ViciousZ

iTrader: (1)

When exactly does the heater valve bypass the heater core? I assume it does it when the AC is running, but does it bypass the core anytime that the heat is not on, or when the lever is turned all the way to cold? I recently removed my AC, and I'm considering doing away with the heater valve, because IMO, it's clutter. But I'm afraid that the passenger compartment will get hot because of the coolant constantly running through it. Opinions?

Riley's35089rs+

I connected my heater box direct. I notice no change in the interior temp.

RB83L69

It doesn't "bypass" or "divert" anything. It's a gate: when the heater's temp setting is above the far left end, it gets vacuum and allows coolant to flow through the heater core. Just like a faucet.

It does slightly affect the interior temp, but not much at all. Lots of the earlier cars didn't have one at all, they had full-time coolant circulation through the heater core.

Damon

When set to Max A/C coolant gets bypassed so it doesn't go through the heater core.

You can confirm just by hooking up a vacuum gague to the vacuum line and then flipping the HVAC selector to different settings.

99Hawk120

That's interesting. GM must have set the system up differently on different cars!

On my 84 Olds, the vacuum line is keyed to the temperature slider. It blocks coolant whenever the lever is on "cold".

Damon

It wouldn't surprise me if they changed things around over the different models and years. They love to futz around with stuff that doesn't need futzing with.

99Hawk120

And personally, that setup (keyed to the temperature slider) makes more sense. I mean, do I want heat if I have the slider set on cold? Obviously not. This setup prevents the annoying hot air coming through the vents with the blower off, and the annoying "vent air always 5*-10* hotter than outside" problem.

Here's another interesting question: The divert valve in my Olds sits inline with the supply to the heater core and only has two ports (in and out). Yet, all the thirdgen valves I've seen have been three port. Is there something in the design of the coolant flow for the Small Block that requires the coolant to be able to route back to the block?

RB83L69

Don't the typical 3rd gen valves get hot water from both the front of the intake, and the rear; and have one "output" port to the heater core?

99Hawk120

I don't actually know, my thirdgen doesn't have one at ALL, and I haven't thoroughly analyzed the one in my friend's 92 RS...

ViciousZ

iTrader: (1)

I did a little research in my Helm/Chiltons/Haynes prior to posting the topic, and it didn't explain when the coolant was re-routed, or whatever it does. It did show the coolant pipe routing though. The coolant comes from the intake manifold into the valve. Then it goes #1: to the heater core, back out the heater core, and along a pipe that returns it to the radiator. Now that pipe has a T in it, and the #2 routing of the coolant is right out the valve, into that pipe, and presumably back to the radiator. I'm thinking it would clean up the engine bay by eliminating the valve, and the T in the pipe. My understanding was that any pre-87 car did not have the valve, so I'm guessing the pipe from the heater core won't have the T either.

I do know how to find out when coolant is 'diverted'. Put your thumb over the vacuum line while someone plays with the heater controls. Of course my car doesn't run right now, so I can't go check.

AJ_92RS

That's funny because I can set my A/C to Max and put the slider to hot and I get hot air. Huh?

Either you're mistaken on what you said, or you didn't tell all that's involved, or my car is special.

AJ

AFRO IROC Z

Yeah you do get hot air but, how about when you turn the defroster on and you put it on hot the a/c compressor comes on. A friend of mine told me becuase it helps take the moisture out of the air or something like that. If that is the case then you would get hot air with the a/c on and the slider over on hot, because i guess the heater thinks you want hot air on but you don't want moisture in the air. I am not sure really can someone clarify please, I would like to know also. Thank You.

RB83L69

Afro your friend is exactly right, you can use the A/C to dehumidify the air, and then heat it with the heater... works great on cold rainy nights and such occasions. It will keep the inside of your windows from fogging up like so many people you see driving around with when the weather is bad.

My 83 Z28 also differs from Damon's description. However, it varies from one car model to another. For instance, my 74 Caprice convertible's control system doesn't have a "max" position; but, when you put it in A/C and slide the temp all teh way cold, it goes to "Max" automatically... max fan, recirculate, no heat. That sucks because if there's one kind of car where the function described above is needed, it's a convertible.

ViciousZ

iTrader: (1)

Quote:

When set to Max A/C coolant gets bypassed so it doesn't go through the heater core.

You can confirm just by hooking up a vacuum gague to the vacuum line and then flipping the HVAC selector to different settings.

This is true. I went out and ran a test on my GTA, and there was only vacuum when the AC was turned to max. Meaning, I probably won't notice a difference in temperature in the car if I eliminate the T.

99Hawk120

So in effect, all we've proved is that GM is on crack. Again.

You would think they'd make up their damn minds about something so trivial, but noooo....

Don't even get me started on the 600 different ways they wired switches into the A/C clutch circuit. I think I've counted about 8 or 9 different ways on thirdgens ALONE.

Damon

Well, at least they got the big stuff right. I mean, how'd you like to drive a 302 Ford with only 4 head bolts per cylinder? At least GM put 5 in their small block (the number that G0d rightly intended a small block to have) so that you aren't tossing head gaskets anytime you lean on it hard! Heh heh.

No offense to the Ford contingent.

99Hawk120

Yes, they got the big stuff right, I'll give them that. That doesn't make the small stuff any less irritating