Engine Cooling Fan failing W/O Setting Code?

[GCroyle]

This is really a thread to try to learn more about my weak AC unit. My main gripe is the AC performance when you are stop and go driving, it warms up quick. As soon as you get some draft across the front end from road speed, not too bad. I put a similar thread up last year, this is the new question.



FSM quote "Fan speed is monitored by the ECM. Fan speeds

above or below a calibrated threshold will set a DTC. "



Can you have an under performing electronic viscous fan clutch and not set a code?



I have read in the FSM about the grounding of pin 1 and getting an indication with the factory diagnostic tool about "slippage". Have not tried it yet.



When I am on AIR with engine idling the pressure on the gages goes up, fan modestly kicks in and pressure drops, cycle repeats maybe every 30 seconds or so. Fan does not give you a roar. No overheating problems, but I suspect I'm not working it that hard on a daily basis.



My instinct says fan not fast enough to cool condenser, but book says a slipping fan sets a code. I even tried to watch the fan using an engine timing light and taking the pulse off of a lawn mower engine to trigger the light, don't laugh, it works I was able to see the fan at slip-> rampup -> and slow down, just don't know what RPM I was seeing off course.



Also an observation, doesn't seem to be any real tunnel effect between the CAC and radiator, just a big space with no ducting to contain the air flow across the heat exchanging units.



This is a continuing problem and I have tried lots of expirements to try testing and observing, full gage set, additional air fan for test mode (inconclusive) even spraying a little bit of water on the condensor to watch the gage pressure, that makes it drop. The only relief is keep it moving and run recirculation, hit a stop light and it warms up. Local former Dodge dealership looked at it last year, sorta agreed and shrugged their shoulders.



I know Geno's has a replacement fan clutch unit, just prefer a bit more info before spending.



Thanks guys.

 

[rbattelle]

The simplest test for a slipping fan clutch is to spin a blade by hand. Give it a good whirl, and if it rotates 5 times before coming to rest, the clutch is shot.

That's what the manual says, anyway. My fan rotates <1 revolution when I do this test, so I would suggest the "5 revolutions" rule is really stretching it. 1-2 revolutions max and I'd replace it.

-Ryan

 

[GCroyle]

Ryan,



I tried that, engine cold (cold as it gets here in July) doesn't spin much at all, no noise, no grinding sounds. Is your '03 an electronic viscous fan?



Thanks,

 

[NIsaacs]

Do you think it might be a blend door problem and not the AC? Maybe it is allowing some heat to mix with the AC?? When you are moving, the AC is more efficient and overcomes some heat but can't when not moving?



Nick

 

[GCroyle]

Nick,



No, I have not explored that possibility. When I had it in the shop last summer, IIRC they did the calibration cycle and all was well.



Thanks

 

[NIsaacs]

You might check the vent temps on a cool morning with the engine at normal operating temp. With AC off, just on cool vent, see if the vent air is the same as ambient. Give the system a few minutes to cool off all ducting and test the air temp. If it is more then a few degrees warmer then ambient, I would suspect some heat getting by something. I am not sure just how everything works in all that mess. I would also plug the heater hose at the engine and see if that helps.



Nick

 

[GCroyle]

Nick,



That is a straight forward test, can do. I have the thermometer.



FWIW I recently bought another dedicated AC pocket dial thermometer. Put it in the outlet, it only showed 60 degrees, but air felt strangely colder than 60. This weekend I put all of my various AC and cooking thermometers into ice water and used my best digital cooking thermometer to cross check. The NEW one basically stopped at 60 degrees, no colder. It's going back

 

[mwilson]

Nick,



That is a straight forward test, can do. I have the thermometer.



FWIW I recently bought another dedicated AC pocket dial thermometer. Put it in the outlet, it only showed 60 degrees, but air felt strangely colder than 60. This weekend I put all of my various AC and cooking thermometers into ice water and used my best digital cooking thermometer to cross check. The NEW one basically stopped at 60 degrees, no colder. It's going back

Gary,

I gave up on the pocket ones and now use my Infrared Thermometer. I think that it is far more accurate and you will find that there are colder areas within the vents themselves. When you get the correct angle down the vent it seems like you are getting the actual temperature of the evaporator.



Mike.

 

[GCroyle]

Mike,



I do carry an infrared, agreed great tool. I'll try it.

 

[rbattelle]

Is your '03 an electronic viscous fan?

Yes. Your clutch sounds like it's working. I like NIssacs' suggestion.



-Ryan

 

[GCroyle]

Nick,



Overhead showed 74 about 25 minutes into the morning commute the center vent was about 86, but one additional thought. I'm going to do the test again after leaving the truck outside all night to cool the cab also. My garage holds a lot of heat and this may have been influencing the reading, residual cab heat, unknown but easy enough to try.



Last night driving home 55 mph, about 97 on overhead, on recirc saw mid 40's in center vent so at speed with airflow its not too bad, issue is always stop and go AC performance.

 

[NIsaacs]

Gary,



Thanks for the test, my truck is borderline also so I have been doing some testing too. I have seen numerous complaints on AC performance here, even on new trucks, especially in real hot climates. I have always thought that the newer trucks without a hot water shutoff valve like the older vehicles was partly to blame. Even with perfectly operating blend doors, the close proximity of the hot heater core has to contaminate the cooling core.



My next test is going to be blocking off the hot water line to the heater, maybe just a small c-clamp to squeeze the hose shut.



Nick

 

[sag2]

The only way to really monitor the fan speed is with the scan tool. If the pressures are normal for your ambient and humidity the fan is pulling enough air over the condenser. You need ambient temp, low and high pressures, humidity, and outlet temp. Most little dial thermometers are able to be calibrated by twisting the head on the shaft. Use 32 degree ice water as your test liquid. Once you have the numbers you can determine if the system is operating properly.

 

[GCroyle]

Sag2,



Thanks for the info. The data is not at the level you would need yet, but last evening going home, 98 degrees on OH, high humidity, 55-60 MPH after short run on AC switched to MAX saw 45-50 on center vent, but all of that chages as soon as the truck slows down, hits stop and go, redlight time.



Last weekend with the gages on both pressures would go up, fan is heard to ramp up, pressures come down, fan slows down, pressures go up, fan ramps up, cycle repeats.



Any idea what input the computer is seeing that could trigger the cycling? Or is the fan getting the signal and responding in cycles? I do not see the clutch cycle, just pressure. I also monitored the air inlet temp and air temp to engine via Banks PDA, I did not see any spikes or surges. I think I read that these are additional monitored inputs for the computer to work with.



I actually had an '07 sitting side by side doing repeating this test, '07 fan seemed more vigorous.



I don't think you would accept the performance of this unit if you were sitting in the parking lot waiting for the better 1/2 to pick up something and hurry back.



Nick,



I drove the '97 to work today, VENT temp ran about 5 degrees over OH display temp, truck was out all night.



Thanks guys.

 

[mwilson]

Gary,

My '06 has an anemic A/C system, has been since day 1.



The old '97 I bought has A/C that is far colder, gets so cold that I have to put the air flow to the glass and floor as I can't get my nap in on the way home because the air is too cold out the dash vents,... . :-laf



I am considering adding shut-offs to the heater coolant lines, all the big trucks come from the factory that way. Makes a big difference in cold air performance.



I was eyeballing the lines yesterday trying to come up with something that doesn't require 5 pounds of brass to create. Also can't shut one off as the transmission cooler is teed into it behind the block. Gotta' study it a little more but I am leaning towards one shut-off only plumbed into the return on top of the cylinder head. Just have to make sure that the transmission cooler doesn't loose flow.



Still under study, will post if I figure something simple out.



Mike.

 

[GCroyle]

Mike,



My 1977 Dodge M880 has a manual inline heater control valve. Might want to explore this simple possibility.



Gary

 

[GCroyle]

Update:



Observed warmer duct temp on pass side compared to drivers side, will observe on commute tomorrow. Visited Auto replacement part, blend door fix, Heat, AC replacement parts very interesting, between the other threads on HVAC door breakage and stuff, wow.



Interim test.



IMHO there is a large vertical and horizontal air gap between the radiator and intercooler where the cross brace and top bracket are mounted. I took some duct tape and closed the top attempting to funnel more air ACROSS the CAC and condenser and I wedged two 14" sections of pipe insulation wrap between the outside edge of the radiator and CAC trying to force the air to flow thru the cooling devices rather than pull in thru the large open gaps. I am not blocking any core just directing air. More to follow but initial observations are positive including observing a reduction in temp at the same spot of the condenser while running AC. Noticed a good flow of condensate and a first observation a light coat of frost on the line going to the evaporator core. Also let it run at idle longer than before and heard even more FAN noise.

 

[JFought]

yea i been thinking that the gap is an inefficiency.

The condenser at the front with gaps all the way around. why do i got crap jammed in the fins in the middle of the radiator and none on the inter cooler, but the condenser just gets bugs.

Why isn't there foam, metal, to help the fan draw air directly (almost sealed) through the ac condenser? (like at an idle when thw A/c warms up some. . )

ideas??

 

[GCroyle]

JFought,



I'm just experimenting, no guarantee that I'm not creating a problem elsewhere. I quite satisfied that I have not blocked off any sq. in. of heat exchanging. But if airflow is required to pass thru a heat exchanging device, why not have a somewhat ducted path for the air to be guided thru?



I will have more for better or for worse over the next few days. I have not addressed the major open gap under the truck, but it is a big one. FWIW I took a quick look at my buddy's 2011 Ford 6. 7L, all heat exchanging devices sandwiched w/o major gaps. I have about 3" between the CAC and radiator.