor pack.

Let us know how you do!

[ruf-porsche]

See this link

http://www.pelicanparts.com/techarticles/mult_AC_faq/Mult_AC_faq-1.htm

or read this

A word about Fuses, circuit breakers and relays!!

For several years, the factory made the same mistake on every car with a/c. When they wired the fuse board on the '76 to about '79, they wired the Evaporator. circuit together with the Front Condenser. Fan circuit. So that all the elec. load was through ONE fuse. Well since those ceramic fuses can hardly handle 20 amps. the load of 30 or 35 amps. was way too much for them. The connectors turn blue, get loose and will actually melt. Check your car and if the second fuse from the back of the fuse board is distorted see if the red/white wire is connected with the red/yellow wire. If it is, separate them and connect one of them to the next fuse which should be empty. A very good substitute for these fuses or any fuse that seems to be overloaded (that is , gets hot ) is a circuit breaker. A c.b. can be wired with a tighter connection, won't blow at the slightest provocation, and will reset itself automatically.

Most all of these a/c's will have a Relay somewhere in the circuit mainly to protect the delicate switches from the high loads of the motors. Most over looked is the Factory relay located in the heater box next to the Evaporator.

[kuehl]

Originally posted by ruf-porsche
See this link

http://www.pelicanparts.com/techarticles/mult_AC_faq/Mult_AC_faq-1.htm

or read this


http://www.pelicanparts.com/techarticles/rice_ramblings/rice_ramblings-2.htm