Charging / fuses

[sadarahu]

Thank you all for your time and advice.

OK, I looked the diagrams, but I don't think I will be able to locate all grounding points simply because there are to many of them, I have no tools, space and can't lift the car to look underneath.
In the meantime my horn went down again and the problem with charging is back again. So at this point no horn and charging Led is going On and Off. Usually when I start the engine the charging Led is ON, then when I drive for some time it comes OFF.

Here is few things I tested today:
1. Tested every single fuse (OK)
2. I pulled the 2 plugs from the fuse box under the hood and sprayed the with the contact cleaner
3. I pulled relays (3 on the passenger side and 2 on the driver side) cleaned the connectors and re-inserted.
4. I was also moving the cables (single wires) in the connectors plugs while friend of mine was observing the dashboard (if the charging will go off)
5. I cleaned battery connectors.
6. I cleaned alternator connections (the plug and the grounding cable)

Still no luck
I think I would need to go to some car shop, but I'm afraid to pick just any because most of them are simply poor quality and they take advantage of customers. I already have had one advising me to replace the alternator, but I doubt it is alternator causing the problem, as it seems to be related to the Horn as well. IT looks to me like it is connection problem. I'm on a limited budget now so I really hate to replace parts just to find out the problem is elsewhere.

QUESTION: If I have a computer tester connected - would it show any problems, or even possibly tell what is wrong ? My friend mechanic told me it will not but I do not trust his competence anymore...

Any recommended electric shop around Chicago OR shall I really go to Toyota dealer ?

Arthur