Air Conditioning Electrical issue
 

I've run into an A/C issue that I'm hoping I can get some input/assistance with.

Earlier this week while driving home from work the Charge light came on in the cluster. Troubleshooting let us (me and my indy mechanic) to the alternator not properly charging the battery, so replaced the alternator with a new 140 amp unit and new drive belts. Initial test drive went well so we thought it was back to normal.

When driving it to work on Friday night the dash climate controls stopped working entirely. Everything went black and I couldn't even get the fan on. I checked fuses and found fuse 48 (7.5A) blown. Replacement got everything working again, but I didn't test drive it before going to bed.

This morning my daughter borrowed the car to run a couple of errands and the same thing happened. Dash controls went dead. I haven't checked the fuses yet, but am guessing that 48 is blown again.

What other components should I check? Something is obviously popping this fuse as I know it's just a symptom, not necessarily the cause. :dunno:

I've had the truck less than a month, so I'm not totally familiar with what would fail here, or where else to check. Thanks for any pointers.

This is the only thing wrong with it at this point (aside from teh factory in-dash tape deck that needs to go away).

Just off the top of my head I would first have a look at the compressor clutch wire to make sure it hasn't rubbed through or been damaged.

F48-Heating and A/C Control Module
According to my fuse info, all models use F48 the same way. Someone here can shed more light on what is a heating and A/C control module.

So I'm guessing there's nothing else on that circuit? I'm just trying to figure out why the heating and A/C control module would cause the fuse to blow now, when it was working fine up until I swapped out the alternator. :confused:

What brand alternator did you buy? Was it actually new or rebuilt? Did someone put a multimeter or similar on it after installation to check voltage?

A cheap cig-lighter voltmeter off Amazon is a very handy thing to have..

The module has probably 30 wires coming out of it. wpoll is the guy to post wiring diagrams. :rofl: He's helped me a lot with pictures. :thumbup:

There is nothing else on that fuse F48 circuit. It only supplies continuous (Terminal 30) voltage for AC control panel (IHKA).

Thanks for that confirmation! I thought that must be the case.


I work nights (and weekends) so this is taking me a while to troubleshoot. Good thing this isn't my only car.


So far I know that putting in a new 7.5A fuse they blow again almost immediately after the AC control panel comes on. I tried a 10A fuse (I know, don't do that.) but it blows immediately too. I dug out my multimeter and will check how much is actually going through there. I'm betting something in the harness in the dash has rubbed through and is grounding out that control panel. On Monday I'll tackle that.


I can't confirm the brand of the alternator. My indy mechanic got it for me. We did go through two because the first one was making a grinding noise when connected. He's not open again until Tuesday, so I'll swing over there then and see what other information he has on it, but I'm kind of betting that correlation isn't causation here.

The IHKA (A/C panel) controls multiple devices and so the power being fed to any of these may be the "current sink" that is blowing the fuse. Without an internal panel circuit diagram (never seen one) it's a little hard to say exactly where this current is going but I'm not a big believer in coincidences so... have a good look around engine bay near the alternator area - there's a few items close by that could be an issue if damaged.

My #1 suspect is the supply wiring to the auxiliary water pump. It is powered directly via the IHKA and is right by the alternator... :rolleyes:

The main components IHKA is giving voltage supply:
*AC compressor magnetic clutch
*water valves
*aux water pump
*washer nozzle heating