heater question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ironhead342001 · 12-02-2009, 10:13 PM

The heater in my '69 C-10 won't get very hot, barely better than luke warm. I've just put in a 195 degree thermostat and that didn't help. It has a 292 in it. It was 20 degrees here this morning so I could use some suggestions, thanks.

**Palf70Step** · 12-02-2009, 10:18 PM

My guess would be
1) bad/blocked heater core

2) Broken controller to switch to/adjust/increase the heat.

**425HP409** · 12-02-2009, 10:34 PM

First, make sure that the water pump is pumping. Take the small heater hose off of the heater core and start the engine momentarily to check for water pump operation. It should pump a full stream of coolant. If that is OK, take a water hose and back flush the heater core. Flush from the large hose through the small hose. That should give you plenty of heat if the blend door is allowing the air to pass through the heater core. Good Luck!!

ironhead342001 · 12-02-2009, 11:32 PM

thanks for the help guys. I replaced the heater switch on the dash and reworked all the cables and doors/flappers, so I think all that is working good. As far as the water pump, it should be good as well, she's my daily driver and she runs at 210 degrees all day long. I'll back flush the heater core tomorrow, hope that does the trick.

Andy4639 · 12-03-2009, 12:12 AM

Do you have a manual valve inline with the heater hoses by chance? Check the vacum valve as well. Check the heater box inside the truck once you get it up and running. The outer black surface should be warm if not you ant pumping through the core for some reason.
Make sure the cables didn't pop off the tit's and they are just moving back and forth without doing anything.

*highperf4x4* · 12-03-2009, 12:15 AM

.................. nevermind

andy beat me to it!

independentcustoms · 12-03-2009, 01:37 AM

I have a similar issue with mine. The truck itself doesn't get very warm, today I even blocked half of the radiator and I still can't get much heat into my engine.

Andy4639 · 12-03-2009, 04:30 AM

Check the thermastat see if it even has one. A lot of people take them out during the summer to let the motor stay coolier.

independentcustoms · 12-03-2009, 11:13 AM

Quote:

Originally Posted by Andy4639

Check the thermastat see if it even has one. A lot of people take them out during the summer to let the motor stay coolier.

I replaced it last week. I've been all through the heating system in the last week. Sometime before I bought the truck, a mouse had taken up residence in the heating system so I took it all apart and cleaned it all out. I just absolutely cannot get this thing to run warm, I can watch the temp gauge rise til the thermostat opens, then it drops way down.

*highperf4x4* · 12-03-2009, 11:31 AM

Then you have a thermostat issue. A tstat is intended to bring an engine up to optimum temperature as quickly as possible and keep it there to burn fuel more efficiently. If your engine is dropping back below the tstat temp then it's not closing like it should. You didn't install it upside down did ya? You will occasionally get one that is bad right out of the box. If you have a 190 in there, then the engine should stay at 190 or higher.

12-02-2009, 10:13 PM	#1
ironhead342001 Registered User Join Date: May 2009 Location: id Posts: 23	heater question The heater in my '69 C-10 won't get very hot, barely better than luke warm. I've just put in a 195 degree thermostat and that didn't help. It has a 292 in it. It was 20 degrees here this morning so I could use some suggestions, thanks. __________________ 67 C50 dump truck 69 C10 LWB 70 C30 72 K5 Blazer

12-02-2009, 10:18 PM	#2
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: heater question My guess would be 1) bad/blocked heater core 2) Broken controller to switch to/adjust/increase the heat. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! Last edited by Palf70Step; 12-02-2009 at 10:19 PM.

12-02-2009, 10:34 PM	#3
425HP409 425hp409 Join Date: Oct 2008 Location: Prosper Texas Posts: 841	Re: heater question First, make sure that the water pump is pumping. Take the small heater hose off of the heater core and start the engine momentarily to check for water pump operation. It should pump a full stream of coolant. If that is OK, take a water hose and back flush the heater core. Flush from the large hose through the small hose. That should give you plenty of heat if the blend door is allowing the air to pass through the heater core. Good Luck!! __________________ Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette

12-02-2009, 11:32 PM	#4
ironhead342001 Registered User Join Date: May 2009 Location: id Posts: 23	Re: heater question thanks for the help guys. I replaced the heater switch on the dash and reworked all the cables and doors/flappers, so I think all that is working good. As far as the water pump, it should be good as well, she's my daily driver and she runs at 210 degrees all day long. I'll back flush the heater core tomorrow, hope that does the trick. __________________ 67 C50 dump truck 69 C10 LWB 70 C30 72 K5 Blazer

12-03-2009, 12:12 AM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: heater question Do you have a manual valve inline with the heater hoses by chance? Check the vacum valve as well. Check the heater box inside the truck once you get it up and running. The outer black surface should be warm if not you ant pumping through the core for some reason. Make sure the cables didn't pop off the tit's and they are just moving back and forth without doing anything. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

12-03-2009, 12:15 AM	#6
highperf4x4 Account Suspended Join Date: Apr 2009 Location: Oklahoma City Posts: 4,709	Re: heater question .................. nevermind andy beat me to it! Last edited by highperf4x4; 12-03-2009 at 12:16 AM.

12-03-2009, 01:37 AM	#7
independentcustoms Registered User Join Date: Mar 2008 Location: Rochester NY Posts: 133	Re: heater question I have a similar issue with mine. The truck itself doesn't get very warm, today I even blocked half of the radiator and I still can't get much heat into my engine.

12-03-2009, 04:30 AM	#8
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: heater question Check the thermastat see if it even has one. A lot of people take them out during the summer to let the motor stay coolier. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

12-03-2009, 11:31 AM	#10
highperf4x4 Account Suspended Join Date: Apr 2009 Location: Oklahoma City Posts: 4,709	Re: heater question Then you have a thermostat issue. A tstat is intended to bring an engine up to optimum temperature as quickly as possible and keep it there to burn fuel more efficiently. If your engine is dropping back below the tstat temp then it's not closing like it should. You didn't install it upside down did ya? You will occasionally get one that is bad right out of the box. If you have a 190 in there, then the engine should stay at 190 or higher.



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