Heater issue (1 Viewer)

[MrWhiplash]

Hey all,

It's started to get a bit chilly up here in the north, so I've had to kick the heater back on in the mornings. Recently, as of about two weeks ago, the heater works great once the vehicle heats up and lasts about 90% of my drive to work. My drive takes about 20 minutes, and in the last couple of minutes, the heat just stops. It blows what feels like lukewarm air, it's not A/C cold, but it isn't very warm either. This is the first time I've had any sort of heating issue, and I want to tackle it before things get really cold out. With my limited knowledge, I was thinking maybe the heater core is going out?

Anyone else have any suggestions?

Thanks!

 

[Felde]

Hi
What vehicle exactly?
Either a) no or not sufficient amount of hot coolant is making it to or through the heater core any more (obstructed or clogged) or
b) the core doesn't exchange heat to air any more, which probably means the core is broken and lets the coolant take a straight in - out. In worst case, 'out' means out of the core onto the floor.
Let's go for the first thing first..
Check your floor / footwells: Any wet?
Check coolant level.
Check the heater main valve (Usually located in the engine bay on the firewall) Linkage OK and really fully open?
Check hose from engine to valve, with engine running & hot: Not kinked, being under pressure & hot?
Check return line from heater to engine. From cool: Drive truck warm, with heating off. Check return line temperature: Should be quite cool.
Now (engine running, still) turn heating on, blower off: Return line should become warm(er). If so, at least coolant makes it trough the core. Question then is: Is it sufficient volume and is it passing the exchange core or just passing straight through?
You can detach the heater circle from the engine and check by applying a controlled flow of liquid. If clogged, you should note.
If not any clogged or obstructed, the heater core is likely to be the culprit, I recon.
Good Luck Ralf

 

[clintnz]

All great tips above, but it's weird that it works well initially.

Just a guess as we don't have real cold conditions much here, but could it be that the heater going cold is related to the engine getting properly warm then the thermostat opening up & letting cold coolant from the radiator into the circuit? Before the thermostat opens you just have coolant circulating around the engine & heater, not the radiator. Maybe the thermostat is sticky & opening all at once? Very easy to remove & check a thermostat, & cheap to replace. You could also try going on a longer drive & find out if it starts blowing some warm air again as all the coolant gets up to temp.

Cheers
Clint

 

[MrWhiplash]

Hi
What vehicle exactly?
Either a) no or not sufficient amount of hot coolant is making it to or through the heater core any more (obstructed or clogged) or
b) the core doesn't exchange heat to air any more, which probably means the core is broken and lets the coolant take a straight in - out. In worst case, 'out' means out of the core onto the floor.
Let's go for the first thing first..
Check your floor / footwells: Any wet?
Check coolant level.
Check the heater main valve (Usually located in the engine bay on the firewall) Linkage OK and really fully open?
Check hose from engine to valve, with engine running & hot: Not kinked, being under pressure & hot?
Check return line from heater to engine. From cool: Drive truck warm, with heating off. Check return line temperature: Should be quite cool.
Now (engine running, still) turn heating on, blower off: Return line should become warm(er). If so, at least coolant makes it trough the core. Question then is: Is it sufficient volume and is it passing the exchange core or just passing straight through?
You can detach the heater circle from the engine and check by applying a controlled flow of liquid. If clogged, you should note.
If not any clogged or obstructed, the heater core is likely to be the culprit, I recon.
Good Luck Ralf

Yikes, can't believe I forgot the vehicle lol. 1993 LJ78. Thank you for the tips! I'll hop on checking these things out this weekend.

 

[Felde]

but it's weird that it works well initially.

Good point. I overlooked this.
Your assumption sounds reasonable. I can't imaging any other reason for an instant temperature drop, in particular if it always happens.
@MrWhiplash , do you have an accurate coolant temp gauge? If the effect @clintnz assumes really kicks in you should see it on the gauge, too. (The factory gauge may not be sensitive enough, though).
And, when extending the drive so all the coolant and radiator gets warm, the heater should come back to life, too.
Cheers Ralf