I screwed the pooch, I think. I’m working on a 2006 Int’l 4300. The ac compressor was shot, so I replaced it and the orifice. I evacuated the system, and started filling it, and the compressor never came on again. The computer is not sending the signal to turn the compressor on, I checked with a meter. The pressure slowly climbed up to 100 psi, and still no compressor. Any clues would be greatly appreciated!
There should be a high and low pressure switch. Check the lines in and out of the HVAC box. Low side should close greater than 7 psi or so. High side should open approximately 275psi. You probably also have a thermal switch which opens at 33°F and colder. A lot of folks forget about the thermal. If your comp crapped out, I hope you serviced the drier and flushed the system. Otherwise your new comp is gonna eat all that trashy oil.
Great info thanks! So, assuming I have currently 100psi in that system, both switches should be closed, and that compressor should be on? I played with those switches, and they were both open. I shorted them one at a time to see if a change happened (it didn’t), but I didn’t short them both.
Also, assuming that thermal switch is closed… then the compressor should be on?
Yes, but you stated in original post, that the computer wasn't telling it to turn on? I'm describing basic A/C like red.dot and others where they're not integrated into the computer system. I don't recall navistar being fully integrated at that time, but, it was a long time ago. Considering you mentioned a computer, it may be variably controlling an electro-viscous fan hub. Lots of variables to consider. Lastly, never dead short a sensor lead. Always use a 1 or 2 amp fuse to protect whatever controller your working with.
I think my biggest problem is, I don’t have an electrical diagram for this truck at all. This was supposed to be a simple swap, and something went haywire, and without that diagram, I’m kind of pissing in the wind.
Can you post the last eight of the VIN. I'm pretty sure a 2006 the AC is controlled by the body module.
5H681239 I think you’re right. I just called my local dealer and spoke with one of their wrenches. It looks like it’s controlled by the PCM / body module / computer. I found a wiring diagram that supports that. So, it looks like all I can do for the guy is to make sure all the switches are working and send him to a dealer I don’t have the software to plug in to the rig, and I don’t think I want to buy it for just this one guy. I don’t work on a lot of trucks, I’m mostly off highway / construction stuff.
There are two thermistors/temp sensors near the HVAC unit under the hood. The original ones leaked. Make sure you have the updated ones installed before they charge the system. You have to take them out to see if they are the updated ones. If you PM me your email I can send you the International HVAC manual for your truck.
What caused the compressor to fail? It seems odd to me that you would have a computer problem after replacing the compressor. Back up and think about what you’ve done. How much refrigerant have you added? By the time you have 1-1.5 lbs in the system, the pressure sensors should have enough to send power to the compressor.
I assume age caused the failure. Customer states that the AC has been getting weaker and weaker over time. I pulled a little under 2 lbs of 134 out of there, and that should have been good for 180-200 psi, high side, on a warm day. It was barely pushing 100. When I turned it by hand, it sounded like rocks in a coffee can. Safe to say she’s done. I have about a lb in there now, and the new one is not cycling. I also replaced the orifice. The manual calls the orifice the “clutch cycling orifice”. I find it kinda funny that I replaced the orifice and my clutch doesn’t cycle
How much oil recovered? Was the oil clear or grey? Did you replace with original equipment or "will fit" ? Some clutches require a ground, some are grounded through the case, some are diode suppressed, some are not. That's why I ask. Did you flush the system and replace the dryer? Have you determined if the sensors are switches or transducers?
Some one needs to make a kit to rewire the ac on older trucks so it dosent have to go through a computer . A Trucks ac units will work and keep the driver cool with out a computer. I would hard wire the compressor and let it run for a little while but keep a eye on the presser then after it is cooling hook it back up to the computer.
You could unplug the compressor and power it with jumper wires or a power probe. I vote to add a second pound of juice and see what happens. If it still doesn’t work, I’d work the electrical backwards from the compressor
Average A/C single cab 1.8 to 2 lbs, sleeper cab 3.7 to 4 lbs, just averages.
This one takes about 2 lbs (I can’t remember exactly at this moment). The reason I stopped adding is the low side got up to 100 psi. I didn’t want to add any more. I thought about just jumpering the compressor clutch, but I didn’t know at the time if doing that would booger things up further. I was going to try that today, along with checking for any codes, pulling battery terminals to reset things, and checking electrical. I sent the guy a text on Friday telling him he could either bring it back, or I’d go to him today. No response. So, who knows, maybe I’m done working on this truck after all ill Keep y’all posted of the ensuing drama.
It's simple enough, but you run into problems competing for fan control
The HVAC manual I sent you tells how to get fault codes through the LCD display in the instrument panel. The bottom of page 23. If the fault code ends with an "A" its an active code. Post what you find.
Yessir! I had read on other forums about how to pull those codes, but I didn't have a source of info as to what they meant. I do now I honestly don't know if / what codes he even has at the moment, he hasn't returned my messages, and there was no indication of codes last week. The diagrams also confirmed the AC is controlled by the computer, which was key info. Thanks again for that info, it saved alot of head scratching!