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    #1

    Cold heater, need to know components location(s)

    After some time diagnosing the heating system the other day with the temperature gun, I found out that my radiator is partially clogged (temperature ranges from 170f to 70f at random places). But that is no reason for the heater not to blow hot air. Touching either of the heater hoses with the temperature control lever at full hot position revealed that both inlet and outlet hoses are cold. Which means that there's no coolant going in or out from the heater core. Blower works very good, and the flaps in the airbox works as they're supposed to.

    Now, the Chilton manual I have mentions a heater control valve, the one that's supposedly is somewhere in the engine bay, before the inlet. But it doesn't show nor suggest a location. I'm hoping those with Mazda FSM can help me through illustration.

    It's getting cold, and having to turn on the a/c to help de-frost the windshield on a 30 minutes one way daily trip sucks.

    The idea is, once the heater control valve location is revealed, I'll by-pass the valve and see if the hoses and core are getting hot..
    Tags: None
    #2
    I hope for your sake it is the by-pass valve. To replace the core is such a job that I hope :crosses fingers: I never have to undergo.

    Best of luck and keep us updated. Oh and check your PM's
    The T3 BP MX-3 conversion has begun, and is taking forever & will kill me.

    Comment

      #3
      Yeah to get the heater core out you have to remove the dash. I've yet to find the bypass valve if there is one. I've been looking believe me. It's cold up here too and my Heater dosn't work either!

      Comment

        #4
        I have been facing a similar problem... but i havent checked the hoses in the engine bay since its been snowing and freezing for the past few days...

        but what do I have to check to make sure that its not the heater core?

        Comment

          #5
          Originally posted by whistler
          I have been facing a similar problem... but i havent checked the hoses in the engine bay since its been snowing and freezing for the past few days...

          but what do I have to check to make sure that its not the heater core?
          try and record the tempature of the coolant going into/out of the heater core.
          When you turn your car on... does it return the favor?

          Originally posted by goldstar
          Yes, still have it. It was my attempt to immortalize you in verse.

          A Protege driver named Brock
          Once said 7 seconds he'd clock.
          So his engine he goosed
          With much too much boost,
          And drove a rod through his block.

          Comment

            #6
            it's the core guys... clogged core... there's no control valve in this car. So today I spent most of the day disassembling the whole dashboard. At least I managed to get the central airbox (where the heater core is) out. It's hell.

            but the clogged core is not the only contributor to the cause. Seems there's a glitch in the electrical side of the cooling system as well... As soon as the water temp. reach operating temp., the cooling fan just stays on, 24/7. If it's in summer, then it's fine I suppose... but having the fan ON all the time pretty much drew away what little heat generated by the otherwise quite efficient cooling system on the car.

            I've checked if the fan control was hardwired or bypassed, and it's not, it shuts down once, but remains ON for the majority of the time. Something that the ECU reads trigerring it ON.

            After learning the flow diagram, I figured, about the only coolant control valve there is in the engine bay is underneath the intake plenum, and it has more to do with cold/fast idle control. And my cold idle performance is fine so far (no higher than 1500rpm, no chopping).

            Hopefully tomorrow going to be a downhill with no surprises...

            Ps: D323, thnx for the early x'mas present man.

            Comment

              #7
              you can try replacing the fan relay, it's about 6-7 bucks at autozone. autozone is the only place locally (other then the dealer) that i could actually find one at.

              93' 5spd DX
              R.I.P

              Comment

                #8
                so the heater core is behind the middle vents above the stereo under the dashboard?
                I need to check to see mine too... hopefully its not the core... its so cold outside, cant do squat at anytime.

                Comment

                  #9
                  tsk tsk tsk... Silly you TheMAN, the thermoswitch only exist in auto tranny model, not manual tranny model (any monkey that can read the FSM will know it).

                  Non-automatic tranny models got a blank plug in place of the thermoswitch.

                  If by thermoswitch (since there are 2 mentioned in the book) you're refering to the temp. sender at the thermostat neck, then that's not the case.. Sender was replaced when the old one broke in pieces. AFAIK, this sender responds to both eht ECU and gauge cluster.

                  whistler, in short, the heater core is above the center tunnel, behind the stereo. It's installed within the central airbox. If you manage to save the quick-fit connectors for the hoses, that's good, otherwise you can always bypass the additional connector and clamp the hoses straight to the core.

                  If this core replacement doesn't yield as good a result as hoped for, then the next thing inline to inspect is the oil cooler and pipes into it, as that's where the heater core got its' coolant. (humm, neat, my nissan doesn't even have oil cooler, my older mr-2 did)

                  Comment

                    #10
                    Originally posted by Asura
                    Ps: D323, thnx for the early x'mas present man.

                    no problem d00d. Use it well, as I know I have. Oh and sucks to hear you had to replace the core. I have heard the horror stories/seen the pics online.

                    Good luck, and hopefully the new core solves all your problems.
                    The T3 BP MX-3 conversion has begun, and is taking forever & will kill me.

                    Comment

                      #11
                      Originally posted by TheMAN
                      ok genius, explain how the fan circuit is hooked up on 1st gens... tell me there isn't 3 different coolant related sensors at the back side of the head
                      tsk tsk tsk.....
                      you are indeed a genius... yup, definitely... you have to be a genius to recognise another genius. I don't even know I'm a genius until you told me so. Listen, I don't appreciate someone entering a discussion saying "wtf". You dig? good. Now, behave before I slave you.

                      Your wtf post is not helping here.

                      EDIT: FYI, new heater core is in, coolant burped, all good. Hot heater finally. Can't believe how clogged up the old core was when I split it open.
                      Last edited by Asura; 12-21-2004, 10:43 PM. Reason: avoiding dbl-posting

                      Comment

                        #12
                        how much did you pay for the core? I was quoted arround 70.00. I really don't want to pay that much. Taking the dash out isn't a problem. I don't think the cops will mind me driving the car arround without a dash in it do you guys? LOL!!

                        Comment

                          #13
                          I got mine for $105 locally... Wholesale price was $101 in my area. So I'd say $70 is very good, if it's a NIB.
                          As for the cops, I hope not either, but I won't suggest it. If there happen to be an idle cop, and he spots you driving around without a dash and speedo....i don't know, maybe a "fix it" ticket?

                          Comment

                            #14
                            sorry for the newbie question, but how do i exactly check the temperature going and coming out of the heater core? which hose in the engine bay is for checking?

                            also is the heater core responsible for the rear window defrosting? coz the defrosting seems to be very very slow... almost like nothing's happening.
                            thanks in advance
                            Last edited by whistler; 12-22-2004, 06:53 PM.

                            Comment

                              #15
                              Originally posted by whistler
                              sorry for the newbie question, but how do i exactly check the temperature going and coming out of the heater core? which hose in the engine bay is for checking?

                              also is the heater core responsible for the rear window defrosting? coz the defrosting seems to be very very slow... almost like nothing's happening.
                              thanks in advance
                              you will have to measure the temp on the hose that runs from the block to the firewall

                              the rear window defroster is electric. those orange stripes across the rear is the defroster.
                              When you turn your car on... does it return the favor?

                              Originally posted by goldstar
                              Yes, still have it. It was my attempt to immortalize you in verse.

                              A Protege driver named Brock
                              Once said 7 seconds he'd clock.
                              So his engine he goosed
                              With much too much boost,
                              And drove a rod through his block.

                              Comment

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