Testing a fan clutch?

[mk378]

It's pointless to try to test the A/C in cool weather.

DoubleWasp points out that the computer senses the high side pressure and uses that as the trigger to clutch the fan up. You need to be watching the pressure with a gauge to be sure that is really happening.

It sounds like from previous tests, that really is happening and the fan isn't clutching up like it should.

If the weather is hot and the fan is really slow, eventually the compressor will start to cycle off/on on excess pressure and cooling in the cab will be diminished. If weather is cool you may get enough condenser cooling from the slow fan to cool the cabin, though pressure will be abnormally high.

If there is an official procedure to test the clutch by hotwiring it to confirm the fan speeds up, that is what should be done.

 

[The motor guy]

Do you think because it was cold out was the reason it wasn't engaging at the shop? I've checked under the hood several times when it was 75 degrees outside and it speeds up and slowed down like it always has. Of course I don't have gauges hooked up though.

 

[The motor guy]

I guess I need to buy some gauges and see what's going on.

 

[Colt45ws]

It should speed up reguardless of exterior temperature if the A/C head pressure is getting up high enough to call for more fan.
And I don't know how these clutches work; is it possible it has slowly degraded and sounds like its locking up but isnt fully locked anymore and you just haven't noticed the gradual deterioration?
Or maybe its not locking everytime and maybe half the time it gets the signal to lock it fails. So you would still hear it coming in occasionally.

 

[The motor guy]

I'm just only using it when the truck is moving fast at the moment, to avoid damage. Is this why the orifice tube was freezing up? The shop claimed it was cause the system was low and a buddy of mine claims that only happens if their is a clogg or their is too much freon.

 

[DoubleWasp]

Your freon is probably too low from the compressor relief valve shooting open at 450. Unregulated, that's exactly what happens.

The Ram diesel condenser is very thin due to so much being packed in one place. Without active air flow, it's ineffective. It being 55 out won't change anything.

I've done some more digging on this issue, and apparently it is quite a bit more complicated. It is rumored that the fan clutch intentionally does not engage to AC head pressures in some trucks in order to protect the "clean idle" function.

I'm going to mess around with both of my 6.7 Rams tomorrow and see if I can figure a way for you to test without some goofy dealer computer or AC gauges.

On my other Ram, I solved this very issue by installing electric fans ahead of the condenser. That was before I knew any better. I'm going to unplug them and see if I can find out once and for all if it's ECM carelessness or just a bad fan clutch.

I'm going to monitor the signal from the AC's pressure switch, and also ground the park lockout solenoid wire in the fan clutch harness both together and independently. That's how you manually trigger the fan.

If it reacts to the ground, but does not react to AC pressure still, I'm going to jump the AC pressure switch. If grounding the clutch wire works and grounding the pressure switch does not, then the ECM will have been caught being ignorant.

 

[The motor guy]

I appreciate that. I'll continue to keep an eye out on this thread.

 

[DoubleWasp]

Rained out today. Will do tomorrow when I get to my warehouse. Rain can't get in there.

 

[The motor guy]

No problem.

 

[DoubleWasp]

Once the engine is warm, it reacts perfectly to AC pressures. Until warmed up, not really. Funny thing is, it seems to be a lot more friendly in hear. Even if the engine is not warmed up, it will roar like a demon in response to AC pressures. Nearly impossible to get it to do in park.

It seems I made the best decision doing electric fans on this truck instead of a fan clutch.

There has to be some really wonky stuff going on where the fan clutch programming is concerned. I don't understand this st all. Starting from dead cold, it appears entirely uninterested in providing assistance to the AC. Once moving in drive or warm, it's alot more friendly.

Think I'm going to dump both can clutches for the "Strictly Diesel" Ford mechanical fan clutch conversion. This is one of the dumbest things I've ever seen, and I'm coming across any tuning options to change it.

 

[DoubleWasp]

Ok, I'm going to re-post, because I noticed I fast typed and ended up with spell check and my own errors that make it hard to make sense of what I wrote, and it's too late to edit:

Once the engine is warm, it reacts perfectly to AC pressures. Until warmed up, not really. Funny thing is, it seems to be a lot more friendly in gear. Even if the engine is not warmed up, it will roar like a demon in response to AC pressures. Nearly impossible to get it to do in park when cold.

It seems I made the best decision doing electric fans on this truck instead of another factory electric fan clutch.

There has to be some really wonky stuff going on where the fan clutch programming is concerned. I don't understand this at all. Starting from dead cold, it appears entirely uninterested in providing assistance to the AC. Once moving in drive or warm, it's alot more friendly.

Think I'm going to dump both can clutches for the "Strictly Diesel" Ford mechanical fan clutch conversion. This is one of the dumbest things I've ever seen, and I'm not coming across any tuning options to change it.

 

[Colt45ws]

I looked that up. Thats a slick conversion. And makes it very easy to trouble shoot when it does start giving issues. Thats a no brainer. I'd do it.