My 78 F150 (351M, 2WD) has this new issue with the a/c compressor vibrating at just above idle. At idle it's smooth, then vibrates going up through about 1000 rpm, smooths out, and does the same thing when coasting down. Local guy who works on my truck said he's seen that on many of these trucks and it's caused by the belt being too long to run without an extra idler arm, and that Ford should've stuck another one in there to keep proper tension on it. A/C's still working fine after a few weeks of running like this, but it just doesn't sound right and it's really annoying driving around town trying to stay out of that rpm range. I'm thinking maybe old bearings or something, I dunno. Anyone else had this problem or have any suggestions...besides driving this truck into the lake and getting a new one?

 

When factory A/C is present, there are two idler pulleys, one fixed (D8OZ8678B), one adjustable (D8OZ8678A).

1973/79 F100/350: These same two idler pulleys were used with all the V8's.

 

My 77 had the same problem with the old York compressor on it. It was annoying as heck. Mine was belt slap. You can easily test it and see if the belt is slapping by lifting the hood and slowly increase the rpm’s and see if the belt starts flapping around. I cured mine by taking the compressor loose and elongating the bolt mounting holes so that I could slide the compressor over to put more of an angle with the belt on the bottom idler. (That is the one that Bill refers to as the fixed idler)

My compressor belt was out of alignment with the pulleys as well. Elongating the holes allowed me to adjust for this as well. Just get under the hood and look straight down the belt and see if all of the pulleys are in alignment with each other. The belt will really slap if not. I had to put a flat washer under one of the idler pulleys to bring it out where it centered on the belt. If this was dealer air then some of the dealers did a really crappy job of setting up the compressor belt alignment. I hope this helps.

 

Thanks for both of your replies. Definitely some belt slapping going on, looked under the hood yesterday w/ it running and it was bouncing all over at idle. Yay a new project.

 

I searched and found this thread from Number Dummy. My problem is that my '79 with a 400 w/factory air has the adjustable pulley but not the fixed pulley on my AC belt. My belt flops and actually twists no matter how tight I adjust it. I don't see where a fixed idler pulley would mount, does anybody have a picture or good description where it would go?

Thanks

 

Mine is a 460 so it will be a little different. I hope this helps. I took several pictures from different views. PM me with your email address if you want the rest of them. Good luck, Gary

 

HIJACK!!!! Hey Gary what brackets did you use for the Sanden compressor?
-Lance

 

I used angle iron and strap iron from an old bed frame. Those bed frames are made from hardened steel and make good project iron, so if you ever see one in a junk pile grab it.

I should have taken pictures of the brackets before I mounted them, but didn’t think to do so. I simply cut two pieces of angle iron the width of the existing York mounting plate and welded the flat stock vertically to the angle iron the exact distance apart to match the mounting holes in the Sanden. I then set the brackets on the mount and estimated the proper height for the Sanden and then cut the upright flat stock to the proper height and drilled the mounting holes. I then mounted the brackets to the Sanden and set the Sanden on the mount and positioned it in the proper position to get the belt into proper alignment. I then marked the angle iron to align with the existing holes in the original York mounting plate, I drilled them out, painted the brackets and mounted the Sanden.

Mounting that Sanden was the best thing I ever did. I had the old dealer air in my truck and the darn thing wouldn’t cool anything. I pulled it all out and bought a cheap underdash unit and installed it along with the Sanden. Now I can start the truck up on a 110-degree day and the vent temp’s are down into the 40’s before I can get out of the driveway. I couldn’t get the old unit below 50 after 30 minutes of running. The only problem now is not being able to turn the darn thing down low enough. Even on low we have to turn the vents toward the floor to keep it from messing up my wife’s hair. Someday I will take pictures of the project and post them in my gallery.

I could draw you a diagram of how I made the brackets and email it to you if you need it.

 

Sorry to keep highjacking, but I'm interested in those brackets too, any chance you can draw up a diagram?

Also what make/model is that "cheap underdash" unit that you got? Thanks. . .

 

Sorry it took so long to get back to you but I have been really sick. I got my under-dash unit from Nostalgic Air (www.nostalgicairparts.com) they have several products available on their website. The one I got was the UD-110 for $150.00. It was the cheapest and simplest, but as I stated earlier the only problem with it is the blower speed. It will still blow you out of the cab on low and you can’t even turn it to high without messing up your hair.


I will try to draw up a diagram of the brackets in the next few days. The doctors have me on some major anti-biotics and they are keeping me really sick. This makes it difficult to get anything done.

 

Ok here is the drawing of the brackets I built. The front and back brackets are identical. I didn’t show the bottom mounting holes because they might be different in your application. Mount the brackets to the compressor and position the compressor into the proper mounting position and then mark the holes to be drilled to match the holes in the original mounting plate. Drill the bottom mounting holes out and bolt that baby down, put on the fan belt and start plumbing. You will find all of the trouble and work worth it. Good luck.

 

I need to make a correction on this old post in case someone pulls this up for information. I incorrectly identified the compressor as a Sanden. It is actually a Seltec TM15HD. I apologize if this caused any inconveniences.

 

Gary, can you please post a picture of your UD-110 unit installed in your cab? I want to go this route, instead of using an in-dash unit, and I want to see how it fits. Thanks. . .

 

Sorry for taking so long to post this, but I just got back into the state to get to the truck.

 

OK thanks!

So it looks like it takes up the entire center area under the dash, which is fine with me, I don't usually have a center passenger anyway. And you said you're pretty happy with the temperature and cooling capacity of this unit? In other words, it can cool down the cab during those 105-deg days?