1976 Thermal Valve(?) question for Heater

[24seven]

Howdy All,

I have a 1976 Riv(455)S/R and my question is about the heater. I replaced the core and hoses. The vent works well and blows hot and on "High". When I go to use the heater, it only blows low speed. The vent works in all ranges as does the AC. I replaced the resistor as well; no change.

I have a manual and it mentions some kind of "switch" at the back of the Passenger side head. Does anyone have a part number or source for this and/or name? It appears to screw into the block and has two electrical prongs on it. Will coolant leak out if I remove it, to show the parts guy?

RockAuto, Napa, Autozone have all said they don't stock it.

Thanks for any/all replies,

HenryJ ROA 11572 SoCal

[imported_75RivGS]

Do you mean this one? switch

[24seven]

Yes Rob!

Thanks so much. That is the part except that the

one on my car has two prongs like a houseplug.

I figured I might have to do the Ebay thing.

Do you think I would be able to adapt this somehow,

or should I just wait and hope another correct one shows

up?

Thanks Again, HenryJ ROA 11572 SoCal

[bob71GS]

Henry,

When I go to use the heater, it only blows low speed.

I think you are confusing the low speed blower relay with the temperature control switch.

The temperature control switch that screws into the right rear of the head is designed to allow the current to flow to the blower motor after the temperature reaches a certain temperature. This switch has nothing to do with the blower speeds.

There is a blower relay switch that is mounted on the firewall that controls your blower speeds. If your system is only working on the low speed, I would zero in on the blower relay switch. I've had to replace that switch many times over the years on my 71.

Bob Bonto ROA # 277

Technical Advisor 71-73

[imported_75RivGS]

I assumed the 76S/R had ACC (??):

[24seven]

Bob and Rob,

Thanks very much for the direction and manual scan. I see now which relay you speak of on the firewall. I will replace it and keep you posted. Thank you both, very much for the Info. I'll replace it and check back.

Thanks Again, HenryJ ROA 11572 SoCal

[24seven]

Well Folks,

It's been a while and I finally replaced the Blower Relay

as suggested, with no change. looking at the scan provided,

guess I'll do some back tracking. Again, all other Temp control ranges work. The A/C and Vent will respond to the toggle/slider arm to decrease and increase Blower speed. It's just the Heater function which only stays on the low setting and does not respond to Toggle/Slider arm movement.

Thanks for all the help again. HenryJ ROA 11572 SoCal

[imported_75RivGS]

I will try to find some more on trouble diagnosis and scan the pages later today