The Stovebolt Site Forums The Shop Area General Truck Talk single switch heater

Hello, With a 1959 GMC 100 and the heater fan and core assembly were not installed when I bought it. I've taken the heater core to a local shop and they are fixing the leak. They called and asked about some kind of additional valve that I should bring in and they'd weld on as part of the rebuild. The core seems to just fit into the sheetmetal box it's held in so I wonder what it could be. This heater seems super simple. One single control knob on the dash. The heater core has two copper tubes stubs coming out of it that look they'll run nicely through the 2 hole up under the dash on the passenger side where the unit hangs. I have the repair manual and it seems to have no reference to any heaters. Anybody no where I might find a diagram of the 1959 GMC heaters?

I Have a 59 chevy and have the basic heater, one switch for the fan. There is an upgraded heater that functions like a modern heater in a car, that you can adjust the temp. There is a valve called a ranco valve. Your heater doesn't have that valve. That is probably what the shop is talking about. On the other hand they may be talking about a shut off valve, but that is not connected to the core , it is inline from the water pump to the heater core.

danP is your core round ? If so that is the simplest heater was recirculate full time,had a lever for defrost.

Thanks Tommy, that seems right. No- my core is rectangular. The dashboard knob feels like it has a couple of detents as I turn it but I think it's just a simple on off switch.

danP you can find more on installation of heaters in the 'Accessories Installation Manual'.. Many of these trucks came stock with no heater & in owner wanted one, they would have them installed at dealer..
delky dave in WYo

Thanks for the advice about the Accessories Installation Manual. I can't seem to locate a GMC version. Is the Chevy accessories installation manual the thing I seek?

As said: economy has no temp control, no valve and is recirculating only. Deluxe has temp control and is recirc or fresh air.
The deluxe has a adaption to the passenger air vent for fresh air inlet.

So plumb in, and wire, whichever one you have and and you are done.

Right on Bartamos- Thanks. My unit looks a bit different, but still the same simple Simon type. The sheet metal diverter portion says "Harrison". The heater hasn't ben installed on the truck since long before I owned it. I just had the leaking core restored. I was thrilled when I looked up under the dash and saw the flexible pipes leading to the defrost vents tucked up there. The one thing I'm not certain about is if there should be some kind of valve in the set up to stop the continuous flow of liquid though the heater core. Right now the two heater hoses are joined together with a hose barb under the hood. It looks like they just connect up to the naked copper end pipes of the heater core that will be poking through the fire wall. The heating "module" on the dash is a single button that seems like it will be the on off for the fan connected to the heater core box. I'm thinking the heat will simple radiate into the passenger compartment non stop with out some kind of physical disconnect valve to stop the water circulation.

I was editing when you posted just now. Please re-read for final info.
This style is the cable version.....and any plumbing supply place will have the handle version. or FLAPS.Both mounted outside the fire wall.

Joining the hoses together works also and eliminates any possible inside cab leaks. Not that hard to switch over.

Harrison was the supplier to GM for heaters, radiators..........
.
Don't know what this is or what you mean until I see a pic or three. "The heating "module" on the dash is a single button that seems like it will be the on off for the fan connected to the heater core box."

What version of the two types of heaters, I posted, do you have?

I show the heater in the picture here. The 2 copper pipes that look like they'll run through the fire wall holes shown under the battery tray. The picture showing the firewall shows the heater hoses just connected together with a pipe near the two firewall holes. The fellow at the radiator shop that rehabbed the heater core said there may be a valve of some kind that would be attached to this core.

55-59 GMC Heater Seems like you have the same Recirc style. Tell your builder, no valve.
Looks pretty similar to 60-66.
The ebay pic shows a 53-54 GMC logo. There is no 55-59 available.

Good eye you have there paramos. Thanks for the link it showed I'll need a few bushings for the mounting bolts. It looks like this unit will radiate some heat all season regardless of the fan blower being on or not. Might have to install for the cold fall season and remove it again next summer.

Just put a manual shut off valve in the inbound heater hose under the hood. Google heater shut off valve then go pick one up at your local FLAPS.

Yikes. Common sense tells me to install a diverter valve under the hood between inlet/outlet lines so you don’t have hot water circulating all summer. I suppose that’s against the rules for a show vehicle being judged on originality though.

Wouldn’t it be better to keep the fluid flowing through both lines under the hood?

I actually have a shut off valve on each heater hose (po did it that way), and have had no problems at all so far. It is 49 degrees here this morning so I guess it is time to open them up.
Lee.

I like the under hood diverter ideas but that's been my question-I figure I'll have to install a valve that allows the coolant to keep flowing through the heater hoses while isolating the flow to the heater core. I show a picture of my in-dash switch here too. It feels like there might be two detents when you turn it.

1. You are not looking for a diverter, you use a simple shut off valve on one of the hoses, as I previously linked you to, and explained. At post 1428844
2. Your heater probably has a two speed motor, hence two positions CW from off.
3. Who is paramos ?
4. The best valve to use is a ball valve, rated for hot water and with the correct inlet/outlet size.

I see now- I skipped right past that dang post somehow and missed it. bunked up your name spelling there too and put salt in the wound. Great tips!