Upgrading 1987 R10 A/C to R134a parts / questions

[TX87R10]

Hey everyone. I have a 1987 R10 with a 305 that I just picked up and am looking to diagnose the A/C issues and upgrade what is needed. I verified that the fitting on it is still R12. The A/C nor heat blows at the moment but after reading some threads on here my plan is to -

1. Open the system up and check for black death
2. Assuming it's somewhat clean, flush the lines
3. Replace the compressor
4. Replace the fittings with R134a fittings
5. Try to recharge the system with R134a
6. Fix the floppy vents with some velcro

I had a question on parts though -

What else should I specifically change? I see a lot of mentions about the lines converting to blue lines so I'm assuming the factory lines aren't great to keep around. It would be awesome if I could keep the A/C rebuild around $500 if possible and I'd rather do it all at once if I can get it near there.

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[TX87R10]

Also FWIW I tried to do a search on the forums for previous threads but ended up just getting all of the recent posts not really narrowed down to R10 so apologies if this has been asked 100 times.

 

[1987 GMC Jimmy]

Most people will just lump the R/Vs in with the C/Ks, but it’s good that you use the right nomenclature. Lines are fine if you’re keeping the R4 style. You need to get the new service ports in the conversion kit they sell, Ford blue orifice tube, accumulator, compressor, a small bottle of PAG 150, new refrigerant, and flush the lines/evaporator/condenser. Make sure you pull vacuum for a while to make sure it’s holding it and all the moisture is evacuated. Should be 27-29” and holding. Should be about 80-85% of R12 charge. Cite the Harrison sticker on the evaporator case and just do the math on it.

 

[Craig 85]

Change all the O-rings in the system to the green ones designed for R-134 and lube them with the PAG oil when installing.

 

[Bextreme04]

Check the pressure in the lines first. If there is still pressurized R-12 in there, i'd spend my time figuring out why it doesn't blow and save the complete system rebuild for when you actually develop a leak. I have a 1993 Honda civic I use as a commuter and it has R-12. I have all the components to convert it to R134 when the system finally dumps on me, but it works pretty good right now, so I just have the parts on standby and run it like it is.

 

[Vbb199]

Costed me under 100$ to convert my suburban w/ front and rear AC to R134a, and charge it.

New o rings,
Orifice,
PAG oil,
134a freon
Adapters to go from R12 to R134a.
New air dryer.

R12 and mineral oil purge I did here at home.

Drawing the vacuum and charging it... Also did it at home.


Like @Bextreme04 said, you should see if your R12 is still pressurized.

You said neither heat or AC blow out the vents.

That could be control OR blower motor and its resistor related.
Not necessary to take the AC system apart yet until you deduce you've lost your vacuum on the AC system.

 

[1987 GMC Jimmy]

It sounded to me like the heater core may have been bypassed, and then the a/c doesn’t work. I guess that part warrants clarification. Makes sense to check the R12 pressure to make sure it’s empty, but if it sat for any protracted periods during it’s life, which it does like it’s been garaged, I will bet you that it puked the charge around the edge of the shell.

 

[TX87R10]

Thanks for all the replies, I went by AutoZone but they didn't have a set of r12 gauges. Besides pressing the nozzle is there any other way to check if it is pressurized? Trying to find the best way to troubleshoot. I'm guessing to upgrade the process is to drain it using the nozzle method before flushing?

I'm guessing there is no pressure because the guy I bought it from mentioned it hasn't worked in years. It will be good to go through everything though to get more familiar with the system so thanks for all the tips.

 

[1987 GMC Jimmy]

If someone had the foresight to put leak dye in it, and you have a UV light, you could check the service ports, all the different connections around the condenser, accumulator, and evaporator and around the compressor manifold, shell perimeter, and around the back of the clutch to see if you can see where it leaked. It would have done so years ago so that might be hard to see. I will say that just hitting that valve core to see if stuff comes out isn’t a good idea if it’s still an R12 system. Not from the save the whale angle but more so from the R12 is expensive angle.

 

[TX87R10]

Well I pushed a key on the nozzle just a touch and heard some pressure so that's a good sign. Diagnosing the blower motor now thanks for the insight.

 

[TX87R10]

So finally figured out how to use a multimeter properly again and was able to trace power. I took off the dash bezel and checked at the controls but I guess I couldn't find a proper ground because I couldn't get a reading there at all. Went to the resistor and relay and found power in to both, made sure A/C was on at hi and that power went in to the relay and checked the purple wire out to the blower and it had 12 volts but blower does nothing.

Looks like I can replace the blower motor for ~$30 and see what happens after that.

As a note when I turn the A/C on or off I hear a slight hissing sound in the cabin so hopefully that is a good sign.

The clutch on the compressor does not appear to engage but I'll check that once it's moving some air. Thanks again for everyones help!

 

[Bextreme04]

So finally figured out how to use a multimeter properly again and was able to trace power. I took off the dash bezel and checked at the controls but I guess I couldn't find a proper ground because I couldn't get a reading there at all. Went to the resistor and relay and found power in to both, made sure A/C was on at hi and that power went in to the relay and checked the purple wire out to the blower and it had 12 volts but blower does nothing.

Looks like I can replace the blower motor for ~$30 and see what happens after that.

As a note when I turn the A/C on or off I hear a slight hissing sound in the cabin so hopefully that is a good sign.

The clutch on the compressor does not appear to engage but I'll check that once it's moving some air. Thanks again for everyones help!

Chances are, you will need to trace a string of issues. Make sure when you are testing voltage through a circuit, that you are using the ground that is being used by that circuit. The ground is just as important to the circuit functioning as the power feed. If you test to the ground being used and don't have voltage and then test to battery ground and have voltage, you need to remove and clean the ground for that circuit.

The compressor clutch should be engaging regardless of the blower motor. It will have a low pressure switch(or a trinary switch) in the circuit to keep the compressor from engaging when there is not enough(also too much in the case of a trinary) pressure in the lines. That circuit is very simple and should only have a relay and the low pressure switch in between the controls and the compressor. If you are hearing sucking or whooshing sounds when you move the controls, you likely have vacuum leaks in the AC controls under the dash. You might need to remove the whole box under the dash and go through all of the controls, vacuum lines, and doors to make sure they are functional.

 

[TX87R10]

Chances are, you will need to trace a string of issues. Make sure when you are testing voltage through a circuit, that you are using the ground that is being used by that circuit. The ground is just as important to the circuit functioning as the power feed. If you test to the ground being used and don't have voltage and then test to battery ground and have voltage, you need to remove and clean the ground for that circuit.

The compressor clutch should be engaging regardless of the blower motor. It will have a low pressure switch(or a trinary switch) in the circuit to keep the compressor from engaging when there is not enough(also too much in the case of a trinary) pressure in the lines. That circuit is very simple and should only have a relay and the low pressure switch in between the controls and the compressor. If you are hearing sucking or whooshing sounds when you move the controls, you likely have vacuum leaks in the AC controls under the dash. You might need to remove the whole box under the dash and go through all of the controls, vacuum lines, and doors to make sure they are functional.

Thanks Bextreme04 - any tips on using a multimeter inside the dash? It looked like the black wire was running back up in to an area that would have been very difficult to attach on to so I think that you nailed the issue for me there. I picked up a set of alligator clips on a lead extension to make it easier in the engine bay but not sure it would be long enough to use in the dash like that.

As far as the box removal to check for vacuum leaks, I'll definitely check that next. Trying to get air blowing and then I'll start going through the A/C (and hope it's not leaking )

 

[Bextreme04]

Thanks Bextreme04 - any tips on using a multimeter inside the dash? It looked like the black wire was running back up in to an area that would have been very difficult to attach on to so I think that you nailed the issue for me there. I picked up a set of alligator clips on a lead extension to make it easier in the engine bay but not sure it would be long enough to use in the dash like that.

As far as the box removal to check for vacuum leaks, I'll definitely check that next. Trying to get air blowing and then I'll start going through the A/C (and hope it's not leaking )

What I meant is that you should check both power and ground at the load(motor, light, clutch, etc...). If you try and connect the ground at the attachment point to the body, you are bypassing the entire wire, connectors, and connection to the body itself that could all have issues.

There are a million ways to do troubleshooting, but i tend to go right to the item not working and backtrack from there. If you check at the load, and it has full voltage on the power wire while using the same ground that the load itself is using, then you know the load is bad. If you don't have voltage at that point I will usually then try and check for continuity(less than 5 ohms) from the ground connection at the load to the battery ground(if I can reach it, otherwise the closest main ground source like body or frame). Then I will check for voltage at the load to a known good ground. It is entirely possible to have a bad ground AND no power. If I have no continuity to ground I will then trace the wire to its ground source and remove, clean, and reinstall the ground. Then check again. If you now have continuity you should then protect the bare metal with either dielectric grease or paint(I usually put a dab of dielectric under the connection and then paint over the top). If there is no power, I will usually check fuses and fusible links first. Then I will turn power off and start checking continuity through the power wire until I find the break.

 

[Craig 85]

Since you hear hissing, here's a vacuum diagram for FI trucks.

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