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Heater (and A/C) problem diagnosis

 
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Old 09 Nov 2018, 11:11 am
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Default Heater (and A/C) problem diagnosis

After having to replace the radiator, I'm back to trying to figure out the heater issue (the A/C isn't working either and it may be related but I just don't know).

The heater doesn't blow hot. Here's what I know:
(2010 PT Cruiser, 2.4 L)

1. Pulled the console and the temperature adjuster appears to be OK. The cable moves smoothly as you turn the knob from cold to hot and back again. When I turn the knob I can hear a little squeak as what I assume is the blend door moves back and forth. No change in air temperature at either hot or cold or whether or not the A/C button is pushed.
2. The temperature for the car goes up to about the half-way point, the drops down to between the 2nd line and the halfway line and levels out. I assume this is the thermostat opening up(?) to cool off the engine.
3. Neither hose (top or bottom) to the heater core is getting warm as the car warms up!
4. I flushed the heater core forward and back. Some rusty-looking fluid came out, but no debris. Still, no temperature change when I touch the hoses.
5. I have one of those big tub funnel things and I've bled the cooling system using that method (not the little bleed screw) warmed up until the thermostat opened. The car was slightly inclined at the front passenger's side to elevate the cap location.


Any help would be appreciated, it's about to get cold here in the NC mountains! Thanks!
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Last edited by McKinziesDad; 09 Nov 2018 at 11:25 am. Reason: Additional details.
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Old 10 Nov 2018, 08:37 am
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Default Re: Heater (and A/C) problem diagnosis

Are you running a 50/50 blend of coolant and water? If so, I'd try another flush. About the only other thing I can think of, you have already mentioned. That's the heat adjustment cable.
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Old 10 Nov 2018, 11:08 am
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Default Re: Heater (and A/C) problem diagnosis

Going out on a limb here.

I assume the heater system is the same on your 2nd gen as on the 1st gen cruisers.

On the PT, the hot coolant flows at all times from the engine, through the heater core and back to the engine. There is no water control valve.

The interior temperature control knob determines if and how much air flows through the heater core. All air flow passes first through the A/C exchanger; when the A/C is off, there is no cooling-drying action.

Some or all of the air flow then goes through or around the heater core.
The amount of air directed through the exchanger determines the cabin heat.

If the hoses under hood are not getting hot, you have either a bad thermostat, or blockage in coolant passages on the engine or in the metal pipes, to which the rubber hoses connect.
IMHO

It is possible that you when hear a squeak, the blend door is not actually moving.
When the A/C is turned on, you should get cold air from the A/C regardless of any heater core exchanger problem.


Quote:
Originally Posted by McKinziesDad View Post
...
The heater doesn't blow hot. Here's what I know:
(2010 PT Cruiser, 2.4 L)
...
3. Neither hose (top or bottom) to the heater core is getting warm as the car warms up!
4. I flushed the heater core forward and back. Some rusty-looking fluid came out, but no debris. Still, no temperature change when I touch the hoses.
...
Any help would be appreciated, it's about to get cold here in the NC mountains! Thanks!
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Old 10 Nov 2018, 07:44 pm
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Default Re: Heater (and A/C) problem diagnosis

Is your lower radiator hose about the same temperature as your upper radiator hose after the engine warms up?
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Old 12 Nov 2018, 01:31 am
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Default Re: Heater (and A/C) problem diagnosis

Did you personally install the thermostat that's in there now?
If so, what temperature T-stat did you use?

If not, it sounds like you have a 180F or lower thermostat rather than the proper 195F thermostat. You also may have either a mixer problem or a clogged heater core.

Removing/changing the thermostat is easy. You just need a 10mm socket and an extension plus a telescoping magnet to lift the bolt out after it's loosened all the way. If you try to pull the loosened bolt out with your fingers or long pliers, you are very likely going to drop the bold down into the engine and it can be a real pain to get out if it doesn't drop down to the ground. There are lots of nooks and shelves for the dropped bolt to get stuck on.

To remove the plastic thermostat housing neck, after removing the 2 10mm bolts, it's easiest to first remove the upper radiator hose at the radiator, then pull the housing and hose out toward the passenger side and either remove the hose on that side or simply lift the housing high enough to remove the thermostat. Remember, the thermostat coil faces down and the tab on the gasket needs to fit into the slot in the housing.

You can test the heater core by disconnecting the heater core hoses on the engine side rather than the firewall side and run a funnel of coolant or water into one hose and catch the outflow from the other. If it flows freely you are good to go. If it doesn't, you have a clogged heater core.

Here's a picture of my flushing of the heater core. I put the vinyl tubing into the core fittings on the firewall, but you could put them on the hoses with some barb fittings and you won't have to take all the connectors off the harness to get down to the firewall clamps. You can see where the heater core hoses connect with the clamps just to the right of the 1 gallon jug behind the wires leading to the camshaft posision sensor.


Last edited by rsrocket1; 12 Nov 2018 at 01:39 am.
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Old 12 Nov 2018, 01:18 pm
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Default Re: Heater (and A/C) problem diagnosis

Quote:
Originally Posted by chuzz View Post
Are you running a 50/50 blend of coolant and water? If so, I'd try another flush. About the only other thing I can think of, you have already mentioned. That's the heat adjustment cable.
I just replaced the radiator so the 50% coolant / 50% distilled water is pretty new. You still think I should flush it again? What am I looking / hoping for? A double check for a clog or air lock?
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Old 12 Nov 2018, 01:30 pm
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Default Re: Heater (and A/C) problem diagnosis

Quote:
Originally Posted by rsrocket1 View Post
Did you personally install the thermostat that's in there now?
If so, what temperature T-stat did you use?

If not, it sounds like you have a 180F or lower thermostat rather than the proper 195F thermostat. You also may have either a mixer problem or a clogged heater core.
Mixer? You mean the blend door?

I installed the thermostat and have a similar looking rig for flushing the heater core as you have in your picture. I attach mine at the end of the hoses instead of the firewall. Seemed to make sense to me to check the hoses at the same time.

I'll probably remove the thermostat and test it, just to be sure, as that's a pretty easy item to check off the list.

Thanks for the reply.
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Old 12 Nov 2018, 03:48 pm
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Default Re: Heater (and A/C) problem diagnosis

I don't think you need to remove the thermostat. If the temp gauge is sitting between the middle mark and the 1/4 mark, I think the engine is running too cool. Removing the thermostat will cause the engine to run even cooler.

Here's my shots of the gauge and the temp sensor readout at 152F and 186F





It should sit right near the middle mark for proper operation at 195F



Even at 208F, the gauge is still sitting on the middle mark

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Old 12 Nov 2018, 04:26 pm
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Default Re: Heater (and A/C) problem diagnosis

I should have been clearer, I'm not planning on testing the PT without the thermostat. I meant I'll test the thermostat using a pot of water and a thermometer. But those are pics are helpful.
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Old 13 Nov 2018, 08:19 am
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Default Re: Heater (and A/C) problem diagnosis

Well, since you did the flush and fill already, I'm going along with the consensus that the t-stat isn't up to snuff. You really need that 195 in there. As for the flush, I always flush my vehicles in both directions through the heater cores.
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a/c problems, blend door, heater, heater core, thermostat


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