1967 Mustang With AC - Vintage Mustang Forums
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post #1 of 17 (permalink) Old 04-02-2019, 11:18 PM Thread Starter
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1967 Mustang With AC

I finished restoring the factory air in my car and everything went well considering most components were removed 25 years ago. But I have a question about the idle which drops too low with the AC on. Doing searches I see many cars had a part to compensate the drop in idle called by these different names,
idle speed control actuator
IAC
Idle stop solenoid
Idle control valve
Idle up solenoid
fast idle solenoid
SOLENOID FAST IDLE

What I haven't been able to determine is if there was ever on of these items on a 67 Mustang, It isn't the original carb but I still have the original and it only has a dashpot which didn't seem to do much when installed on the carb in the car now. Does anyone have any ideas on this? Thanks for any info.
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post #2 of 17 (permalink) Old 04-02-2019, 11:43 PM
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I think there was an idle compensater in the pcv line.
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post #3 of 17 (permalink) Old 04-02-2019, 11:54 PM
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Ford did not use an Idle solenoid on the Mustang in 67. Wouldn’t be hard to add one though.

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post #4 of 17 (permalink) Old 04-03-2019, 03:11 AM
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post #5 of 17 (permalink) Old 04-03-2019, 03:30 AM
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Quote:
Originally Posted by 289vert View Post
That looks like some thing Doc Brown made in Back To The Future III.
My son's 67 with factory AC we built does not have an idle compensator. Neither does my older son's factory AC '68. Or my daughter's '66 and my '65 with factory AC. We built all the kids cars from the ground up. Just set the idle a little higher then the normal RPM or find a way to use a solenoid on the carb linkage instead of the Doc Brown thing.

I know my '65 factory manual has specific instructions for setting the idle with AC. I'll need to check the '67 manual but suspect it will too.

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post #6 of 17 (permalink) Old 04-03-2019, 09:41 AM
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A few years ago I refurbished a one owner factory A/C "C" code coupe and it had that idle air compensator valve as shown and it did appear to function as intended. How effective it was over the long run is beyond my knowledge.

On the other hand, my "S" code fastback had been messed with by prior owners and that part was long gone when I bought the car. As far as fuel percolation I experienced that problem at 65 mph on a 104 degree day with A/C off. When the ambient temp dropped back down to 90 the fuel percolation was gone. I attribute that condition to the lower boiling point of ethanol in today's gasoline even though there are some here who would argue that ethanol infused gas does not have a lower boiling point.

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post #7 of 17 (permalink) Old 04-03-2019, 01:47 PM Thread Starter
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Thanks for all the answers.
I think there was probably an idle air compensator valve on my car at one time, I may hunt around and see if I still have it. It seems this valve was discontinued after a short while. I will try tinkering with the idle settings again but maybe because the engine is a little tired I may need to do some sort of mod. There are a lot of options out there using a 12v solenoid to bump up the idle when the AC is on but none are cheap and I was hoping someone might have done such a mode so I know which idle bump up would actually work. Too expensive to guess.
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post #8 of 17 (permalink) Old 04-03-2019, 02:09 PM
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Quote:
Originally Posted by Flade View Post
Ford did not use an Idle solenoid on the Mustang in 67. Wouldn’t be hard to add one though.
Um, he said compensator, not solenoid. And the early Mustangs (65-67) with AC did have a compensator. When underhood temps reached a certain level, the bimetallic, spliced into the PCV hose, would open the vacuum valve, reducing manifold vacuum, which sped up the idle, to cool the engine.


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post #9 of 17 (permalink) Old 04-03-2019, 02:13 PM
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Quote:
Originally Posted by 1965GTFB View Post
That looks like some thing Doc Brown made in Back To The Future III.
My son's 67 with factory AC we built does not have an idle compensator. Neither does my older son's factory AC '68. Or my daughter's '66 and my '65 with factory AC. We built all the kids cars from the ground up. Just set the idle a little higher then the normal RPM or find a way to use a solenoid on the carb linkage instead of the Doc Brown thing.

I know my '65 factory manual has specific instructions for setting the idle with AC. I'll need to check the '67 manual but suspect it will too.
In 1968, Ford switched to the Distributor Vacuum Control Valve, the little F-shaped dingus on the thermostat housing.

All of these valves were thrown away by teenagers in the 1970's because they thought they were "smog equipment that ruins horsepower".

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post #10 of 17 (permalink) Old 04-03-2019, 04:46 PM
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Um, he said compensator, not solenoid. And the early Mustangs (65-67) with AC did have a compensator. When underhood temps reached a certain level, the bimetallic, spliced into the PCV hose, would open the vacuum valve, reducing manifold vacuum, which sped up the idle, to cool the engine.

I was referring to the Original Poster's question

"idle speed control actuator
IAC
Idle stop solenoid
Idle control valve
Idle up solenoid
fast idle solenoid
SOLENOID FAST IDLE"

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post #11 of 17 (permalink) Old 04-03-2019, 05:40 PM
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As Flade said,it shouldn't be too hard to fit a solenoid spliced to the compressor wire.
But, I'm not sure that it needs it. I probably won't use one.
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post #12 of 17 (permalink) Old 04-03-2019, 05:58 PM Thread Starter
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As it turns out I have the remains of a idle compensator still in the car but it has been plugged with a bolt and is missing the important top part. Checking out the Distributor Vacuum Control Valve they used in 68 might work. My thermostat housing has a port for the valve.
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post #13 of 17 (permalink) Old 04-03-2019, 07:23 PM
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The temperature based vacuum switch used for idle control was used in 67 on A/C and thermactor equipped cars. If I recall there was a TSB as well. The use expanded in 68.

John
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post #14 of 17 (permalink) Old 05-12-2019, 03:55 PM Thread Starter
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Thumbs Up AC Low Idle Fix

I added a ported vacuum switch, which help a bit so I then added a Carburetor Idle Stop Solenoid. I am happy with the results, with AC on just a tap of the gas and the solenoid brings up the idle. With careful adjustment of the solenoid, the car idles exactly the same with AC on or off. Blowing 35 degrees out the vents after recharge with 2lbs of R12. I had to modify the solenoid bracket to make it work as well. Maybe others could use this info from a backyard car hacker.
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post #15 of 17 (permalink) Old 05-12-2019, 09:48 PM
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Quote:
Originally Posted by 1965GTFB View Post
That looks like some thing Doc Brown made in Back To The Future III.
My son's 67 with factory AC we built does not have an idle compensator. Neither does my older son's factory AC '68. Or my daughter's '66 and my '65 with factory AC. We built all the kids cars from the ground up. Just set the idle a little higher then the normal RPM or find a way to use a solenoid on the carb linkage instead of the Doc Brown thing.

I know my '65 factory manual has specific instructions for setting the idle with AC. I'll need to check the '67 manual but suspect it will too.
Factory AC cars should have one, but if it's a 4V engine it won't have the external HIC but a carburetor mounted one as shown on the following pix...

4100


4300


If you need a "throttle kicker" solenoid Holley and Edelbrock have specific kits for their carbs plus there are a number of "universal" solutions. These are wired in with your AC compressor clutch circuit and can also be switched by a power steering pressure switch.

Bart

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