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Heater Barely Blowing and Not Very HOT!!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Nitrodrip350, Nov 4, 2002.

  1. Nitrodrip350

    Nitrodrip350 1/2 ton status

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    Ok to start off I have a 160 thermostat and all the emission crud has been removed. Still have the ball shaped valve on the firewall (yes I did remove it then realized it actually does something!) When I turn on the heater it takes a mad amount of time for it to even warm up. I think that this may be from the low temp thermostat, so I'm going to change that unless anyone else has some ideas. Also when I turn on the vents/heater it blows with about as much force as a mouse fart!! It is warm but not heater warm, more like under the hood warm. I remember when I first bought this it was like a oven. I went through the search option and someone spoke of a valve that can break and not let the hot air from circulating, also is the opening/closing of the heater/vents controlled manually or by vacuum? I'm almost at the point of just pulling the heater core out and installing one of these:
    http://store.summitracing.com/partdetail.asp?part=26592&view=257#largerimage

    Someone please /forums/images/graemlins/1zhelp.gif

    Thanks for the Help,
    Shane - /forums/images/graemlins/grin.gif
     
  2. TopOff

    TopOff 1/2 ton status

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    First verify you are getting water flow to the heater core.

    Is this an A/C equipped truck?

    Second, why does your blower motor only feel like a mouse fart?
    Fix that! /forums/images/graemlins/smirk.gif

    Good luck.
     
  3. imiceman44

    imiceman44 1 ton status

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    If the vaccum line is not connected you will have air going to every opening and yes it will feel like a mouse fart.
     
  4. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Mouse Fart! /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
    If the blower motor is not realy putting out so to speak check the heater resistor next to the motor on the fire wall. if its good replace the motor! I Just went throught that!
    Bill
     
  5. Nitrodrip350

    Nitrodrip350 1/2 ton status

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    Sounds good I'll check the resistor and see if that is still working correctly, also the heater core is new and both the hoses have been replaced. I think that the next main step on the truck is go through everything under the dash now and make sure everything is hooked up correctly! I've got a feeling that this is easier said then done!!

    Thanks Shane /forums/images/graemlins/grin.gif
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    It's important to whether AC or non AC, since non-AC setups are purely mechanical (cable controlled) while AC is a mixture of cable and vacuum control IIRC.
     
  7. Nitrodrip350

    Nitrodrip350 1/2 ton status

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    /forums/images/graemlins/blush.gif Sorry forgot to leave that info, it was originally a AC equipped K5. So I guess this makes it even more fun to track down right!! I do notice that when I change from the Vents to the Heater it has to be perfect or they won't come on. But even when they are finally on it still barely blows. Also they won't come on when it's cold, truck has to warm up a bit before they kick in. /forums/images/graemlins/confused.gif

    Thanks Shane /forums/images/graemlins/grin.gif
     
  8. TopOff

    TopOff 1/2 ton status

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    That's how my fan worked when I first got it.

    The fan would move slowly until it warmed up a bit. Then I it worked pretty good. When it got cold out (going up to Tahoe) the fan would squeak. I ended up replacing it. Checking all my vaccum actuated flappers, and mechanical flappers. I also found the flapper which moves from the COLD AC side to the heater side was broken. I used some 5 minute epoxy and it works, looks like crap, but it works.

    Then I checked and redid all my vent routing. That was LOADS of fun!

    Good luck.
     
  9. milspecjimmy

    milspecjimmy 1/2 ton status

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    mine works good on every position except "HIGH". its a new motor, and it blows the fuse when i put it on high. any ideas?
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  10. TopOff

    TopOff 1/2 ton status

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    Sounds like your motor's bushings are shot too. I think these only last about seven years or so. Mine squeaked last night for a brief amount of time then it was fine.

    I would take your motor out, and spin it by hand and see how it spins. If it has any sort of bind in it, go ahead and get a new one. It would be worth it this winter!

    Good luck.
     
  11. nofeartruckin00

    nofeartruckin00 1/2 ton status

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    If it weren't for the popping fuse, i would put my money on the relay. There are 4 "sections" to the relay. I guess the first 3 positions get the voltage run through different sized inline resistors, and the 4th, High, position gets the full 12 volts pushed to the motor. Might want to take a look at that relay, should be on the fire wall, passenger side i think.
     
  12. milspecjimmy

    milspecjimmy 1/2 ton status

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    forgot to mention that i replaced the relay last night
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd probably check to see if the 12V wire is shorted to ground somewhere. Check continuity between it and ground. If you've got continuity, you've got a break in the wire somewhere.

    Also check the switch assembly itself. These are pretty simple setups, as I recall one brown 12V wire from the fuse panel to the switch, and 3 wires "out" of the switch to the blower motor is all. (at least in non ac apps, ac apps may have 4 wires out from the switch)
     
  14. milspecjimmy

    milspecjimmy 1/2 ton status

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    ok i changed out the switch with a new one, put on a new relay and jumped the 12v wire that goes into the relay with the feed to the motor, and it works fine. then i pulled the motor to se how free it feels. spins fine. i have 25 amp (what its supposed ti have) in each of the two heater spots on the fuse box. the truck also has A/C wich is disconected. any ideas now? i am stuck!!!
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Are you still blowing the fuse when on high or what? This is why I don't advocate changing parts without knowing what the problem really is...
     
  16. milspecjimmy

    milspecjimmy 1/2 ton status

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    checked every thing first, found out that the relay was bad, replaced that. put it on high then ZAP blown fuse, then pulled motor, chcked for free moving. tried a second relay just in case. ZAP. still blows fuses. jumped the 12 in to the relay to the out put to the motor, blower works fine and will move the dirt on the floor mats. hooked it all up. looked for shorts, and checked with a meter. still pops fuses.
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    I dunno.

    Reasoning:
    Switch works. If brown feed wire from fuse panel was bad, fuse would always blow.
    Relay works. (wouldn't have other speeds if it didn't)
    All wires to relay itself work. (see above)
    Motor works. (jumping 12v forces it to)

    Looking at the AC wiring, which I have not much experience with, it appears the selector (bi lev, etc) has some wires running to it. I didn't think this was the case, but the manual shows color coded wires. Aren't those all vacuum controlled, and the only wires on that thing on the blower speed switch?
     
  18. imiceman44

    imiceman44 1 ton status

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    I would check for a shaffed wire from the control switch to the motor, when you switch it on high, you get a short, and blow the fuse. It's the only explanation now.
     
  19. milspecjimmy

    milspecjimmy 1/2 ton status

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    if i unplug the relay, it will not blow the fuse, and i checked the ohms between the 12v feed wire and ground, with the switch in all positions and it is fine
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  20. creampuff90k5

    creampuff90k5 1/2 ton status

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    Um, I don't know about fixing the fan speed, but I can tell you that the 160 degree thermostat sucks for heating purposes. When I moved up to NJ from FL, I swapped to a 180 and that still wasn't enough. Now I run a 195 and the heater works great. Surprisingly, doesn't run too warm in the summer either.
     

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