HVAC blower fan not functioning - suggestions?

Prior to purchasing my 92 348 ts I had a PPI done at Bobileff Motors in San Diego and Gary indicated that the blower fan wasn't working and was probably due to a fuse being melted. I had him do the major and then brought the car back to fix the fuse. $250 later I'm told it isn't the fuse, they suspect the electric fan motor has gone bad; they hooked up DC current to it directly and it did not function. I'm also told the motor resides inside a sealed unit and replacing it is "cost prohibitive." Gary suggests cutting the plastic unit open, fixing the motor and then sealing it back up. Since I want to drive the car I say no, I'll worry about getting it done later.

So Sunday I decide to do some digging on my own - to my pleasant surprise, a Phillips screwdriver and a 10mm wrench are all that is required to open the "sealed unit" and remove the electric motor/fan assembly. After I pull it, I hook it up to a 12 volt DC unit and guess what - it runs fine (and yes, I'm an idiot for not checking that BEFORE pulling it...) I'm not bagging on Gary, I'm 100% satisfied with the major they performed, just a little perplexed at their diagnosis on this issue.

So here is where I am at:
- Confirmed electric motor/fan assembly is functional;
- Ran diagnostic mode on A/C & heater control unit - no error codes, appears to be functioning correctly;
- Digital multimeter on +/- wires to fan unit shows no current (checked with motor running, fan speed cycled through all settings);
- Grounded multimeter directly to chassis and performed same test as above to rule out poor ground;
- Checked HVAC fuses and relays - all OK

So the electric motor is functional, it's just not getting any current. Lack of current does not appear to be related to a blown fuse or relay. And the A/C control unit happily informs me the fan is at full blast on the LED.

My next step is going to be pulling the A/C & heater control unit out of the cockpit to try Stabilant 22a and reseting the ECU in the device - searching through F-chat seems to indicate a lot of gremlins get resolved in the unit this way. Any suggestions on what I should be checking next, or does this seem like the next logical step?

 

Actually, I have YOU to thank for that No Doubt! Most of what I've done so far in regards to troubleshooting has been from info from your resource site. I've swapped out relays and I've pulled the fuses and visually inspected them. I like your idea to check the voltage on both sides of the hidden fuse (not so hidden anymore with all the trunk trim pulled out). I'll perform a few more tests on the wiring and replace fuses even if they look good before I pull the A/C unit. That's an inexpensive exercise, and I don't want to contemplate shelling out $2,100 if I mess something up on the A/C control.

 

Tonight I replaced the fuses and swapped out relays (again). Now I'm getting current and correct voltage to the connector for the fan. The fuses I pulled all look good, and this is the second time around for the relay swap - but I'm not complaining, for some odd reason it works now. I'll order new relays since I suspect one of the relays is going bad and faults from time to time (perhaps in conjunction with a fuse that was corroded and limiting voltage). Interestingly the hidden fuse wasn't a problem since the previous owner did the funky "hook up subwoofers to the air duct system" stereo install and the troublesome fuse was replaced with an updated assembly in the process of moving the relay bus bar.

I should be able to get the rest of the system re-assembled and recharge the A/C lines this weekend and test it all out. I'll try to get some pics to detail the troubleshooting process so hopefully the next person who has difficulty with the fan unit has an easier time diagnosing and correcting than I did. I've got about 6 hours invested in this (so far), but knowing what I know now this would be a 1 hour job up to this point. It's all easy in hindsight...

 

I appreciate your frank comments; fortunately we do have a number of choices in Southern California for both dealer and independent servicing. I was satisfied with the major service - the mechanic, Eric, invited me into the shop and spent considerable time with me to explain and go over everything he was doing while the engine was out in front of us. I am disappointed in their initial mis-diagnosis during the PPI and repeated mis-diagnosis of this issue on follow up and I plan to address it with Gary, the owner. I don't know much about electical systems (just enough to be dangerous) and I was able to sort it out with relative ease - I expect much more when I am paying top dollar for an "expert" to work on the car. To be fair they have several mechanics there and I'm not sure who did the PPI or looked at the fan problem - Eric seemed quite competent and I want to avoid forming opinions (and voicing them here) until I've talked to Gary. And thank you for the information/advice on the relays - I was not aware they were servicable.