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The heater in my 2001 has been less and adequate until I performed some modifications as explained below.

Performance has increased with the most significant improvement resulting from the recirculation / fresh air door modification.


Small wire rope clips were attached to the vacuum actuator for the recirculation / fresh air door. The door's movement is restricted, allowing fresh air in (about 50%) on the 'max ac' setting, and allowing recirculated air in on all other functions.

Some just modify to allow fresh air on 'max ac' however there is no floor heat on this setting. Using two wire rope clips as pictured worked out good.




I noticed that heater performance would increase with higher engine RPM, which suggested flow through the heater core was a factor. I had already flushed thoroughly with CLR and water (which made an improvement).

I suspected a clogged or restricted fitting and sure enough there was. The barbed hose nipple (1/2" NPT x 5/8" Barb) is actually an orifice of less than 1/4". Replacing the nipple with a full flow brass nipple made improvements on very cold days with the fan running on high.





I also cut a hole to access the A/C core, and used a 90 degree fitting on an air line to blow across the core. The blower fan was removed, and a shop vac used to capture any contaminants. The reason for this, the airflow seemed to be less than adequate and I suspected debris clogging the a/c core, which is first in line from the blower.


 

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Sorry, but CLR won't clean a stopped up heater core or radiator. I am sure if you flushed your block and replaced your heater core you would find your heater more than adequate down to about -60* F.
 

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Sorry, but CLR won't clean a stopped up heater core or radiator. I am sure if you flushed your block and replaced your heater core you would find your heater more than adequate down to about -60* F.
i flushed my whole system and have marginal Heater output, when its 30 out i still freeze in this truck, if i set the fan higher then 3 the air is not longer hot but marginally warm.

I'll try this to see how it works.
 

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I just found this somewhat ancient thread but I thought I would bump it. With the east about to get its butt smacked by winter again, it seemed like the thing to do.

My truck is up on blocks in the, (thankfully heated), garage and this thread spurred me to check the heater inlet fitting on the engine.

Mine also had a tiny 1/4" hole in it. It's 4am so instead of going for a brass barb, I just drilled out my steel one to 7/16". The whole process took about 5 minutes.

Hopefully it will also be a bit quicker about curing the air lock which inevitably happens any time I play with the coolant.

I haven't run the truck yet since I'm still working on the trans but this should improve heater flow significantly.

I am also planning on doing the heater core cleaning trick. I have had the fan out and I know there is all sorts of crud on the condenser. Since it is first in line of the HVAC system, it acts like an air filter...not the best idea ever. I did a similar thing with my Grand Cherokee.

Nice work asheng.
 

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i solved my issue, i have foudhn a true 195 T stat works wonders.

the 195 from NAPA actually runs the motor around 190-193, and the heat is blaring hot.

its amazing how different the heat output it when the motor is 190 vs the cummins t-stat of 175
 

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I have a 195 thermostat and at anything above -15c, (5f), it gets hot. At -30, (-22f), it's warm, but not hot. I'm looking for hot. I think this will make a difference.
 

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Gonna try some of these tips on my 02 tomorrow if I can. My heat is pretty much non existent. My fan switch only works on high right now. Has anyone else had this issue? Im assuming bad fan switch....
 

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After eliminating the restriction in hose barb, you may experience a unpleasant buzzing from heater core. The restriction reduces flow and PRESSURE to heater core.
 

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Gonna try some of these tips on my 02 tomorrow if I can. My heat is pretty much non existent. My fan switch only works on high right now. Has anyone else had this issue? Im assuming bad fan switch....
Gsxguy - Your blower motor resistor is shot. I had the same problem. I pulled the resistor out and had a couple of pieces of the ceramic come out first. When the resistor came out, the ceramic block had a crack in it. I re-soldered the brass arm back on (pretty obvious situation with the resistor in hand.) Re-installed resistor and been working since, couple of weeks now.

The resistor is in the cab, passenger side footwell. It is mounted on the bottom of the HVAC box near the tranny hump. Two phillips head screws and an electrical plug.
 
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Gsxguy - Your blower motor resistor is shot. I had the same problem. I pulled the resistor out and had a couple of pieces of the ceramic come out first. When the resistor came out, the ceramic block had a crack in it. I re-soldered the brass arm back on (pretty obvious situation with the resistor in hand.) Re-installed resistor and been working since, couple of weeks now.

The resistor is in the cab, passenger side footwell. It is mounted on the bottom of the HVAC box near the tranny hump. Two phillips head screws and an electrical plug.
Thank you Ill give it a shot once it warms up alittle around here :thumbsup:
 
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