3FE - troubleshooting A/C issue

[1972FJ55]

R12 uses 1/4" male flare ports, occasionally the high-side will be 3/16" flare which was to prevent the hoses being hooked up incorrectly. R134a uses quick-disconnect fittings which are larger and have no threads. Depending on the gauge set, sometimes the R134a fittings unscrew from the hoses and the connection on the hose fits R12 fittings.

 

[alphaeighteen]

R12 uses 1/4" male flare ports, occasionally the high-side will be 3/16" flare which was to prevent the hoses being hooked up incorrectly. R134a uses quick-disconnect fittings which are larger and have no threads. Depending on the gauge set, sometimes the R134a fittings unscrew from the hoses and the connection on the hose fits R12 fittings.

Thanks for that. I have some r12 to r134a adapters on order and hope this will allow me to join up to my manifold gauges to check how much refrigerant is in there. Based on the quality of the hiss it doesn't seem like there's too much in there. One thing that I'm missing is that the 12v is disconnected. Does anyone know where the 12v should be connected to or where the wire should be running from for the A/c?

 

[BILT4ME]

Realize that you should not use a set of R12 gauges on an R134 system or vice-versa. The reason is contamination. The oil in an R12 system does NOT like the oil in an R134 system. It creates lumpy crap that clogs up things.

If you have R12, you stay with R12, OR you replace a bunch of parts, flush the system, and re-charge with new oil and new parts and new freon.
If you have R134, you stay with R134.

Each piece in the system retains a bit of residual oil. That's the reason for the flush.

If your compressor cannot turn (you're not going to turn it by hand, even if it's good) and it's truly locked up, then it's time to convert to R134. That means new compressor, new expansion valve, and new condenser. If it was me, I'd also change to all new hoses since they are 25 years old.

Look on the pump for the lug. Should be 2 wires. One is hot, one is ground. Doesn't really make a difference. As long as there is current to lock the magnetic clutch.

Start engine, apply voltage and ground. If compressor turns, it's good. Probably.

Keep your hands and sweatshirt out to the fan and belts.

 

[alphaeighteen]

Realize that you should not use a set of R12 gauges on an R134 system or vice-versa. The reason is contamination. The oil in an R12 system does NOT like the oil in an R134 system. It creates lumpy crap that clogs up things.

If you have R12, you stay with R12, OR you replace a bunch of parts, flush the system, and re-charge with new oil and new parts and new freon.
If you have R134, you stay with R134.

Each piece in the system retains a bit of residual oil. That's the reason for the flush.

If your compressor cannot turn (you're not going to turn it by hand, even if it's good) and it's truly locked up, then it's time to convert to R134. That means new compressor, new expansion valve, and new condenser. If it was me, I'd also change to all new hoses since they are 25 years old.

Look on the pump for the lug. Should be 2 wires. One is hot, one is ground. Doesn't really make a difference. As long as there is current to lock the magnetic clutch.

Start engine, apply voltage and ground. If compressor turns, it's good. Probably.

Keep your hands and sweatshirt out to the fan and belts.

Thanks for the advice - so I should have two sets of manifold gauges? The ones I bought are new so if i'm keeping the R12 it should be ok? I'm most likely going to convert to r134a though if the compressor is bad.

The compressor that I got new is for r134a. I noticed that the pulley and clutch turn freely on this new one that I got and the one on the car does not?

I'll try to start the car and apply the voltage to see if the compressor turns by hand, If i understand this correctly that once the clutch is engaged I should be able to turn the pulley too? ( there is no belt on the a/c currently. I've got new belts on order to replace them). I'm also still wondering where the actual 12V line for the a/c switch is since I don't see it anywhere inside the engine bay.

 

[BILT4ME]

Thanks for the advice - so I should have two sets of manifold gauges? The ones I bought are new so if i'm keeping the R12 it should be ok? I'm most likely going to convert to r134a though if the compressor is bad.

The compressor that I got new is for r134a. I noticed that the pulley and clutch turn freely on this new one that I got and the one on the car does not?

I'll try to start the car and apply the voltage to see if the compressor turns by hand, If i understand this correctly that once the clutch is engaged I should be able to turn the pulley too? ( there is no belt on the a/c currently. I've got new belts on order to replace them). I'm also still wondering where the actual 12V line for the a/c switch is since I don't see it anywhere inside the engine bay.

I'm not doing a good job of explaining this.


First, the reason you can turn the one on the bench is because there is no pressure in the system.

The connectors on a set of R12 gauges are DIFFERENT from R134 gauges. If not, they SHOULD be.

If you CONVERT a set of GAUGES, you also need to flush freon through them so you don't contaminate your system with the opposite oil.

What I'm really saying is don;t bother hooking up gauges to the system yet.

Locate the plug. Rig a set of wires to the plug that you can touch one side to the positive terminal and the other side to the negative terminal. If the clutch engages and the compressor turns, it is PROBABLY good and just needs a recharge.

However, that also means the system is probably low on charge with R12. You're not going to run down to the local FLAPS (Friendly Local Auto Parts Store) and pick up a couple cans of R12. You MIGHT find some on CraigsList for about $30 per can. Then you would have to put in some freon.

If you already have a new compressor, then you have already started the rework and it's not really worth re-doing the system in R12 strictly due to cost.

Then you convert to R134 for a total of less money and better availability.

o you have Factory Service Manual for this truck?

If not, Contact @jonheld to see if he would be so kind to assist with one. You will have to ask nicely. He's kind of a grumpy bear. He is also the foremost authority on the 3FE engines and systems.

There are other guys like @flintknapper that are a whole lot better at 'splainin' the AC system and what you should be doing.

 

[alphaeighteen]

I'm not doing a good job of explaining this.


First, the reason you can turn the one on the bench is because there is no pressure in the system.

The connectors on a set of R12 gauges are DIFFERENT from R134 gauges. If not, they SHOULD be.

If you CONVERT a set of GAUGES, you also need to flush freon through them so you don't contaminate your system with the opposite oil.

What I'm really saying is don;t bother hooking up gauges to the system yet.

Locate the plug. Rig a set of wires to the plug that you can touch one side to the positive terminal and the other side to the negative terminal. If the clutch engages and the compressor turns, it is PROBABLY good and just needs a recharge.

However, that also means the system is probably low on charge with R12. You're not going to run down to the local FLAPS (Friendly Local Auto Parts Store) and pick up a couple cans of R12. You MIGHT find some on CraigsList for about $30 per can. Then you would have to put in some freon.

If you already have a new compressor, then you have already started the rework and it's not really worth re-doing the system in R12 strictly due to cost.

Then you convert to R134 for a total of less money and better availability.

o you have Factory Service Manual for this truck?

If not, Contact @jonheld to see if he would be so kind to assist with one. You will have to ask nicely. He's kind of a grumpy bear. He is also the foremost authority on the 3FE engines and systems.

There are other guys like @flintknapper that are a whole lot better at 'splainin' the AC system and what you should be doing.

Cool, yes this makes a lot more sense. I have a FSM.
I did just get a compressor but I was also thinking that I could just drop in some of this for R12 Home if everything is working well?
The compressor specifically states that it's for R134a, I'm assuming that all compressors now adays would only be produced for r134a anyways.

 

[1972FJ55]

Cool, yes this makes a lot more sense. I have a FSM.
I did just get a compressor but I was also thinking that I could just drop in some of this for R12 Home if everything is working well?
The compressor specifically states that it's for R134a, I'm assuming that all compressors now adays would only be produced for r134a anyways.

Most compressors for the 80 series come with oil for R134a. The only difference in the R12 and R134a compressors is the oil. R134a systems use PAG46 and R12 systems use mineral oil. You can drain the PAG oil out of the compressor and instill mineral oil if you want to remain R12. Usually when we see an unplugged compressor, it's because it's locked up. If indeed it is, this is the time to go through the whole system. Basically replace the compressor, drier, expansion valve and all the O-rings. You may find the evaporator has a bunch of debris on it when you remove the evaporator box and you can often just clean and re-use.

 

[alphaeighteen]

Most compressors for the 80 series come with oil for R134a. The only difference in the R12 and R134a compressors is the oil. R134a systems use PAG46 and R12 systems use mineral oil. You can drain the PAG oil out of the compressor and instill mineral oil if you want to remain R12. Usually when we see an unplugged compressor, it's because it's locked up. If indeed it is, this is the time to go through the whole system. Basically replace the compressor, drier, expansion valve and all the O-rings. You may find the evaporator has a bunch of debris on it when you remove the evaporator box and you can often just clean and re-use.

Cool, I'll test this out first to see what happens (I'm assuming it's locked up and I've already got all the new parts on order), but just curious to see). Been doing a lot of research and it looks like the expansion valve will be the hardest part to pull since it's inside the passenger side of the system and i'd have to pull the whole evap box to get at it.

Also, would you happen to know where the 12V line should connect to on the A/C system? It's just pulled and I don't see a connection as to where it should be linked up to.

 

[1972FJ55]

Here's a great thread on evaporator removal:
A/C system - how to remove the cooling unit, evaporator, expansion valve
The wire from the vehicle goes from the passenger side inner fender to the oil pressure sender and the A/C connector.

 

[alphaeighteen]

Here's a great thread on evaporator removal:
A/C system - how to remove the cooling unit, evaporator, expansion valve
The wire from the vehicle goes from the passenger side inner fender to the oil pressure sender and the A/C connector.

Awesome, thanks!!

 

[alphaeighteen]

Here's a great thread on evaporator removal:
A/C system - how to remove the cooling unit, evaporator, expansion valve
The wire from the vehicle goes from the passenger side inner fender to the oil pressure sender and the A/C connector.

Stuck the 12v and bridged the gap with a multimeter since that's the only way I knew how to quickly? I'm assuming this would work to provide power to the compressor. Nothing happened and I still can't find the 12v power thats supposed to be coming from the passenger side. I've attached a picture of what I see coming out of that side.

I'm assuming this means I should do some replacing but that's ok since I have the parts. I will likely do the full r12 to r134a conversion.

 

[alphaeighteen]

I was trying to trace the pressure switch 12v without much luck on the driver's side. However I did find some randomly disconnected items and looped off wires .....

 

[Rush]

The 12v to power the AC clutch is the last plug on the passenger side wire harness, it's after the oil pressure sender.

I hesitate to even suggest this, but you seem responsible and cautious enough to not do this recklessly.
If the connector is AWOL/hosed, (or there's no freon and therefore the low pressure switch isn't closing) you caaaaaaaan circumvent the safety mechanisms for diagnostic purposes. Jump the plug on the compressor to battery positive terminal for a SHORT moment ONLY to check tire clutch functions/engages with voltage. I did this to confirm mine worked, for a few seconds at a time. First see if it clicks with the motor stopped, then test it with the motor running.

The usual precautions apply, as you'll likely kill the compressor in short order if you run it like this for longer than a few seconds.

 

[alphaeighteen]

The 12v to power the AC clutch is the last plug on the passenger side wire harness, it's after the oil pressure sender.

I hesitate to even suggest this, but you seem responsible and cautious enough to not do this recklessly.
If the connector is AWOL/hosed, (or there's no freon and therefore the low pressure switch isn't closing) you caaaaaaaan circumvent the safety mechanisms for diagnostic purposes. Jump the plug on the compressor to battery positive terminal for a SHORT moment ONLY to check tire clutch functions/engages with voltage. I did this to confirm mine worked, for a few seconds at a time. First see if it clicks with the motor stopped, then test it with the motor running.

The usual precautions apply, as you'll likely kill the compressor in short order if you run it like this for longer than a few seconds.

I tried jumping it with a multimeter. I can see that there is voltage but nothing happens. I think I can assume that it's dead now :/

 

[Rush]

I tried jumping it with a multimeter. I can see that there is voltage but nothing happens. I think I can assume that it's dead now :/

I'm not sure a multimeter will pass voltage, so try with a wire.

But, that said... No click at all when voltage is applied?

 

[alphaeighteen]

I'm not sure a multimeter will pass voltage, so try with a wire.

But, that said... No click at all when voltage is applied?

No click - I'll try a wire next. Didn't have one handy in the garage and the closest thing was the multimeter

 

[jonheld]

Stuck the 12v and bridged the gap with a multimeter since that's the only way I knew how to quickly?

Uhhh...no. Please don't do this.
If the meter was set to amperage and the probes were plugged in correctly, this could work, but meters are fuse protected and usually have a low current rating. This would not work at all on the voltage setting. Imagine the light show while measuring voltage across battery terminals.

 

[alphaeighteen]

The 12v to power the AC clutch is the last plug on the passenger side wire harness, it's after the oil pressure sender.

I hesitate to even suggest this, but you seem responsible and cautious enough to not do this recklessly.
If the connector is AWOL/hosed, (or there's no freon and therefore the low pressure switch isn't closing) you caaaaaaaan circumvent the safety mechanisms for diagnostic purposes. Jump the plug on the compressor to battery positive terminal for a SHORT moment ONLY to check tire clutch functions/engages with voltage. I did this to confirm mine worked, for a few seconds at a time. First see if it clicks with the motor stopped, then test it with the motor running.

The usual precautions apply, as you'll likely kill the compressor in short order if you run it like this for longer than a few seconds.

Ok, so I did this with a wire and I can see the clutch visibly move in and out as the voltage is applied. I guess my next step is to try putting a belt back on and starting it up? I have belts readily available( got some cheap ones to test it).

 

[Rush]

Ok, so I did this with a wire and I can see the clutch visibly move in and out as the voltage is applied. I guess my next step is to try putting a belt back on and starting it up? I have belts readily available( got some cheap ones to test it).

I'd try turning it by hand or with a rachet/socket while engaged.
If it doesn't turn, you have your diagnosis.
Is it does, then maybe it's not totally hosed.

 

[alphaeighteen]

I'd try turning it by hand or with a rachet/socket while engaged.
If it doesn't turn, you have your diagnosis.
Is it does, then maybe it's not totally hosed.

Good call. Nope the pulley is locked up and the clutch was spinning on the pulley even when engaged. I will start the process of replacing this and the other parts