75 Scottsdale heater problem

[Steve341]

It's about -20 Celsius or about 0 f today. Let the truck warm up real good. 30 mins. The heater only has defrost and floor heat. The air coming out is just warm enough to defrost the windshield at idle. It's Luke warm heat. So I get in it take it for a 10 mile drive and the heat stays the same. It's like wa and not hot. Temp gauge also does not move at all off cold while idling or driving. Is this a easy fix ? My other cars much newer heat gets hot to the touch. And temp gauges hover around half way. The truck has a 454 and no air conditioning. I plan on getting this vehicle registered and insured and it gets quite cold here in Edmonton Alberta Canada area lol. Need a heater that works properly. Thanks so much in advance.

[zieg85]

Sounds to me that you need a new thermostat with what you describe

[Steve341]

Hard to do? Cheap fix?

[Steve341]

Sorry forgot to mention fan only works on high as well

[zieg85]

Yes inexpensive to fix.  Follow the top radiator hose to where is connects to the intake manifold.  There is a housing that is held on by 2 9/16" headed bolts.  Under there is the thermostat.  Any auto parts store should have the thermostat and gasket...

[zieg85]

Fan is another story but usually it is the resister block that controls the different speeds.  http://www.autozone.com/autozone/parts/Duralast-A-C-Heater-Blower-Motor-Resistor/1975-Chevrolet-C20-3-4-ton-P-U-2WD/_/N-io8b8Z91tag?itemIdentifier=421165_399600_1678_6774 is what autozone shows to give you an idea

[Steve341]

Do I have to drain the coolant?

[VileZambonie]

You only need to drain enough coolant to be below the t-stat level but it's a good time to change our coolant while you're in there. Check your vacuum connection for the heater controls in the engine compartment as well so you have full functional control of the HVAC distribution.

[Steve341]

I broke the metal piece that holds the hose on the engine and I barely torqued it. I hope I can get the piece

[bd]

I broke the metal piece that holds the hose on the engine and I barely torqued it. I hope I can get the piece

Are you referring to the water outlet (aka, thermostat housing) pictured below?  They're readily available (the one pictured is just a random sample).

The thermostat may have slipped off to one side while you were tightening the bolts.  Or, you may have over-torqued one bolt before seating the other.

Make sure the manifold flange is clean, including the step-groove for the thermostat.  Make sure the bolt holes and bolt threads are clean.  Use a thin smear of silicone sealer on both sides of the T-stat gasket.  Apply the gasket to the water outlet.  Set the T-stat into place in its groove, set the water outlet with the gasket into place and support it firmly with one hand while you install the bolts.  Take the bolts down finger tight, only - then use your wrench to tighten each bolt a little at a time, moving back-and-forth between the bolts.  The bolts don't need to be overly tight, just enough to compress the gasket (15-20 lbs-ft).

[Steve341]

Yep. That's the piece. Stupid me torqued one sidefirst

[Steve341]

Well off to Edmonton I go this is costing more than it should have lol

[Steve341]

Thanks guys. Got heat. Let it run for 30 minutes while sitting in it watching temp. Got so hot in there I could barely stand it. The inlet I bought seems to leak. Not from the gasket but there is a half inch set screw in the top where as the stock one was sealed and a bit of bubbling coming out of there. Also temp on gauge is running just under half way between cold and hot. The neighbor I bought the truck from tells me the old big blocks have a summer and winter thermostat?

[84burb]

Thanks guys. Got heat. Let it run for 30 minutes while sitting in it watching temp. Got so hot in there I could barely stand it. The inlet I bought seems to leak. Not from the gasket but there is a half inch set screw in the top where as the stock one was sealed and a bit of bubbling coming out of there. Also temp on gauge is running just under half way between cold and hot. The neighbor I bought the truck from tells me the old big blocks have a summer and winter thermostat?

That is not a set screw. It is a plug with tapered pipe threads. You can try tightening it but I would recommend removing it and coating the threads with a hi temp silicone sealer or teflon tape. Reinstall it but don't over tighten it as you could crack your housing. You should be good to go.