1983 Mustang Heater Fuse

[foot2floor]

Looking for guidance - I added factory A/C to my car by swapping the heater box and used all the existing factory wiring (which was in place with the heater only system but not used).

Things seem to be working fine but I keep blowing the 15 amp fuse. Got to looking at the diagram on LMR's site (which I've posted below) I see the list fuse 9 as 15 | 30amp...

Does anyone know if its okay to put a 30amp fuse where their used to be a 15 amp fuse because I've added A/C???? Besides the Compressor Clutch, what else is drawing power? Don't want to burn the car down but that's how I read this diagram.




-------------------------------------------LMR gets all credit for this image and fuse chart -----------------------------------

Number	Amperage	Description
1	15	Stop Lights, Hazard Warning Lamps, Speed Control
2	6	Circuit Breaker: Windshield Wiper/Washer System
3	N/A	Not Used
4	10	Exterior Lights, Instrument Illumination, Upshift Relay Coil
5	15	Turn Signal and Back-up Lights
6	20	Air Conditioning Clutch, Heated Rear Window Relay Coil, Trunk Release, Speed Control, Clock, Lights out Warning
7	N/A	Not Used
8	15	Courtesy Lights, Ignition Key Warning Buzzer, Fuel Filler Door Release
9	15 | 30	Heater | Air Conditioning System
10	20	Flash To Pass
11	15	Radio, Premium Sound
12	20	Circuit Breaker: Power Door Locks
13	5	Instrument Illumination
14	20	Circuit Breaker: Power Window
15	N/A	Not Used
16	20	Horn, Cigar Lighter, Clock
17	N/A	Not Used
18	10	Carburetor Circuits, Dual Timer Buzzer, Tachometer, Turbo Boost Indicators, Warning Indicators, Low Fuel Warning

[massacre]

If it were me, i would upgrade the wiring to bigger wires to handle the 30 amps, and then it should be fine.
But pulling 30a through wiring designed for 15a is just asking for trouble.
Just my opinion

[foot2floor]

If it were me, i would upgrade the wiring to bigger wires to handle the 30 amps, and then it should be fine.
But pulling 30a through wiring designed for 15a is just asking for trouble.
Just my opinion

That's my point however... How do I know? The car had all the wiring in it for the A/C system. I'm wondering if the fuse panel and associated wiring is ALSO the same...and only the fuse is different???

[massacre]

[foot2floor]

For anyone who will read this thread in the future... The factory 1983 wiring in the fuse box and down is rated for 30 amps with or without AC. I am still using the non ac wiring harness and fuse box. Adding the AC heater box and controls was easy. Let me know if you have any questions.

[at_the_junkyard]

I ran into the same thing a few years ago when I upgraded to factory AC in my sons 80 cobra. I think the extra draw is mostly because of the larger blower motor on the AC cars.

I replaced the 15A with a 30A fuse. Its been his daily driver for several years and I can confirm no issues with wiring or fuses since etc.