HJ61 Air Conditioning Short Circuit

[cruisingjapan195]

1987 HJ61 A/C is not working, and suspect a short circuit somewhere.

I recharged the refrigerant, A/C worked like a champ, so suspected low pressure switch was cutting off the compressor.

3 minutes later, A/C compressor kicked off again (fan still blowing) and I checked the fuse and it was blown. Replaced fuse, and it blew in 10 seconds.

For ~experimental purposes~ tossed in a higher fuse (15A) to see if it would run at all, and it blows immediately.

It seems there is a short circuit but I have no idea how to diagnose that beyond randomly poking things with a multimeter. Any advice is appreciated - my access to qualified mechanics where I live is very limited so stuck troubleshooting largely alone.

 

[duncanrm]

If you're confident its not a low gas (again) fault then I would directly drive the compressor with a fused piece of wire - this will localise the fault to the compressor itself or the circuitry involving the A/C Amplifier.

 

[sved]

Yes, AC amplifier circuit or the compressor itself. If the AC is OEM you can also check the VSV ( Idle up valve ) by just disconnecting the connector.

 

[cruisingjapan195]

If you're confident its not a low gas (again) fault then I would directly drive the compressor with a fused piece of wire - this will localise the fault to the compressor itself or the circuitry involving the A/C Amplifier.

Gave up and found a mechanic who diagnosed a the magnetic clutch as the failed component, but claims he can’t find a compressor to put in it.

It’s a 1987 car and the current compressor takes R12, and I’m curious why I can’t just buy an updated R-134a compressor to replace it. What am I missing here? Is there anything else that has to get replaced to do this or something that would makes a more modern compressor incompatible?

 

[sved]

Why a new compressor ? You need a clutch , not a compressor.

 

[dmjay]

Your options are to replace the magnetic clutch yourself as very few AC shops will guarantee the work, or convert the whole system over to R134a.
I just did the conversation and it is not cheap, all new hoses, seals and compressor. Because of it's age, unless you can find someone to rebuild your compressor you have to find one that bolts onto a 12H-T. Good luck with that. I found a Isuzu truck compressor that fits after TONS of research.
If i was doing this again, i would go down the electric compressor path. Cheaper in the end i think. I will look for the part number for my unit for you should you choose to spend the money.

 

[duncanrm]

Gave up and found a mechanic who diagnosed a the magnetic clutch as the failed component, but claims he can’t find a compressor to put in it.

It’s a 1987 car and the current compressor takes R12, and I’m curious why I can’t just buy an updated R-134a compressor to replace it. What am I missing here? Is there anything else that has to get replaced to do this or something that would makes a more modern compressor incompatible?

Unsure on stateside.. but here in Australia the parts aren't that expensive to convert to R134a.. Whilst a 2H, here's some images of my conversion. I'll get a part number for you for the 12HT compressor as its a pad mount compressor.. Its readily available but you'll have to transfer your manifold off the top of your old compressor over to the new one.

HJ60 A/C fitout · Dec 3, 2024 – Feb 19, 2025 📸

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[duncanrm]

Is this a 24V vehicle and would you have a photo of your existing compressor?

 

[cruisingjapan195]

Your options are to replace the magnetic clutch yourself as very few AC shops will guarantee the work, or convert the whole system over to R134a.
I just did the conversation and it is not cheap, all new hoses, seals and compressor. Because of it's age, unless you can find someone to rebuild your compressor you have to find one that bolts onto a 12H-T. Good luck with that. I found a Isuzu truck compressor that fits after TONS of research.
If i was doing this again, i would go down the electric compressor path. Cheaper in the end i think. I will look for the part number for my unit for you should you choose to spend the money.

I found a compressor that is the exact same part number and supposedly fits this vehicle. Ordered it, and mechanic claims if I can provide the compressor he can replace. Beyond the hoses and seals mentioned are there other parts I need? I intend to convert the system to R134a, because this new compressor despite being the same part number is R-134a anyway

 

[cruisingjapan195]

Is this a 24V vehicle and would you have a photo of your existing compressor?

24V vehicle yes. See attached.

 

[cruisingjapan195]

Why a new compressor ? You need a clutch , not a compressor.

Is that even possible to replace just the magnetic clutch of this compressor?

 

[dmjay]

It is possible, they are about $30.

 

[duncanrm]

I cant help with a 24V compressor part number.. but if worst comes to worst, use a 12V compressor and use the signal wire from your 24V system to drive a relay to switch 12V.. you'll need to come up with a 12V source yourself (centre tap the two batteries at worst, but there's far better options).

The 12V OEX Compressor you'd need is CXD0085 - R134a conversion of course.. so you have other downstream consequences if you go this route.

The 24V Clutch Assembly is discontinued, the part number was 88410-60070

 

[dmjay]

You said you had all the answers Duncan.
The OEX part number is CXD0087.
It is 24v for a Isuzu truck. Bolts on to a 12H-T and lines up perfectly, same belt and all.
You must get new hoses as well. The molecules of R134a are a lot smaller that R12. They will evaporate through the hose in a matter of months. Any good A/C shop will make them for you. I paid $2.5K for everything. Super cold A/C now.

 

[duncanrm]

You said you had all the answers Duncan.
The OEX part number is CXD0087.
It is 24v for a Isuzu truck. Bolts on to a 12H-T and lines up perfectly, same belt and all.
You must get new hoses as well. The molecules of R134a are a lot smaller that R12. They will evaporate through the hose in a matter of months. Any good A/C shop will make them for you. I paid $2.5K for everything. Super cold A/C now.

Nice, I'll add that part number to my list.. I never said I had all the answers, but I now have one more for next time!

@cruisingjapan195 .. it appears the actual Denso compressor is in fact still available from OEX at least (CXD6222) if you didn't want to go Chinese