no heat from 94 jimmy

Discussion in '4X4 Truck Talk and Repairs' started by FLETCH, Feb 27, 2009.


    FLETCH Member

    Villisca Iowa
    Yea I'M havin some trouble with this jimmy I just bought it don't have any heat put a new thermostat in it and still nothin it just acts like it ai'nt building up enough pressure I LET IT RUN FOR QUITE some time and felt the radiator hose but it didn't feel really hard it's not leaking any fluid or any thing and I checked the radiator cap it's brand new but I WONDER IF the GUY i bought the truck from got the correct one any idea's from anyone. thank's.

    CHAVEZ CHAVEZ New Member

    might check the fuse , and the heater fan motor .

  3. smokey869

    smokey869 New Member

    you need to check the heater hoses to see if both are hot, these vehicles are very prone to plugging heater cores, you can usually flush them out with a hose, but if not they can be a bear to replace, if it has electric controls the motors go out at times too, usually in behind the glove box, if you can see it watch it while you change from hot to cold and back see if the arm swings on the heater door
  4. Wabash River Bear

    Wabash River Bear New Member

    If the heater core is clean, and the motor is building heat, its probably airlocked. You may need to purge the lines to the heater core.
  5. larry again

    larry again Active Member

    no heat,double check the thermastat first, for proper instalation and heat range 192 degree.see if you have a heater control valve,if you do see if its working check vacum.if both heater hoses are hot you mite have a door problem under the dash.check the thermastat!!!!!!!!!!!! hopes this helps.
  6. Bill in SC

    Bill in SC New Member

    South Caro
    We just got done unstopping a clogged heater core today on a farm GMC pickup. Apparently, and I just learned this today, if you use the wrong kind of antifreeze, it can cause problems. The GMC line of vehicles uses the red type antifreeze, and if you mix it with the green stuff, it gels up like snot, and will clog the heater core. Again, I just learned this today from a rather knowledgeable person. Anyone else ever heard this?

    Bill in SC
  7. Poppa

    Poppa New Member

    Pinson, Al
    I don't know about your truck but some models have a valve in the
    header hose lines going to the heater core that stops the circulation
    to the core in the summer time. The valve might be bad or stuck.
  8. Cattn-Jeep

    Cattn-Jeep New Member

    This is going to sound dumb, don't get mad. Check you coolant level in the overflow. Too many times peoples heaters go out and all that's wrong is the engine coolant level is low.
  9. jkm4874ford

    jkm4874ford New Member

    Bowling Green,
    Had this happen on the daughters 2000 blazer. I used a garden hose and flushed the system every which way I could. Have had no problem all winter. And do not mix coolant types, will cause problems. Stay away from the red stuff. There are web sights explaining all the same replies posted here.
  10. cantstopgrandma

    cantstopgrandma New Member

    1994 probably has the Dex Cool in it (its actually orange). This is a very common problem with Dex Cool. Dex Cool likes to eat gaskets, and also likes to plug up heater cores and engine cooling systems. If your coolant isn't low, i'd put money on it being a plugged heater core. I'm having the same problem with my '98 s10 right now, partial heat, i just haven't had time to fix it. As has been stated, dont mix it with other types of coolant, as it will gel and cause even more problems. I am all too familiar with dex cool, i've had to have intake gaskets put in my truck and my wife's chevy car, and seen several from work have 2 and 3 sets of intake gaskets and head gaskets over the life of the vehicle. As the mechanic told dad, when his 99 silverado had no heat a couple months ago: "Common problem, we usually flush the system out real good and get rid of the Dex Cool". This is one of GMs dumber ideas. If you decide to refill with Dex Cool, keep it flushed often to avoid other problems. Does that Jimmy have the 4.3 V6? If so keep an eye on the intake gaskets....common problem for this motor. Dex Cool causes the crappy plastic gaskets to get brittle and they literally crumble (i've seen it). I used to be a die hard chevy man, but i'm getting tired of cooling system problems, and having to have the tops of motors pulled off to fix intake leaks.

    Edit: Fotgot to add, GM hasn't had a couple of class action lawsuits pertaining to Dex Cool for nothing....consider yourself warned.
  11. psychomekanik

    psychomekanik New Member

    This is very correct. dex-cool is a 100,000 mile coolant that turns to an acidic grease in 60-70,000 miles. It also cause problems with head gaskets which in turn can cause the symptoms you described. (air in system) If any of you guys out there want to use the long life coolant without the problems of dex-cool, use the mopar h.o.a.t. long life coolant. this stuff is still clean and pink/orange at over 1000,000 miles. I'd make sure the engine temp is actually stabilizing. (look at the guage) then as stated feel the heater hoses. Is 1 hot and 1 cold? If so time for a back-flush. Hook up a garden hose in the opposite direction of normal flow and let it flush clean. There are solvents you can add first to loosen the crud. Add them and let it run till it's hot, then let it cool to work on it. if both of your heater hoses are hot, you might have a problem with the temperature blend door in the heater case. Inside the car, turn the heat dial from cold to hot quickly and feel the heat. Does it change at all?? if not, listen for the door moving. If it doesn't change even a little, the door could be hung up, or have a bad actuator. (door motor). Then last but not least. If you have a head gasket leaking compression into the coolant system, you can get airlocked. there's a simple test 9chemical block test) to determine if it has a bad head gasket. Let's not go there yet until you check the core and the blend door.