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Old 05-23-2011, 12:30 PM
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Default 80 Series AC amp. circuit board question

OK so let me preface this by saying I am not all that good when it comes to electronics.

I am troubleshooting an A/C problem on the 80 where all blowers and such work, but the Clutch never engages and I never get cold air. the PO had some sort of rigged setup via a switch and battery power direct to the clutch to get it to work. (Someday I'll do a thread on why I am annoyed with the PO).

Anyway, I fixed all his wiring but still no-go. Following the manual and some threads on mud I checked the AC amplifier, mostly cause its easy to get to

For those electrically-savy people, can you take a look at these photos, and tell me if this one connection is bad? And if so, if its fixable or if I need a new board? If its busted I hope its either fixable or I can find one used...looks like even with a Dan price its 150 or so dollars.

Thanks,
Corey

(In two of the pics its in the upper-right, 3rd pick is pretty obvious).





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Old 05-23-2011, 01:31 PM
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That dark gunk is burnt flux residue. Might not be anything and depending on the flux you sometimes don't need to wash it off (Kester 44 for example is not corrosive). Does sorta look like the joints along that side were reworked at some point. Do you have a photo of the top of the board in this location? You can get blobs like that with too much solder, which is not an ideal job but aren't necessarily bad. This is easy to do with plated through hole PWB, but less common with larger pads. Not sure they look obviously bad, though. I don't like the two big blobs, what are those?
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Old 05-23-2011, 01:37 PM
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Thanks Dave. I went out and looked at my high/low pressure cutoff switch and its not even plugged in....so now my guess is the board is ok and the switch is causing the malfunction

Anybody with an 80 have a picture of where the AC cutoff switch ties into the harness? I have nothing plugged in there, but I don't even see a loose plug in the area....Boo to the PO for leaving me such a mess!



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'74 project pig (sold)

Last edited by coax; 05-23-2011 at 01:59 PM. Reason: Boo to the PO for leaving me such a mess!
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Old 05-23-2011, 01:44 PM
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Quote:
Originally Posted by DaveInDenver View Post
Does sorta look like the joints along that side were reworked at some point. Do you have a photo of the top of the board in this location?
Here's a pic of the top of the board....The green circle has the "bad/dark" lookin solder.

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Old 05-23-2011, 04:07 PM
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Ok, so pulled the battery and tray and foudn the pressure switch hiding tucked down under there. Hopefully that will solve the issue; just gotta now get a newer battery that doesn't leak acid
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'74 project pig (sold)
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Old 05-24-2011, 05:38 PM
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Quick update that I got the A/C working! No thanks to the PO on this one. Plugged the ac amplifier board back in, plugged in the high/low pressure cutoff switch, and success!

Dave, I think you were correct that someone had re-soldered something on that board. When I put it back in the mounting location I noticed the plastic was stripped behind the mounting screw. someone probably pulled it out, fixed the board, and then buggered up the mount.

Appreciate the insight!

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'74 project pig (sold)
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Old 05-25-2011, 01:01 AM
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Makes you wonder why the PO unplugged the pressure switch in the first place
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Old 05-25-2011, 07:44 AM
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Quote:
Originally Posted by corsair23 View Post


Makes you wonder why the PO unplugged the pressure switch in the first place

Because that's what PO's do
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Old 05-25-2011, 08:55 AM
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Quote:
Originally Posted by AHorseThief View Post
Because that's what PO's do
Oh indeed, and this PO was at the top of his game. There has been a multitude of crap that was done poorly, overlooked, not done, etc. Everything from using spacers on the ebrake handle cable when one side wasn't connected in the drum to stripping out a screw on the valve cover and then using an english bolt stuffed in there, it has been a never ending game of "figure out what the PO did and fix it right" on this truck.

Quote:
Originally Posted by corsair23 View Post


Makes you wonder why the PO unplugged the pressure switch in the first place
My guess is that he replaced the drivers side headlight and forgot to plug it in. So much crap as if he would have followed the manual (he had one) to troubleshoot the AC, he would have spent 20 min. Instead he decided to splice in a wire directly to the compressor, run it via switch in the cab to the fuse box, and use that to turn on the ac. probably took 2 hours to do the job wrong, and 20 min to do it right.
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'74 project pig (sold)
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