In my 1990 F350 truck the AC isn't currently working because the schrader valve on the low side leaked out all the refrigerant a couple of years ago.
Does anyone know how many 12 oz cans these trucks take? My truck has the 7.5L engine.

Would I need to change out the receiver dryer as well as the orifice tube?

 

3 lbs, or 48 ounces of R-12

 

Is that the same for r-134a?

 

no idea, i do not use 134A in R-12 systems. i put in what the system was designed for.

 

For 134, you'll want to use 80-90% of the R12 amount.

 

Personally I would not downgrade to an inferior refrigerant. But if you feel the need to do so the Ford manual states 33 oz. of R14a for a 1995 F series truck (factory R134a).

You will also need a red orifice tubes versus the blue one that should be in there for a R12 system.

I highly suggest you change the receiver/drier to on suitable for R134a.

Be aware the hoses on your 1990 do not have liners in them. The smaller R134a molecules will permeate the hoses much faster, meaning leak out. Add in 20+ years of service they are already leakers, R134a will make the problem worse.

 

agreed. that is the main reason why i do not convert. plus the R-12 just cools better. my truck blow sub 40 degrees out of the dash outlets. i have never seen a conversion cool any better than 55 degrees from the outlets..

 

Yea good idea to replace the drier at the very least, they can be the cause of a poorly functioning system because they get clogged up.

134 may be inferior, but a properly functioning system will still freeze you out.

 

May as well overhaul the whole system and get all 134a parts, it's not that expensive and it will keep you cool for a long time

 

In all honesty you will find thousands of threads on this topic. Some have no issues with a cheap and dirty conversion, others not so much. My theory is if you plan to keep the truck, rebuild the A/C system the right way.

Personally I still would not do a R134a conversion. New hoses, yes. New condenser? probably not because the older systems are not as prone to clogging up with no way to clean them as the more efficient parallel flow version on later models. New receiver/drier, orifice tube, compressor, lines and a thorough flush...good to go.

I do my own A/C work and have made my fair share of bad decisions based on money and learning curve. Your mileage may vary.

 

Ford had a TSB where the OBS R134a capacity was raised up to 38oz

 

Ok, so I was able to verify that the system does not leak with the gauges and I put 36 ounces of 134a in which is 75% of what you guys recommended for r-12.

The compressor comes on and the air output is cold. Is that ok that I only put in 75% or is that too low and will that create any problems?

 

Anyone know about diagnosing a turn signal problem on this truck?
They're not blinking (none of them)
When you turn the signal just stays solid lit.
The hazard signals however work properly.

 

sounds like a bad flasher. it will either be in the fuse panel, or on the back of the fuse panel. don't remember where exactly on the 90.

 

Anyone know how to remove the rear door lock actuator on the 1990 F350?