Manual/Electric heater core bypass on car with AC

[Rickard080TA]

I been thinking of getting an electric heater bypass like this one https://www.amazon.com/gp/product/B00LEUV98M?pf_rd_r=5ZA4WT0W2C7QE4HK5HQJ&pf_rd_p=5ae2c7f8-e0c6-4f35-9071-dc3240e894a8&pd_rd_r=a18daf4d-983d-415d-8bc0-e51260859a0d&pd_rd_w=kvQw2&pd_rd_wg=Pz55s&ref_=pd_gw_unk 
But when I went out and actually looked at the engine bay, I see that the whole AC blower and evaporator core just takes up a large amount of room where I would wanted to place the bypass. Now I have to think differently on how I want to do it. The old TransAmCountty had a great post about heater bypass which I bookmarked but is no longer valid. So has anyone add a controlled bypass on an AC car? I don't want to perm bypass it, just want my feet to stop burning in the summer. I eventually will fix the AC leak, but that aint happening until I fix this heating issue.

1980 TA w/ 301 (non-turbo) AC car.

[Jeremy]

I just put a manual shutoff on my son's 79 camaro.  It is a 3/4 pex ball valve.  The places for the hoses measure perfectly 5/8 inch.  It is very small and I was able to mostly hide it.

It helped me get the interior vent temps down.  Center vents went from 50 ish at idle to 37 at idle and 33 going down the highway.  All I did was install the block off and adjust the pressure slightly.

I looked at making a bypass but it made the plumbing more complicated in my mind.

[81Blackbird]

That is exactly what I did.  I placed the handle down and painted the brass black.  I took the handle off because it is unsightly and keep it in the console.  When late fall or winter comes around I open it up. Spring and Summer I close it.  $10 and 15 min.

https://www.homedepot.com/p/Homewerks-Worldwide-3-4-in-Brass-PEX-Barb-x-PEX-Barb-Ball-Valve-Lead-Free-111-5-34-34/312480622#overlay

[81Blackbird]

Jeremy,  what is your setup the you get such low temps?

[b_hill_86]

I probably over complicated my setup but I used a vacuum operated valve attached to an electric vacuum solenoid wired to a small switch under the dash. The valve is open at rest and the solenoid is closed at rest. So, switch off, no vacuum = valve is open. Or if either piece fails it should cause the valve to remain open which is what I wanted. Flip the switch, solenoid opens and provides vacuum which closes the valve. It seems to help and would be easy to wire into the AC controls if you wanted. One thing I added was a check valve on the vacuum line to prevent loss of vacuum at heavy acceleration from allowing the valve to open. Not sure how well that works.

I would just assume try the manual ball valve in the future for simplicity too though.

[scarebird]

My Vintage Air setup came with a single electric ball valve, but a manual unit will work fine - only need to block one hose.

[Wallington]

As easy as installing a vacuum heater tap that taps into the vacuum controls of the AC controls.

[NOT A TA]

Early 2nd gens had a vacuum operated valve on the passenger inner fender. They're controlled by the HVAC mechanisms.

[FormTA]

So, you only need to block one line? You don't need to send the fkow back to the inlet of the water pump? Mine may be different as it is an LS engine though.

[Wallington]

In the case of an LS I'd be using the original heater tap to suit that vehicle, usually vacuum-controlled also, rigged off the factory control unit that redirects vacuum under different settings and whatever suits.

[Rickard080TA]

Jeremy, 81Blackbird, do either of you have pictures of how it turned out?

b_hill_86, that sounds like what I want to do but electrical I figured would have been easier, but do you have pictures of your setup?

[firebirdparts]

So, you only need to block one line? You don't need to send the fkow back to the inlet of the water pump? Mine may be different as it is an LS engine though.

We had a lengthy debate about this.  I say no.  On the original setup, the heater core bypasses the cylinder head.  So it would be better, I think, to block the flow.  That would force more water through the cylinder heads.  not sure how your is piped up, though.

[JJ 109]

Yes you have to be careful. Some engine circuits you cannot shut off, you have to create a bypass to complete the circuit. My LS is this way.

[81Blackbird]

Needs to be touched up but you get the idea.

[b_hill_86]

This is the best picture I have on my phone. I can take more if you’d like but it won’t be till I’m back home Sunday. It’s the two brass looking items

[Rickard080TA]

This is the best picture I have on my phone. I can take more if you’d like but it won’t be till I’m back home Sunday. It’s the two brass looking items

I would like a few more pictures, please and thank you. Have a safe trip back home.

Need to be touched up but you go the idea.

If I go the simple way, this looks very clean, Thanks.

[b_hill_86]

This is the best picture I have on my phone. I can take more if you’d like but it won’t be till I’m back home Sunday. It’s the two brass looking items

I would like a few more pictures, please and thank you. Have a safe trip back home.

Need to be touched up but you go the idea.

If I go the simple way, this looks very clean, Thanks.

No problem. I will set a reminder in my phone.

[Jack]

I have a simple old school valve (plastic knob that's barley noticeable), I'll post a pic.

[cyber104]

Jeremy,  what is your setup the you get such low temps?

I'm VERY skeptical of 33 degrees.  Even the very best R12 systems don't get below 37 - but he also didn't mention outside temperature - I guess if the outside temp was low enough you could see that.

Mine is in great shape with the proper charge and I'm getting 38 @ 93F on the highway.

I also have a manual bypass (shutoff) valve in the engine compartment.

[b_hill_86]

I’m not sure if you want some other type of picture but I took these two tonight. One is of the vacuum operated valve and the other is the vacuum solenoid. Fairly I expensive parts I got on Amazon I believe. A ball valve would probably work just as well but curiosity got the better of me and I wanted to see if I could get this to work.

[Wallington]

I'm VERY skeptical of 33 degrees.
[/quote]

I had my R-134a blowing 38 at the vents while idling during gassing up, but it would start to freeze up, Then cut out, had to wait for it to warm up and melt at the switch before it would come back on. Even had to tap the switch a few times to trigger it again. Had to bump it back another degree or two. Untested on the road where it would be different. It would be much more efficient at cooling if you could get a constant use out of it at slightly warmer level, rather than cycle and off for several minutes to defrost, while cabin warms up again. But then the pressure leaked so it's all practice.

[Rickard080TA]

I’m not sure if you want some other type of picture but I took these two tonight. One is of the vacuum operated valve and the other is the vacuum solenoid. Fairly I expensive parts I got on Amazon I believe. A ball valve would probably work just as well but curiosity got the better of me and I wanted to see if I could get this to work.

Thanks. So if you turn the AC on, it blocks the valve? So if you are just running without AC then the heater core is getting hot coolant? If correct, then that is not what I ultimately want, but like what you did. I want it more like this:
Car off = valve open, coolant flowing
Car running = summer and valve is closed, winter and valve is open.
Car running with AC = valve closed, no coolant.

So it looks like mechanical or electrical is what I want.  I started looking at electric, which might be the best, but then I saw the mechanical one at a car show over the weekend. I already have a manual choke cable that is not connected to the choke that I might be able to use. I have never noticed them before but must have seen tons of them at the NSRA show.

Now my next question would be which hose do I put the valve on. Do I put it on the side before going to the Heater core, or after. I would assume before.

[Wallington]

You already have vacuum-control for various vents and recirculation, tap into one of those so the setting either opens or closes the heater hose tap to suit.

[b_hill_86]

I’m not sure if you want some other type of picture but I took these two tonight. One is of the vacuum operated valve and the other is the vacuum solenoid. Fairly I expensive parts I got on Amazon I believe. A ball valve would probably work just as well but curiosity got the better of me and I wanted to see if I could get this to work.

Thanks. So if you turn the AC on, it blocks the valve? So if you are just running without AC then the heater core is getting hot coolant? If correct, then that is not what I ultimately want, but like what you did. I want it more like this:
Car off = valve open, coolant flowing
Car running = summer and valve is closed, winter and valve is open.
Car running with AC = valve closed, no coolant.

No, mine is not tied into the AC controls but it could be easily if that’s what someone wanted. Either tap into the idle solenoid or the compressor power before the pressure switch.

Mine is activated by a small switch under the dash I didn’t picture but it functions somewhat like you said.

Car off, no power, no vacuum, valve open. Coolant flows.

Car on, switch on provides vacuum to the valve which closes it. No coolant flow.

Car on, switch off = no vacuum to the valve and the valve remains open at rest. It could be configured the opposite by use of an open-at-rest vacuum solenoid but I wanted it so that if any part failed for some reason it would fail in a way that will allow coolant to flow.

Mine is installed between the head and the heater core. I also added a check valve so when there is a vacuum drop under acceleration the valve doesn’t open. I’m not sure the particular check valve I have works perfectly but I think it helps.

[Rickard080TA]

I’m not sure if you want some other type of picture but I took these two tonight. One is of the vacuum operated valve and the other is the vacuum solenoid. Fairly I expensive parts I got on Amazon I believe. A ball valve would probably work just as well but curiosity got the better of me and I wanted to see if I could get this to work.

Thanks. So if you turn the AC on, it blocks the valve? So if you are just running without AC then the heater core is getting hot coolant? If correct, then that is not what I ultimately want, but like what you did. I want it more like this:
Car off = valve open, coolant flowing
Car running = summer and valve is closed, winter and valve is open.
Car running with AC = valve closed, no coolant.

No, mine is not tied into the AC controls but it could be easily if that’s what someone wanted. Either tap into the idle solenoid or the compressor power before the pressure switch.

Mine is activated by a small switch under the dash I didn’t picture but it functions somewhat like you said.

Car off, no power, no vacuum, valve open. Coolant flows.

Car on, switch on provides vacuum to the valve which closes it. No coolant flow.

Car on, switch off = no vacuum to the valve and the valve remains open at rest. It could be configured the opposite by use of an open-at-rest vacuum solenoid but I wanted it so that if any part failed for some reason it would fail in a way that will allow coolant to flow.

Mine is installed between the head and the heater core. I also added a check valve so when there is a vacuum drop under acceleration the valve doesn’t open. I’m not sure the particular check valve I have works perfectly but I think it helps.

Ah, it is much clearer now. That would be what I want. Especially the fail open feature, didn't really think of that. I know it sounds overly complex compared to just a single throw manual valve, but this has peaked my curiosity.  Do you have part numbers for what you put in? I think this would be a great mod to do.

[b_hill_86]

I ordered them both from Amazon then the toggle was just a parts store buy

Universal Air Conditioner SW 9001C A/C Solenoid Valve https://www.amazon.com/dp/B003R43J2C/ref=cm_sw_r_cp_api_glt_fabc_4424DD1M4EMXDEB5Y2D3?_encoding=UTF8&psc=1

Universal Air Conditioner HV 1022C HVAC Heater Control Valve https://www.amazon.com/dp/B003R33QZS/ref=cm_sw_r_cp_api_glt_fabc_610M6THRH24PDK3M3R87?_encoding=UTF8&psc=1

[Jeremy]

I though the 33 was a little colder than expected.  I used an infrared thermometer from harbor freight for testing.  My 94 Firehawk shows 31-32 at the center vents and my 18 silverado shows 30 for comparison so the gauge may be a little cold.

I used it to test the temps at the center vents on max AC.  I knew the system was low on charge and bringing it up to the desired low side of the pressure range on the gauge that you can get with the cans of Freon got it performing better.

I then used the infrared thermometer to set the pressure.  I'd slowly add freon and wait for a reading on the thermometer.  I kept slowly adding freon until I got no change in the vent temp.  It ended up showing lower then the ideal pressure on the gauge for the outside temp.

Car is a stock 79 camaro with a 305 with only a conversion to R134.

Hope that clears up the confusion on testing methods.  In a nutshell, being meticulous with the charge and adding the block off, got the old system within 2-3 degrees of much more modern AC's.  I know it works as my wife has ridden in it several times with AC and never complains of getting hot.  Black on Black car so it works if the wife is happy.