I am wondering how I can diagnose my fan clutch. Temp seems to climb a tad at idle and once I get going it seems to go down to op temp(190ish). Also when I come to an idle my Ac doesn't blow NEARLY as cold as when I'm moving (freeway or just in town). I know for obvious reasons on the free way it is going to naturally blow colder but even in city it blows really cold just not at idle.

Was thinking of adding an aux pusher fan for the condenser but thought I should look at the process of diagnosing my fan clutch first. Thanks all

 

With the truck warm cut the engine off, try to spin the fan..it should have quite a bit of resistance. If it spins pretty easy/almost no resistance then it's bad.

But a good fan clutch. I've had too many cheap ones to count. One thing you really can't spend too much money on. If you find a good reputable one you want, shop around online to possibly save a few dollars

Probably wouldn't hurt to spray out your radiator and ac condenser. Water hose works fine a pressure washer can bend the fins.

Symptoms definitely sounds like a fan clutch issue

 

A year ago I flushed out my hoses and condenser when I replaced my accumulator orifice tube all the seals and converted to 134. Ac blows Ice once I get going and warm when I come to an idle. Ac fan you are referring to is fan clutch just to be sure we are on the same page.

Also do you know of a good fan clutch. I work at O'Reilly and we carry Murray products and I can get one for 80$

 

I test them 2 ways cold with feeling amount of air being delivered and warm with a 2x4. When it's cold and you first start it up is the fan blowing good? Then when it's warm take a 2x4 and lightly try to stop it. If it stops to easy it's shot.

My fan was bad cold. I had no air behind it and I could stop it with my hand but warm it would lock up. I ran a Murray for my replacement

 

I will check tomorrow morning when the engine is cold

 

Yes I was talking about the fan clutch. The Murray will probably be fine, personally I like their products but the last fan clutch I bought for an idi was five years ago and around $200
Was a extra heavy duty or something

 

R134 is nowhere near as efficient as R12. The condenser on R134 systems is much larger than condensers on R12 due to the inefficiency of R134. When you convert a R12 system to R134 and don't change the condenser you get exactly what you're seeing. The fan doesn't pull near enough air across the condenser to extract the heat from the compressed R134 so the system blows lukewarm air until you get moving again.

 

He is right on point with this, what your systems charged at May have something to do with this. I always charge mine to blow nice and cold at idle so traffic/sitting there talking it's survivable. Most retro conversions I do I overcharge them slightly, maybe you have too much? Weak compressor may have something to do with it too. When there weak they don't pull down/pump up as good as there supposed to.

I would definitely change the fan clutch if it's bad and go from there. Let me know how that Murray clutch works out for you

 

Very Interesting Comments by you and DarkOverCast. THANKS!

My truck is originally from California and the conversion to R134 was done long before I bought the truck. How can I tell the difference between the R12 and R134 condenser coils? The one I have appears to take up almost the entire available space.

A/C wasn't working when I bought it and I noticed that the compressor had been leaking in the past (dried and caked-on oil) so I removed the belt and disconnected the electrical connection for the compressor clutch. I don't remember if the clutch worked but I know that I'll at least need to rebuild or replace the compressor but the rest of the visible system components still look good. I'll need to fix this in the next 6 months because I'll be moving to a hot climate zone.

I would certainly prefer to have the R134 condenser coil - Just wondering if the one I have now is for R134 or R12 and how I can tell the difference.

THANK YOU.

 

If the current condenser takes up all of the space in front of the radiator then there isn't much else you can do. Just don't get stuck in bumper-to-bumper traffic.

 

I believe that this is my problem rather than the fan clutch. Do you have a part number for a r134a condenser or which truck would get one off of/for?

I'm pretty sure my condenser is for r12

 

I'm almost positive you have the r12 condenser because the 134 is not a direct swap unless you buy another evap core or line. Adapters are hard to find these days

Same thing for you. The condenser will bolt in but you'll have to trim it, bend the lines, build/buy a line adapter or evap and hose.

 

What is the process of putting a 134 condenser in my truck? New everything pretty much?....

 

You're lucky because these guys can't be too far away from you and retrofitting modern AC systems into old vehicles is exactly what they do for a living.

Vintage Air - Inventors of Performance Air Conditioning - www.vintageair.com

http://www.vintageair.com/contact.asp

 

before worrying about the AC operation, deal with the fan clutch. my bet is once it is working properly, the AC issue will go away.
the big hint here is the fact the truck starts running hot when at idle or at low RPM's in traffic. this is a sure sign of bad fan clutch or low coolant level. but since the AC also suffers at low RPM's, that pretty much rules out low coolant.