I have been having some trouble getting any air to come out of the vents after atleast 20 miles have gone by. It blows nicely and then after 20 miles or so you can barely feel anything come out of the vent. I thought it might have been a vacuum issue but I don't feel anything out of the defrost vents when it is doing this either. The fan always sounds the same, making a ton of noise but something is cutting all the air flow off. Any ideas? :confused:

Check your fuse...Check the fan phyiscally for damage...Pull the fan resistor out and check for damage...I've pull a few out now and seen that the fan takes alot of abuse from dust and dirt. The bearing tend to fail blowning the fuse most times. Also If you like most people here the keep jacking fuses into it till it won't hold a fuse. Typically the speed sresistor will burn up from the excessive load from the bad blower motor. The fan and resistor are on the passenger side pointed towards the floor board. Once you pull the blower out you can check for rats nest or debris. I've been lucky and pulled a $1 dollar bill out my buddy's 92 Cummins... LOL That was his whole problem was the 1 dollar bill was blocking part of the evaporator...

I will have to tear into it all. But its just that it is not an all the time thing. It is fine, then after a while it stops putting out the air, the noise is the same but it seems to not put any more air out the vents at full blast than it does on the lowest setting. Usually I end up going down to the lowest (when it is working!) and then it stops blowing so I have to crank it way up, then I notice it will spontaneously start blowing more air at some point. But I guess something could be going in front of the blower then moving out of the way, who knows. Lets Tear Down!

Took the blower fan out and it is mint. Any deeper than that looks like some serious work. I am going to have to stick a camera inside there to see anything. I felt some stuff at the base of the heater core part so I will have to vacuum all that out. :confusedAlright, I have a small favor to ask. Can one of you see if your floor vents blow out anything on any setting but the floor one? I seem to have some blow by going on down there, not too much and setting it to floor or floor/head vents does kick the floor up a bit. I am just wondering if it is supposed to have some flow down there regardless of the setting, or if I actually do have a door not sealing the floor off correctly.

I wonder about a mouse nest? I had mice in the cab... trashing tissues... I solved that by stuffing stainless pot scrbbers (SS Steel wool) into the cowel drains behind the hood hinges. The rain water still seeps through but no mice since. I live in the woods & trying to keep mice, etc out is a sport! Try vacuming everything you can reach... either way you'll learn. Air restriction might not respond to blower speed. If the flapper valves don't move... if could be a vacume problem... as in engine vacume/contols.Russ

I looked under the cowel, stuck the camera in all the holes under the dash and never could find a trace of anything but some dust. I have never had any mice in the truck anyways. I thought it was a vacuum problem too, but the default is to go to defrost which it never did.. With the blower out it sure as hell blows a ton more than I feel coming out of the vent. I'll run some more tests on it :thumbsup

Is there a thermal protect on the fan motor? Is there an intermittant connection or wire that opens when the motor gets hot? Set it on the floor, jumper the ground connection... let it run for a half hour. While thats whirring away, check all inlets, outlets with a flahlight, wire & shop vac. I've not had luck screening my Cirus heater so must be due for another mouse eviction. (I like 1/4" sguare hardware clocth or better yet aluminum expanded gutter guard {maleable} for screening engine & cabin air intakes.)Russ PS What are your heater controls set at? Some run to achieve a set temp... if achieved the fan can change speed. Not sure if Dodge is one such... Too d*mn fancy for me! (Or an I threatened by a vehicle with a higher IQ than me?)

I think Russ has a good idea of jumper testing the fan and see ifit holds up for a long period of time.

PS What are your heater controls set at? Some run to achieve a set temp... if achieved the fan can change speed. Not sure if Dodge is one such... Too d*mn fancy for me! (Or an I threatened by a vehicle with a higher IQ than me?)

Nope... As far as I know of there is no auto control fans...

While thats whirring away, check all inlets, outlets with a flahlight, wire & shop vac.

Boy Russ you must of had fun cleaning out those critters eh??? LOL I think there could be a piece of paper floating around in the vents too. Laying down when off but takes some time to flutter up and stick to a heater core or evaporator??? :confused:

Sometime prior to parking my old 79 C30 tow vehicle in the barn... fogging the 454 for storage...

I was getting ready for our annual Rendezvous camp. I drove the Chevy all week, ran like a bear... hooked up the trailer, loaded & pulled out of the house. We live on a steep hill... to get out you drive down the hill across 2 brooks & pull the 45 degree angle hill on the other side.

Half way up, the truck was not pulling right. I stopped & lifted the hood... truck sat there purring. I tried again, blowing a cloud of black smoke from the gasser! I checked the choke to see if it was stuck... it was not, it was wide open. The third try, same result, I saw specs of paper in the filter. I pulled the factory cold air hose & it had about a whole roll of paper towel in there shredded into a mouse nest. I was pretty hot under the collar by this point, & I scoopped the nest (it turns out mama mouse & all) & flung it discustedly into the street. I'm not one to litter but this was aboout the last straw.

At this point the person in front of whose house I'd stopped came out to see if he could help... just in time to see the litter hit the ground! I assured him I'd found the problem. I finished the clean out & scooped the litter into the horse trailer.

The truck pulled the 45 degree hill from a standing start, gaining speed the whole way. (Gotta love a 454 except at the pumps.) For the record it got 11 loaded or empty.

When we got home from 'vous, I put a wrap of... gutter guard inside the inlet & ran a screw through the plastic to anchor it. Mizz mouse had to find a new home.

I figure that running empty, it just didn't need that much air... once I put a load on it did & could not get it...

I sold the 79 to a guy last year. WE fired it up in the barn A cloud of blue smoke as the MMO (I used to use for fogging) burned off. He drove it off with a delightful rumble that echo's through my mind... it almost broke my heart...

Russ

79 Chevy C30 454, Comp Cam towing cam, Edelbroc timing chain, Edelbrock intake, Carter AFB carb, headers through oversized pipes & big mufflers mufflers, automatic/3.73 rear axle 16.5" rims.

I really dont think it has anything to do with the fan. It is louder than hell and hardly anything comes out. I closed the 2 passenger vents and found myself turning the A/C off of recirc and on low and turned the temp control up a little. So whatever I did (nothing so it will surely be back) has made it work. It was only 75 out though so we will see what happens when it gets back to 85.

ISX,I think you're right... if the fan runs (& I reread your original post where you said it continued to run)... then there has to be something else blocking the air flow...Are you missing any papers off the dash... fallen down in the vent?

Nothing but dust in there. Still hasn't got hot enough to test it again. >

OK, I'm going to take a wild shot in the dark... The fam is running but you're running the A/C. After a certain amount of time, the cold stops but you can hear the fan running. There's nothing wrong with the fan.The A/C fluid has almost all leaked out. There's enough for an initial blast of cold but not enough to keep the system running.There's a crack in the cooling unit behind the friggin dash. Dodge is known for this. The whole dash has to come out in order to replace (according to the guy that fixed mine). Most of the charges were labor. A tech will refill & add a an ultraviolet dye. There's an overflow hose in the engine room, the dye will show & prove the leak. You might get a year on the refill if, like mine, it's slow. I'm sorry to be the one to tell you...RussPS. I have MS & like most with it, I don't do well in the heat. Several years ago, we were packing up from our Rendezvous camp... The first days of June... The tempature soared to 95 (according to the Dodge temp guage once we got moving). I was really suffering, helping load... I had to use a mist spray every 5 minutes just to keep going. I looking forward to cooling off & the friggin A/C gave me one blast & then just warm air. I was not a happy camper.

Following Russ's lead here... http://mopar.mopar1973man.com/cummins/2ndgen24v/ac/ac.htm

Following Russ's lead here... http://mopar.mopar1973man.com/cummins/2ndgen24v/ac/ac.htm

Thanks, mines not functioning. Where is the inlet for adding refrigerant? Not sure! :confused:

No no LOL The A/C still works. Everything still works, the heat a/c, everything, the air flow coming out of the vents just almost stops. Fan keeps running but for some reason it doesn't make it all the way to the vents. I swear there must be some air doors in the dash screwing up and closing off all flow to everything. I looked at it all and it has worked fine since. :confused: As for the A/C inlet, its behind the passenger headlight, up by the hood rubber gromet thing..

Mice chewed off yer vacume lines?

Mice chewed off yer vacume lines?

If so then it would fall back to DEF mode all the time... :confused:

Exactly, which is why it is throwing me for such a loop. Maybe its backfeeding it through the cowl LOL

It PO'd me when the mice chewed through the windshield washer hose on my Cirus. I've trashed all the hood insulation to remove the attractive habitat. I know, this does not help your problem at all. A lot of stuff is vacume activated... dunno where the pick off point is.'Russ

Could it possibly be something to do with the heat/defrost door actuator, section 24-26 (shows as page 2755 on my computer) of the FSM? Just a passing thought as it was a quick glance I made.