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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: mikewb on December 17, 2007, 05:41:08 pm

Title: Heat
Post by: mikewb on December 17, 2007, 05:41:08 pm

my heater wont blow warm. stays cold. any suggestions?

Title: Re: Heat
Post by: Captkaos on December 17, 2007, 05:53:26 pm

Is it leaking?  Do you have A/C or just a heater?  Are the doors functioning properly?  Are there hoses going to the core?

Title: Re: Heat
Post by: mikewb on December 17, 2007, 07:57:04 pm

it has a/c too but not charged. the hoses are hooked up . it blows but never warm i think motor may not be gettin warm enough

Title: Re: Heat
Post by: 78ScottsdaleK20 on December 17, 2007, 08:12:34 pm

Just a suggestion that I had experience with...

I too had only warm air coming through, never would get hot. The heater temp control lever would not go all the way over to the right. So I had to remove the main heating duct near the heater core and found a bunch of 30 year old accumulation of crud and things dropped in their blocking the door from opening and shutting completely. Try checking there.

Check and ensure all your heater hoses are good and they are getting the necessary coolant flow to the heater core.

Could also try a different temp thermostat.

Title: Re: Heat
Post by: JJSZABO on December 18, 2007, 08:43:57 am

Check for mice or mouse nest in your heater duct.  Little rodents get into everything.  This is an easy check before having to replace your heater core.

Title: Re: Heat
Post by: zieg85 on December 18, 2007, 09:05:49 am

A couple of other things to look at:  Compare the 2 heater hoses temp.  If the core is nearing plugged one will be colder than the other.  If they are just luke warm chances are your thermostat needs changing. 

Title: Re: Heat
Post by: mikewb on December 18, 2007, 03:06:00 pm

the motor barely comes off cold i think thats it

Title: Re: Heat
Post by: jonkmbll89 on December 18, 2007, 08:06:15 pm

If your motor barely comes off of cold than you should try a higher thermstat.

Title: Re: Heat
Post by: mikewb on December 18, 2007, 08:55:49 pm

what size is stock and what is biggest

Title: Re: Heat
Post by: eventhorizon66 on December 18, 2007, 10:21:29 pm

195* should be the stock temp rating, thats what I'm running.  The lowest you can get is a 160*, I think.  It's probably just a stock thermostat that's stuck in the open position.

Title: Re: Heat
Post by: Lt.Del on December 18, 2007, 10:40:46 pm

I second the tip on checking both hoses going into the firewall.


That will tell you what's going on.  If just a little warm, both, then it IS your engine temp.

If one is hot, the other is not, you have a clog in the hose or heater core.

If both are hot and still no heat inside, your core may be at fault or the heater flaps (doors) or controls are bad.

Both hoses should be pretty darn hot.