Heater fan only works on high after replacement of heater core
I changed the heater core on my mom's 2001 Chevy Prizm. Upon completeion the heater fan would only run on high speed. I can hear a faint noise when I turn the fan to low but the fan does not turn on until the highest speed setting. I asked my mom if this was a pre-existing problem and she said that, on low speeds when it was very cold out, -20F, it squealed for a while until it warmed up but that was it. Please let me know what this could be or how to start the trouble shootong process for this problem. Thank you.
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Re: Heater fan only works on high after replacement of...
It's very possible the fan motor has quit. The squealing noise is caused from motor bearing failure. As the bearings wear out or dry up the motor is harder to turn and require more current to run the motor. On lower speeds, the motor runs off a series of resistors that reduce the amount of voltage and current so the fan runs a lower speeds. If the bearings are worn, there is not enough voltage or current to turn the motor and that'sprobably the humming noise your hearing.
Good observation by the way.
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The heater core in 1985 was still accessed from the engine compartment. After you drain the cooling system, disconnect the heater hoses. They should be 2 different sizes so take note of which one goes where. Unplug the electrical from the case and then unbolt it. Pull it off and replace the heater core.
If you have A/C then it is a little more complicated. After you remove the heater hoses there is a retaining bracket and ground strap that have to come off first. Then take off the rubber seal and screen. The right wiper arm needs to come off next followed by the diagnostic connector, high blower relay and thermostatic switch. Now you can unplug the electrical from the case and the top cover and screen and take the heater core out.
Once you have it back together, when you go to bleed the air out of the system, make sure the heater is turned on maximum heat and the fan is on high. This will ensure that coolant goes through the new heater core. Hope this helps.
If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired. Heater Housing
The heater housing is usually under the dash and must be removed to gain access to the heater core.
Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.
The heater housing is disassembled to get to the heater core.
Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
Remove the heater coolant hoses.
Remove the cable and/or vacuum control lines (if equipped).
Remove the heater core securing brackets and/or clamps.
Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
To reinstall the heater core, reverse the removal steps.
When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.
Hello Justin. If your thermostat has been replaced with the proper one your engine is heating up. The problem then becomes twofold. The amount of coolant/antifreeze flowing through the heater core or a problem with the airflow over the core inside the heater plenum assembly. I would check for coolant flow through the core first. If the heat feels like it is warmer coming out an outlet with the fan on a low setting rather than a high one your heater core isn't flowing enough. To verify you can also check the two hoses that go through the firewall to your heater core once the vehicle has been warmed up, feel the temperature difference between the two. They should both be almost hot enough not to hang on to and close to equal temperature. A hand held temperature gun is really handy for doing this. If one is hotter than the other your heater core has restricted flow and will need to be flushed or replaced. Next is to check your temperature blend door operation. Move the control to hot and cool and listen for the door to move and feel for the temperature to change, if it does at all. The fan on low setting is best to listen and feel temperature changes. If you feel a temperature change or hear the door thump at each end of it's travel it is OK. If you have more questions on this problem leave it in "add a comment" and I will return your question.
Why do you think you need a heater? Has the fan stopped blowing or are you referring to the need to replace the leaking gasket in the heater core?
If you take it to a mechanic for the heater core gasket, you can expect $1200-$1400 just to replace a $0.80 part. It is very labor intensive but can be done yourself if you have about 6 hours.
if it has a back heater either a water line to the heater core broke or the heater core for te back heater sprung a leak probabley the heater core on the back heater replace either the hose or the back heater core whatever is leaking.
Notorious for plugged heater cores. Also updated plastic restrictioncouplers mounted at heater core available from dealer. Try back flushing heater core. Run engine till its at operating temperature then carefully hold the inlet and outlet hose breifly with heater fan on high if hoses are nearly the same temp then flow is good , if not then core is plugged.
Sounds exactly like what my mom's car was doing as for the blower only working on high. It was the resistor... I assumed it was the climate controls and replaced them but it didn't change anything then i thought that i must be the blower motor and replaced that too but it turned out to be the resistor which is under the dash on the passenger side of the car.