I need electrical wiring assistance

[DennisG01]

This is a follow-up post to my earlier one about my power mirrors not working. I looked into this a little further and I found that I was getting 12v at the small, black, 2-wire connector before the power mirror switch (PMS for short

[tommac95]

The OEM Helm manual indicates many diodes are interspersed throughout the wire harness. GMCTD advised that one was in the vicinity of the AC compressor; don't know location of others....although their existence is strongly hinted at by curious resistance readings taken occassionally.

There are 3 primary types of 'passive' components in electric circuits: resistors (engineered bad connections) inductors (coils) , and capacitors (aka 'condensors' , caps are simply containers comprised of two insulated plates , separated from each other by an insulator, and connected to either the input or output lead-wire, respectively). Diodes are a fourth passive component [and a semiconductor junction] and they have a straightforward function of acting as an electric 'check-valve' , allowing current to pass in one direction thru it , blocking current passage in the other direction. When connected to an ohmeter they measure both high and low resistance, depending on their polarity in the test circuit.

Suggest start by rechecking the resistance of the unknown ('Device Under Test') in both directions {always assure at least one side of the component is disconnected from circuit when checking}. /Your meter may incorporate a 'diode test' function, if so, use it./

Diodes are incorporated in circuits switching "inductive" loads {those comprising coils} because when a coil has its' connection to power switched "OFF" , a 'back emf' pulse of electricity is generated , the voltage of which can exceed the original supply voltage, and be in opposite polarity, hence frying delicate connected devices.] See electromechanical contact point-condensor ignition circuitry.]

If these unknown devices appear to be diodes, inspect to see if there's a ring of marking around one end of the cylindrical housing, this should confirm. This mark indicates polarity ... expect the marks to be on opposite sides from the device, as the current will only course thru each and the device in turn.

Two replacement sources:
http://www.mpja.com/listitems.asp?dept=112&main=110
and: http://digikey.com/

* * *
My electric mirror doesn't function. I think it has frozen mechanically due to rust/corrosion. Interested to see what you find ....

[DennisG01]

Thanks, Tom. This particular "device under question" does look different than any other diode I've ever seen (although I've only seen ones that are black, perfectly cylindrical, and have a silver band on one end). But, I'll check resistance going both ways later tonight when I get home.
Thanks!

[BUZZ]

I suspect these are Pico fuses, to protect the mirror motors from overload. They have numbers on them, what they say?
Go to littelfuse.com, do a series search upper right hand of site and type in 251 they may look familar.
http://www.littelfuse.com/cgi-bin/r.cgi/index.html
Buzz

[DennisG01]

I checked resistance both ways - same results.

Buzz - That picture looks just like what I have. The markings on what I have are as follows:

There is a big "L" with a little "F" that is sort of inside the "L". Next to that is "1A" which I assume is for 1 Amp. I came up with this part number: 0251001.MRT1 but, it says it's rated for 125volts. Does that mean I can't use it? I found a few phone numbers for places that sell these fuses through the website you provided - I'll call them tomorrow.

THANKS!!!!!!!!

[BobND]

Nothing wrong with using a fuse of higher VOLTAGE rating.

[DennisG01]

Good to know, thanks. I know that when it comes to amps, you don't want to go higher, just wasn't sure about volts. I called a couple of those phone numbers from the "little fuses" link. Most only sell them in reels of 1,000. However, I got a real nice woman on the phone at "Fuses Unlimited" and she said she'd send me one as a sample.

I'll let you all know how it works out after I get the fuse in the mail. THANK YOU, GUYS!

[tommac95]

Digikey specializes in small lots (but may have a 5$ surcharge for orders less than $25) . They probably carry LittleFuses. The site can be a challenge to navigate , but a good alternative.

[DennisG01]

Yea, I did look at this site - maybe it was because it was late at night, but I wasn't finding what I was looking for so I went on to the others.