I took my new 2000 D2 up to the shop for a once over, they said the two major problems were that the ignition coil was misfiring (and needed to be replaced) and the A/C compressor isn't working and needs to be replaced.

They were right on about the ignition coil, it was burned like a firecracker. On the A/C compressor, is there a way to diagnose if the whole thing needs to be replaced or if it's just the clutch (or if it just needs to be recharged)? How would they know from an initial once over that the whole thing needs to be swapped out? There is a $400 swing on the cost of parts.

 

Does the compressor even turn on?

If yes, before replacing, I would just vacc test the system and give it a charge. if it holds a charge and does not leak, but does not cool, then could be a bad compressor.

 

Thanks! I'll check this tonight.

 

Re: the ignition coil, I'd imagine that one that was "burned like a firecracker" would not be able to run the truck at all, or at best, it would run terribly. I think that ignition coils usually last pretty long (knock on wood) and most people are able to resolve spark-related misfires by replacing spark plugs and ignition wires, which is an easier procedure that doesn't require removal of the intake manifold (unlike coils). Did you have a flashing check engine light with codes for misfires from specific cylinders? I'd recommend investing in a bluetooth/wifi OBD-II reader and a scanner app for your phone, if you haven't already.

I had a shop tell me I needed a new compressor. There was no refrigerant in the system due to a hole in one of the refrigerant lines.

For the compressor to kick on, it needs the following:
1. Refrigerant in the system at the correct pressure. You can check pressure accurately with manifold gauges, or you can check to see if there's anything in there the redneck way - with a screwdriver to one of the shraeder valves (obviously i don't condone this but if you do, then be careful not to damage the valve, your fingers, or your eyes - stuff is harmful to you and the environment). The screwdriver test will just tell you that there's something in the system - it won't tell you whether there's enough. If you hit the valve and nothing comes out, then there's no refrigerant and that's the first thing you need to address.
2. If there's refrigerant in the system, the systemic pressure is measured by the dual pressure switch, which plugs in right behind the grill in the middle of the truck. Dual pressure switch sends a signal to the ECU saying that pressure is OK (not too high or too low) and that the clutch can engage. You can bypass this temporarily with a wire to close the circuit, to see if the switch is faulty. Pressure switch info here. Testing procedure and pictures here.
3. If the AC is turned on on the head unit (e.g. it's not on ECON mode), then the ECU will send a signal to the clutch to engage if AC is required (cabin temp is hot, outside temp is hot). You can check the climate control ECU for faults with this procedure. Issues here are uncommon.
4. Clutch engages the compressor, which then turns with the accessory belt and moves refrigerant through the system. If the clutch is working, you should be able to see it kick on by watching the pulley. You can test the clutch with the truck off by jumping the pins directly with 12v - you should hear a click, or by seeing if it's getting power while the truck is running with a multimeter.

If the shop tested all of these things, then sure, the compressor is probably the culprit. If they didn't do the full diagnosis, I'd guess that, in order of likelihood, either refrigerant is low/missing due to a leak or there's an electrical issue with the clutch/pressure switch.

Hope this helps. Let me know if you have questions.

 

9/10 shops will not replace a clutch on an AC compressor. Why would I as a shop gamble on a bad clutch, replace it, and then have a compressor that is weak and doesnt generate correct pressures, or starts leaking a year later? Also compressor clutches are a pain to replace.

If the clutch is bad, replace the whole thing. Its near 20 years old

 

Replacing the clutch on a Disco is a 30 minute job.. If the compressor won't come on it is because of one of the following reasons:

1. Bad low pressure switch This can be checked iwth gauges on the system.
2. Actual low pressure in the system - usually due to a leak. Most common leak point is compressor seal. Same pressure check.
3. Bad compressor clutch - can be tested using a ohm meter or jumper across relay

If the pressure is low due to leak, charge the system and look for leaks via dye/soap bubbles/electronic leak detector.

 

Another common leak point is the line that runs from the joint on the drivers side through the body by the grill to the receiver/dryer. When it runs through the front of the body on the left side of the car near the horn, there's a steel clip holding it in place that rusts and causes the aluminum refrigerant line to corrode and leak.

 

Thanks!

I haven’t gotten a meter to test the switch yet, but can confirm there is pressure (still need gauges to see how much) and that the clutch does not engage.

It’ll only be 96 today, got plenty of windows to keep the air moving in the mean time. Still need to get some tools to validate the rest! I’ll update the thread when I take the next step.

 

Turns out it was just low on freon. I took the mechanic’s word for it when he said the compressor didn't work. Finally got some gauges from O’Reilly and saw that the pressure was nearly gone. Called the mechanic to ask how he diagnosed the bad compressor, “It is bad, it never turned on!” Now I know to trust this forum more than the local shop.

Charged it and it fired right up. But here’s my next question. I OVER CHARGED IT. Foolishly, I put in 40 ounces because that what O’Reilly said it needed and it got up to 500 PSI and started intermittently spitting freon out of the right side of the compressor where the pipes go in.

I lowered the pressure down to 275 PSI and it’s been going smooth since. I’m learning fast!! But 2 questions-

1. Is that wire supposed to be coming out of there? What is it for? Definitely doesn’t look like an OEM build would route a wire there like that... But I’m still learning.
2. What type of damage should I be on the lookout for from the high pressure situation?

 

Wow, nice to know you were able to recover from the overcharge. I think all the components could be at risk with pressures that high but the main risk would be the seals throughout the system, which is why you saw pressure venting at the compressor fitting. It also looks like that fitting isn't squarely attached but it could just be the photo. I for one am surprised you could get the pressures that high, but I think it speaks to the health of the compressor and its ability to do its job (for now anyway!).