76 454 r134, No Cold Air

[alfreema]

My AC fan became intermittent and then ultimately stopped doing anything several years ago so I stopped using the AC system and anything else that required the fan.

Today I decided to read several threads on this site, and it turned out the purple wire to the blow motor was just baaaarely connected and the exposed portion of the spade terminal was tarnished.  So I sanded that a bit and then tightened up the "kinda" loose ground wire, and BAM, now the blower motor is running again and the fan motor switch works in all four positions.

But now I have no cold air.   

I agreed to have a tech convert my system from r12 to r134 many years ago, but I am AC stupid other than what I read on this site.  Is there a thread on here that gives a high-level overview of the sequence of troubleshooting an AC system in a square body?

Now that I know the blower motor is working fine, what would be the next thing to check and how do I check it?

Thanks for all your help!

[alfreema]

Update:  I just went out and watched the engine with the fan set to HI with Max AC.  The clutch clicks on and spins for about 15 seconds then clicks off and does nothing for 15 seconds, then clicks back on for 15 and so on. I have no idea if that's normal or helpful in troubleshooting, but thought I would add that observation.

[Rapid Roy]

I have seen AC compressors do a similar operation. I found out it was a low freon condition. May be your symptom. May need to check that.

[alfreema]

Yeah, that actually makes a lot of sense, since it's been a long time since I have used it.   How frequently should an AC system's refrigerant be replaced vs just topped off?   What kind of ball park quote should I expect in 2024 to replace it vs top it off?   And how do I know I am taking it to someone that's actually good at AC system stuff (or is it so easy that any reputable shop should be able to handle r134a easily)?

[Rapid Roy]

Probably do not need to replace refrigerant unless there is a failure somewhere in the system. Normally do not need to add more freon unless it is not cooling very well which means there could be a leak in the system somewhere. Prices will vary from shop to shop and how much freon is needed. Depending on your area, most repair shops are equipped with techs that are certified. Could be a shop you usually use or someone that can recommend one.

[alfreema]

Okay that helps.   I will call around on Monday and find a shop to top off the system.

[Rapid Roy]

Have you resolved your AC issue?

[JohnnyPopper]

If you haven't already fixed this, it's pretty easy to do yourself.

First, the fact that the clutch engages suggests that you still have freon.

Buy a can of r134 that has a gauge and act according to the instructions.

Having A/C is one of life's little perks in these old trucks.