3rd Gen Blend Door issue. Grab a club cause we are beating this dead horse!

[Big_Horn]

This is not a blend door issue.

 

[cerberusiam]

This is not a blend door issue.

That is undetermined at this point until the HVAC box is disassembled. I would hazard a guess pretty much any 13 year old truck has issues with the blend doors, some worse than others. Warmer than normal air on passenger side can very well be a blend door issue.

Blowing all the refrigerant out is a another issue, that will likely require a replacement of all the critical pieces to resolve. Since the HVAC box has to come out to do the evaporator excellent time to do the blend doors, evaporator, and heater core. Good time to install a valve to shut off the heater core flow in the summer.

 

[Big_Horn]

Really doubt that it is a blend door. It is a single zone system. when the AC was recharged everything worked fine. blew the relief valve and back to where I started. Trying to find out why the clutch fan is not turning on, or why the system is spiking. I have read a lot of theories, but nothing of hard fact.

 

[Big_Horn]

oh and @cerberusiam, I'm probably at that point of replacing everything...not happy....

 

[cerberusiam]

I feel your pain. Had to replace the accumulator on mine just to get it to partially work. Still doesn't work right, confirmed blend doors are bad. Will likely have to replace all the parts and flush the rest as pretty sure the accumulator plugged from debris. Justification to buy the recovery system as everything we own now needs AC work to varying degrees.

 

[Tuesdak]

So I had the evac and recharge done today. They said that the system was nearly empty. Recharged, Started the truck and within 1 minute ran the AC on high. Popped the relief valve and dumped the system. He refilled the system and said good luck... kinda back to square one. On my way home I cycled the AC on the freeway after about 5 minutes of engine running and had cold air for about 20 minutes until I turned everything off.

Pretty clear the fan isn't coming on fast enough (or coming on at all) to keep the AC from extreme 450+ PSI excursions. One could ask of the AC shop what the high side was doing before the relief valve popped open (DUH!) I want to be nice, but, the *cough* shop is missing the #1 problem with AC systems and that be an INOP or weak fan. They sent you down the road with a system blowing the relief open with "Good Luck"?! To be fair: Did they suggest any repairs what-so-ever?

I would replace the fan clutch at this point. It's possible the high side AC sensor isn't reporting high pressure to the ECM. A weak fan clutch can keep the engine cool while the AC system burns up at around 190 degrees condenser temp. (190 degrees is around 430 PSIG and the relief opens around 450 PSIG, less than 200 degrees. 200 degrees = 488 PSIG.)

Need justification for the $500 fan clutch part? My experience suggests (as the Fan Clutch wait 15 min OEM test is a joke): Use a hand held optical tachometer or read the FAN RPM with a Smarty Touch or other tech tool. When the AC comes on you should have 1450+ fan RPM at idle before the high side goes over 400 PSIG. Any less RPM like 350 or 650 RPM is overheating the condenser and the head pressure rises till the safety relief vents. For this cost you should verify the AC pressure sensor is working via a scan tool. Gamble on the clutch part if you have an 5+ year old fan clutch.

 

[Big_Horn]

Pretty clear the fan isn't coming on fast enough (or coming on at all) to keep the AC from extreme 450+ PSI excursions. One could ask of the AC shop what the high side was doing before the relief valve popped open (DUH!) I want to be nice, but, the *cough* shop is missing the #1 problem with AC systems and that be an INOP or weak fan. They sent you down the road with a system blowing the relief open with "Good Luck"?! To be fair: Did they suggest any repairs what-so-ever?

I would replace the fan clutch at this point. It's possible the high side AC sensor isn't reporting high pressure to the ECM. A weak fan clutch can keep the engine cool while the AC system burns up at around 190 degrees condenser temp. (190 degrees is around 430 PSIG and the relief opens around 450 PSIG, less than 200 degrees. 200 degrees = 488 PSIG.)

Need justification for the $500 fan clutch part? My experience suggests (as the Fan Clutch wait 15 min OEM test is a joke): Use a hand held optical tachometer or read the FAN RPM with a Smarty Touch or other tech tool. When the AC comes on you should have 1450+ fan RPM at idle before the high side goes over 400 PSIG. Any less RPM like 350 or 650 RPM is overheating the condenser and the head pressure rises till the safety relief vents. For this cost you should verify the AC pressure sensor is working via a scan tool. Gamble on the clutch part if you have an 5+ year old fan clutch.

To be fair, the tech did mention that I needed to replace the clutch fan... without any real discussion why. Ya, the truck is 13 years old on its original clutch, but my question lies, is the Napa replacement worth doing at the ballpark of $250 vs $500. I might as well replace the high side sensor while I'm at it. the system is already pretty low. Condenser is a little rough, some dents from rocks n such. What really throws me for a loop is that prior to having the system recharged, the fan was coming on at weird intervals, only this year. it would stop when I turned off the defrost or AC. I really hate throwing money at the wall and hoping some of it will stick.

 

[Tuesdak]

To be fair, the tech did mention that I needed to replace the clutch fan... without any real discussion why. Ya, the truck is 13 years old on its original clutch, but my question lies, is the Napa replacement worth doing at the ballpark of $250 vs $500. I might as well replace the high side sensor while I'm at it. the system is already pretty low. Condenser is a little rough, some dents from rocks n such. What really throws me for a loop is that prior to having the system recharged, the fan was coming on at weird intervals, only this year. it would stop when I turned off the defrost or AC. I really hate throwing money at the wall and hoping some of it will stick.

Think of it this way: if the blower motor fan quits blowing cold air into the cab you have an AC problem. Same thing if the engine driven fan quits blowing HOT air under the hood from the AC system. Either of the two fans quit = NO COLD AIR. The engine fan is simply forgotten because 45 MPH and delays allow the AC to kinda work without it while system overheat damage gets done. Blowing a safety relief valve from no cooling fan should have been explained better by the shop. Simply put bad fan clutches or burned out electric fans kill the entire AC system. The heat removed from the cab to get you cold air has to go somewhere. That somewhere is making the condenser ~160 degrees or less when cooled properly. A garden hose would cool it off, but, because the hoses are always so short we use fans.

I read bad things specific to 3rd gens and aftermarket fan clutches. Either should work better than what you have now, but, for predictable long life results get the OEM clutch. As the shop recommended a fan clutch, well, I am X2 on that advice to the point that it isn't throwing parts at it and "hope". Do make sure the fan shroud is in good shape around the wire harness. I have had the best luck with OEM fan clutches for AC performance. (Except where specific aftermarket changes to lower the lockup temp setpoint have been made on a forgotten IDI diesel.)

When you see the cost of the pressure sensor the "just replace the fan clutch as R134a is cheap" may come to mind. Supposed to be a valve to allow it to be changed while charged, but, good luck that it will seal when needed. If you want to throw parts at it I will not fault replacing this sensor. Again a scanner should be able to see it's values and verify it's accuracy with an IR temp gun on the condenser with a R134A temp pressure chart. Lastly I would bet it's just an old fan clutch vs a sensor problem, but, this is without hooking the tools up to diagnose it.

Charging the AC system... These systems are charged by weight. Published procedure is recover and charge by weight. There is no charge by the gauge on the suction side like some half the cost of a AC shop recharge job cans like you to believe. This is expensive to do with the parts store "kits". System is a touch under 2 LB. 1 LB = 16 OZ. Most R134a cans are 12 OZ. How are you going to get a touch under 32 OZ in the system on 12 OZ cans without a scale? You can't and AC performance suffers with too low or too high of a charge.

 

[DannyW]

Mine has been degraded for years now. Somebody at Dodge ought to have their carcass deep fried for building such a piece of excrement. This is one of those many components that could easily have been designed to last for as long as I own this truck.

 

[Big_Horn]

Dammit @Tuesdak! You make way too much sense!! I'll order a new fan clutch and give it a try. I have a short and a long tow trip coming up here soon and I really want to ensure that everything is working like it should. I need to get this issue figured out before the winter hits. I run the defrost while the truck is warming up and the last time the system over pressurized, that's what I was doing. I will give an update on my progress.

 

[Big_Horn]

@Tuesdak, I do really appreciate your insight on all this...

 

[algonaman]

Wished I'd read this about the blend doors before I installed the inferior Heater Treaters. Damn.

 

[Big_Horn]

Now I'm thinking that the fan clutch gave out. ran the truck all day, came up to a stop light, vented r134 while in defrost...

 

[101st ABN]

I had same issue. A recharge of R134 helped but I had a tired fan clutch which showed itself only when towing heavy. Replaced with a mopar clutch. Passengers now comment on how cold it gets now.

 

[Big_Horn]

I had same issue. A recharge of R134 helped but I had a tired fan clutch which showed itself only when towing heavy. Replaced with a mopar clutch. Passengers now comment on how cold it gets now.

Funny you mention this... so in the past week I vented more r134. Once after morning startup, even though I turned off the defrost. Then after driving literally all day, came up to a stop light and again started venting. I replaced the fan clutch yesterday (Napa special) cause I really didn’t want to spend $650 from the steelership and am leaving on a trip in a few days. The old fan clutch seemed a little loose to have less drag in comparison to the new one but nothing real obvious. I guess time will tell...

 

[Tuesdak]

Mine has been degraded for years now. Somebody at Dodge ought to have their carcass deep fried for building such a piece of excrement. This is one of those many components that could easily have been designed to last for as long as I own this truck.

With all due respect someone who was at the Bankrupt "OLD" GM and/or their supplier is WAY more deserving over krap EV fan clutch design and a complete overall lack of cooling ability that won't cash the power check their vehicles write.

Does the engine oil last as long as you own the truck? Some things are a wear item and NVH prevents use of say a on/off style of clutch that may last longer (via no age failures) than the life limited silicone fluid used in viscous clutches. Garbage trucks with on/off fans are hours of operation limited in many towns after all.

IMO Cummins Dodge did a damn good job with the clutch and fan design. It generally worked till wear out for the most part unlike GM Trailblazer EV fan clutches that suffered all kinds of valve desegregation thus in warranty and out of warranty constant failures, redesigns, etc. Still a $500+ part for a Trailblazer. It was such a Bean Counter Design GM went back to the Obsolete Spring-Thermal clutches before their bankruptcy and end of Trailblazer production. 2008 Duramax trucks didn't get early marketing promises of a EV fan clutches for the same cost-cutting Bankruptcy reasons. Both designs in the era suffered from eating their wires: something FCA appears to have improved the design of today via a harness on the back side of the fan vs. the older front harness design.

The cost of OEM vs. aftermarket appears to be a legit gripe.

 

[nibroc]

interesting thread.........thanks

 

[Big_Horn]

I want to thank you all for your input! This is the reason I still remain a member and I must say, TDR HAS saved me money and gave me tons of projects bringing my truck to what it is today. You are right @nibroc, this is a very interesting thread. I have learned a lot about this AC system. I ended up Epps I g my fan clutch after popping the relief valve again. It seems to activate a whole lot more now, which is weird since I have no recollection of it kicking on (like it is now) when I bought the truck new. I run the defrost nearly 100% of the time, I did end up getting the NAPA brand since funds were tight and the dealership wanted $650! I don’t know if there would be a difference in activity between the stock clutch or the NAPA brand. Maybe someone could shed some light...