steeler

Well I found the problem. Pin 16 on the control panel is a ground, I was getting just enough of a ground to operate everything but the compressor. So after running a new ground I have good power to the compressor, but the clutch is toast. Oh well at least it'll be working tomorrow!

10 hours ago, 41chevy said:

Eliminates alot with that info. Does you diagram show the compressor circut tied in with powering the engine fan?

It shows that as separate. It has a separate pressure switch that sends is signal to the ecu for the fan. Didn't have a chance to work on It today, probably in the morning.

8 minutes ago, 41chevy said:

One of the fuse /relay panels has an AC compressor relay that supplies power.  Also the low pressure switch the prevents the compressor from kicking in with less than 50 PSI in the system so I would also put a set of gauges on and check the pressure in the system for starters. 

Should have mentioned that I replaced the condenser due to a leak. I've also tried a new control panel and new temp sensor as well.

I don't have any fuses or relays that are labeled specifically for the compressor. There are a couple others that are marked HVAC, but they are powered and good. 

I did find a different diagram than the one I was using, it's showing power to the compressor coming directly from the control panel, unfused. I'll check for continuity on that circuit in the morning.

2014 GU713, I've got no power to the ac compressor. My wiring diagram is a bit outdated so I'm not sure I'm going in the right direction.

My diagram says fuse 53 is for the compressor, but the sheet in the fuse panel shows 53 as a spare. There was no fuse in it, and three is no power to it, even though it is pinned.

So does anyone know where the power comes from? I know it goes to the pressure switch, I have continuity from switch to compressor, but no power.

Thanks for any help guys.

On 6/25/2019 at 3:35 PM, CCMtruck said:

Update: Just like steeler said. I found aluminum pieces in the inlet side of the ecm cooler plate. Its the simple stuff we forget sometimes.

Good deal. Glad you found the problem!

Did you check the fittings at the ecu cooler plate? They are notorious for catching debris.

Ya this is a tough one without laying hands on it. Sounds like ecu is losing power. Do you have a diagram?

Kinda off topic here but we do quite a bit of work on paccar engines. You wanna talk about an SCR nightmare, wow.

I had one with a def quality fault that just would not clear. I threw everything under the sun at it, nox sensors, def doser, new def fluid, dpf filter, catalyst, 7th injector, countless hours of troubleshooting and test driving all to no avail.

Ended up opening a case with paccar engineers and after several regens and 2 40 mile test drives that had to be recorded and send to them, they simply gave me 24 hour special access to a feature in the software that allowed me to clear the code out.

I mean really? After all that, it was that easy? I wish they'd give me that special button permanently!

The truck worked fine after that for about a year, then the same crap started again. The customer said screw it and had it deleted, and I don't blame em.

Ya I always try the regen first, sometimes it works for me and sometimes not.

The code won't go inactive until it goes thru it's checks with the 5mph derate temporarily removed. Drive it like that for 30 minutes or so and it will either clear out or tell you it's going to derate again.

Ok after going thru it all again, I can disregard that 33 fault code. I was using a pro link and had the vmac1 cartridge in it. I hooked up the laptop and it's actually a 32, for the rpm sensor. I've eliminated the wiring and sensor, so I believe they have the wrong flywheel in it.

I don't know who was working on it before but damn, let's just say he was a hack.

Sad thing is, I'll probably never know what the outcome is. The only reason it's at my shop is because nobody else could figure it out, so the customer is going to pull the flywheel out himself.

16 minutes ago, Mackpro said:

Mack came  out with a conversion kit to replace the  two VMAC 1 ECM’s  with a single VMAC 2 ECM . The wiring harness on the engine remained the same as original. Chances are the one of the original VMAC 1 ECM’s failed and the conversion kits was installed. 

Hmm. Interesting. Ya everything I'm looking at other than the module screams vmac 1. But I checked the vin and it is coming up as vmac2. The pump part number is correct.

I got more info on this truck. I noticed it has a new clutch and flywheel somebody else put in. I'm now suspecting they may have the wrong flywheel and the rpm sensor is not reading it.

The engine will die if I unplug the tem at the pump, but runs the same with the rpm sensor unplugged. That tells me I've got something fishy going on with the rpm sensor. It's supposed to ohm at 200-300, but I've got 180. It's a PAI sensor, I'm going to put a Mack sensor in it and see what happens.

20 minutes ago, Mackpro said:

Here’s the easiest way to tell a VMAC 1 from a 2  on a CH style truck .  A VMAC 1 has the engine harness plug iinto the firewall right above the windshield washer fluid jug on the passenger side of the firewall. On a VMAC 2 truck , there is a block off plate above the windshield washer fluid jug . Also  , the Econ-Vance is a lot longer on a VMAC 2  and the injection pump almost touches the air compressor, and  of course the VMAC 3 is an ETECH  style engine with the heat shielding  over the individual injector pumps 

Thanks pro. I'm not with the truck right now but I do know there is a bulkhead harness going into the firewall on the passenger side. I remember that was how I could always tell a 1 from 2, but I couldn't remember which was which.

So, sounds like a 1, so why does my module have a vmac 2 sticker on it? Didn't the 1s have an fic module?

No, it won't damage anything at all. It's just annoying.

1 minute ago, Ahubbard said:

Yes I will get that feeling when I drive. Almost feels like the spring is too light on the throttle return even though it’s not. I will let my foot of the throttle some and lay back in to correct that sometimes.

When this does it at 1200 it almost is like a horse galloping. Rhythmic and kinda shakes the motor.


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Yup sure sounds like resonant ride. Unfortunately I'm not sure there's much you can do to fix it. We've sent pumps out before, some were better, most weren't. I'll do some digging about that contraption Mack came out with.

Maybe someone else here knows of a fix?

Yes, resonant ride in the pump feels kinda like the fuel rack in the pump is bouncing back and forth, usually right around that rpm. 

I remember it being a big pain in the ass in the early/mid 90s at the dealership I worked at. Sent out many pumps for this problem, but rarely was it ever fixed.

I remember Mack coming out with some kind of contraption that mounted to the front of the pump to fix it, but man its been a long time!

Does yours almost feel like you are bouncing the throttle real fast at that rpm? 

And usually if the engine had a strain on it, you wouldn't feel it. Only happens when there is steady rpm with little to no strain on the engine.

1200 rpm? Sounds like it could be a resonant ride issue with the pump?

Hi all. I've got a ch dump I'm working on that has a coughing/stumble mainly noticeable at idle. I have a 33 fault code. My vmac 1 book shows the 33 as injection pump speed sensor. My vmac 2 book doesn't show a 33 at all.

Now it's been awhile for me since I don't see many of these older trucks anymore. The module in the cab is a vmac 2 module, but the customer has put a different engine in the truck, that's when this issue started. Is it possible that I have the wrong injection pump because of the wrong engine? Would everything plug in the same on 1 vs 2. 

Like I said, I'm big time out of practice on the older vmacs.

Not to derail this thread, but would a guy gain anything by just changing the manifold only?

56 minutes ago, BucketTrucker688 said:

I'm in need of a Mack 73GC27D or PAI ELA-3543 lash adjusters I'd like to do all 6 but am being told mack and Pai both discontinued them. Now what do I do?

We have a lot of old stock, I'll check in the morning, maybe you'll get lucky and we have some. 

11 minutes ago, scammedbyrick said:

I wouldnt do business with Rick Plauman unless you want to get ripped off

Really? I would have never guessed it. Other than going off of your user name! 😜 lol

11 hours ago, fjh said:

Yup seen it happen a few times ! It even happened when it was a not Swedish owned ! How ever these guys can't really afford  need to piss many more people off,small or big! Volvo/ Mack  market share is dropping like a stone!

Yup, Volvo sure has trashed Mack in my opinion. I mean, what's really left that is actually Mack? Transmission I guess, some suspension? They have even managed to screw up the diffs. Sad.

On 6/5/2017 at 3:23 PM, Keffer inc said:

I'm still in Amarillo Tx, Friday they completed the cam, injectors, and dpf. We went for a test drive and it was still missing badly, maybe even worse. At first they were thinking maybe a valve was damaged inside the head. But Saturday a tech decided that it may have been a fault injector that they got. Haven't heard anything yet but I hope that's it. I've been at a hotel for a solid week now.

Glad it was only the injectors!

A couple months ago I did a cam on an mp8 with only 200k. 

On 5/28/2019 at 1:47 PM, Mackpro said:

We would pull the intake manifold off and drop the intake valve down. Then blow air into the injector hole and blow the little pieces out the intake . Saved us form pulling the head off . 

Yup, I shoulda bought a valve spring compressor!