After market A/C clutch

jayvee34

jayvee34

Senior Member
1968 Mercury Cougar with custom fit A/C Unit. When the A/C unit is turned on
(fan switch on low, temp switch to max cool) and the compressor clutch is activated the volt gauge drops from 14.30volts to 12.7volts, fan switch to high,
voltage drops to 11.7volts. New 100 amp Motor Craft alternators output is
14.30volts @ 1,000 RPM's.

I checked the above voltage reading with a Multi Meter, and they read with-in
a 1/4 of a volt as the volt gauge.

Could anyone here have a idea or know what could be my problem
Thanks for any help, John
 
So you put an aftermarket kit in the car? Can you tell us the vendor and compressor manufacturer?

Did the clutch assy come mounted on the compressor or did you have to mount??
 
KULTULZ said:
So you put an aftermarket kit in the car? Can you tell us the vendor and compressor manufacturer?

Did the clutch assy come mounted on the compressor or did you have to mount??
Click to expand...

Old Air Products, came as a kit, including the compressor with the clutch
mounted.

Might add that it was installed several years ago. At that time it had a idiot light for the
battery charging. Has a volt gauge now.
 
At what RPM are you taking the voltage readings? If at 1000 you are looking at fairly normal drops, try doing it at 1500 and post the results.
 
Ford blue blood said:
At what RPM are you taking the voltage readings? If at 1000 you are looking at fairly normal drops, try doing it at 1500 and post the results.
Click to expand...

There you go, first step. Is the ALT true MOTORCRAFT or an aftermarket rebuild? Plot a charging graph at different engine speeds. Maybe full field the ALT to also check output. BAT is in good condition and all wiring good?

Did the instructions give an AMP draw for the clutch? Have you performed a AMP draw test on the blower motor?

It may be that you will have to go to a feed directly off the BAT via a relay and fuse.

It never triggered the AMP LAMP before the VOLTMETER INSTALL?
 
Ford blue blood said:
At what RPM are you taking the voltage readings? If at 1000 you are looking at fairly normal drops, try doing it at 1500 and post the results.
Click to expand...

@ 1500 RPM the voltage drop is about the same at low fan speed, at high fan speed voltage is at 12.7, high fan and lights on drops to 12 even.
 
KULTULZ said:
There you go, first step. Is the ALT true MOTORCRAFT or an aftermarket rebuild? Plot a charging graph at different engine speeds. Maybe full field the ALT to also check output. BAT is in good condition and all wiring good?

Did the instructions give an AMP draw for the clutch? Have you performed a AMP draw test on the blower motor?

It may be that you will have to go to a feed directly off the BAT via a relay and fuse.

It never triggered the AMP LAMP before the VOLTMETER INSTALL?
Click to expand...

Don't have a amp meter, idiot light did flicker. Alternator is a after market
rebuild Motor Craft. I will install a 40 amp relay and report back.
Thanks very much Ford Blue Oval, and KULTULZ.

Oh, KULTULZ, Knew of a person's location in Mio, Mi.
 
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jayvee34 said:
I will install a 40 amp relay and report back.
Click to expand...

... hold on ...

You need to know if the ALT is alternating properly and AMP draw of the clutch and blower motor (voltage drop test).

Did the install instructions give you any specifications such as AMP draw of the clutch? It also may be a bad component in the clutch. Does the clutch receive full BAT VOLT when cut on?
 
KULTULZ said:
... hold on ...

You need to know if the ALT is alternating properly and AMP draw of the clutch and blower motor (voltage drop test).

Does the clutch receive full BAT VOLT when cut on?
Click to expand...

I will have to get a amp meter, and will also check if the clutch is getting full
voltage when turn on. Report back later, thanks again.
 
I hope to have found the problem. The alternator started acting radical.
Volts up then decrease, add a load and really decrease.
Got a new alternator. Will report back tomorrow.
I do have a Multi Meter.
 
jayvee34 said:
I hope to have found the problem. The alternator started acting radical. Volts up then decrease, add a load and really decrease.

Got a new alternator. Will report back tomorrow.

I do have a Multi Meter.
Click to expand...

The multi-meter should have an AMP gauge.

You should also replace the VOLTAGE REGULATOR as a matter of fact. I suggest finding a MOTORCRAFT and not off-shore.

This is a 100A 1G ALT w remote VR?
 
One of my meters has a 10 Amp meter, the other is only Volt/Ohm.
I did replace the regular with one that has short protection.
yep, 100A 1G alternator with side connections. This alternator is
about 1 1/2 times larger than the regular size alternator in diameter.
Photo's attached.
 

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Installed the new Alternator and everything seems good to go. Engine at idle 14.28V,
engine at idle lights and emergency flashers on 14.25V. engine at Idle A/C on 13.6V.
BTW. Picture of the alternator is the old one, just wanted to show what it looked like.

Thanks and best wishes for all the help.
 
I’m glad its working, but one more thing you might look at. I doubt the oem wiring was for a 100 amp alternator. You load it up enough to use that kind of amperage continuous, something in the middle is going to melt. Or burn.

Most alternators in those days were 30-40 amps. #10 wire. 100 amps is #2. When I upgraded the alternator in my bird for the a/c and condenser fan I had to rewire from the alternator to the battery to carry the additional output.
 
jayvee34 said:
I did replace the regular with one that has short protection.
yep, 100A 1G alternator with side connections. This alternator is about 1 1/2 times larger than the regular size alternator in diameter.

486501
Click to expand...

What application did you remove/buy this ALT for? It does have an external VR?

Can you show a photo installed?

THANX!
 
miker98038 said:
i’m glad its working, but one more thing you might look at. I doubt the oem wiring was for a 100 amp alternator. You load it up enough to use that kind of amperage continuous, something in the middle is going to melt. Or burn.

Most alternators in those days were 30-40 amps. #10 wire. 100 amps is #2. When i upgraded the alternator in my bird for the a/c and condenser fan i had to rewire from the alternator to the battery to carry the additional output.
Click to expand...

Very Important Info!
 

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Thanks, I did consider that and wired from the starter solenoid to the alternator
with a 6 ga. wire. Also today I plan to rewire the a/c switch to the blower motor,
and the wiring to the binary switch to the a/c clutch with #12 wire.

I don't know what a VR is.

OOps,
this old brain is not working swiftly this morning. I did replace the Voltage regulator
at the same time I replace the Alternator. The original alternator was the standard
G1 with external VR. (I believe to be a 45Amp Alt).
 
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