Where to get vacuum for heater valve on 87 Grand Wagoneer

[mantonas]

I've recently done a lot of work in the engine compartment of my 87 Grand Wagoneer, replacing the radiator, all the belts and hoses, and the carburetor, as well as removing most of the emissions stuff and simplifying the vacuum hose layout. I kept track of what was there and I have everything I need hooked up, except for one thing: the heater valve.

Somehow it escaped me that the vehicle had no heater valve; the previous owner must have removed it. I know what valve to buy and i know where to install it. But where do I get vacuum that is controlled by the A/C and heater controls?

The way I understand how the heater valve works is that as long as vacuum is pulling on it it's closed. I think that would mean that there is a vacuum valve somewhere that only restricts vacuum to the heater valve when the control module in the passenger compartment is set to A/C. Is this correct? Does anybody have any photos or a diagram of how this should be hooked up?

Thanks in advance for the help!

[Ristow]

no heater valve on these. theres a flap in the heater box,cable controlled,to regulate temp. there is also a vacuum controlled flap at the firewall to fully stop airflow.



the ac unit totally separate from the heater.





the controls on the dash will close the heater flap at the firewall when AC is selected.

[mantonas]

Thanks for the help but are you sure that applies to a 1987? All the auto parts websites list one for that year. Rockauto, Advance, Autozone, and O'Reilly list a Four Seasons 74612, and Napa lists one under their own part number that looks exactly the same.

I looked in my Haynes manual and it doesn't talk about one, which supports your position. Also, I looked under the hood of a friend's 1988 GW and it also doesn't have one, again supporting your position.

I'll be very happy if I don't need one because it saves me time and money, makes the heating system simpler, and reduces the potential for leaks.

[letank]

Thanks for the help but are you sure that applies to a 1987? All the auto parts websites list one for that year. Rockauto, Advance, Autozone, and O'Reilly list a Four Seasons 74612, and Napa lists one under their own part number that looks exactly the same.

I looked in my Haynes manual and it doesn't talk about one, which supports your position. Also, I looked under the hood of a friend's 1988 GW and it also doesn't have one, again supporting your position.

I'll be very happy if I don't need one because it saves me time and money, makes the heating system simpler, and reduces the potential for leaks.

Interesting, a lot of the parts catalog have errors/mistakes, no thermal valve,

[KaiserMan]

XJ's have a heater shut off valve. Are you looking up a 1987 Wagoneer or 1987 Grand Wagoneer? Wagoneer was an XJ after 1983.

[letank]

here is the vacuum ball on a typical FSJ with hoses for various outlets

[mantonas]

I'm sure that it was listed under Grand Wagoneer, not Wagoneer. The XJ Wagoneer would have had the bypass style heater valve. I'm familiar with the differences because I installed a 2 barrel intake from an 83 AMC Concord on a 76 AMC Pacer with a 258 inline six, and between 76 and 83 AMC went to a coolant-heated intake manifold which required a heater valve with a bypass, so that you could shut off the coolant to the heater core in the summer while still allowing it to circulate between the radiator and intake manifold. I think they used the same ones on 4.0 engines as well. The heater valve that they show for the Grand Wagoneer is a non-bypass type, like the ones used in old AMC inline sixes.

Anyway, you all have convinced me. No heater valve! Thanks!

[Bob Barry]

My '88 did not have the heater shutoff-valve in the heater-hoses; I added a bypass hose from the XJ, tapping into I-forget-which under-dash vacuum hose to operate it automatically (which you can do with the '86-up dash that has the integrated heater/AC controls). It helped keep the passenger-compartment cooler when I was running A/C.

[mantonas]

This seems like a good idea, to put in a valve that isolates the heater core whenever the A/C is on. However, is a bypass type valve necessary? For this engine, does the flow of coolant through the heater hoses perform any function other than delivering heat to the heater core? What if you used a non-bypass vacuum-operated shutoff valve instead?

[Ristow]

the V8 engines have a separate bypass to keep coolant moving with a closed thermostat,so no,the heater circuit is only for delivering heat.

[Bob Barry]

This seems like a good idea, to put in a valve that isolates the heater core whenever the A/C is on. However, is a bypass type valve necessary? For this engine, does the flow of coolant through the heater hoses perform any function other than delivering heat to the heater core? What if you used a non-bypass vacuum-operated shutoff valve instead?

Yeah, I forget my reasoning for using the XJ-style bypass valve, but it was cheap (if I recall; this was twenty years ago) and easy to integrate.