the flyin' scotsman

can you post a pic of the compressor and belt

Mrmerlin

fix your fan first

griffiths

The stock compressor/crank/ belt alignment I recall is fixed, there is nothing to align.

"Rebuilt" compressor: you mean 'resealed' with case new o-rings and shaft seal? Did you check the steel cylinder
bores and piston's sealing rings? The condition of the the wobble plate and it half bearings?
All the thrust bearings and races are in order, the compressor turned freely by hand after you
put it back together? If so.... then most likely as suggested in the posts, if the belt tension was properly set, the upper hanging bolts tight, the belt tensioner is tight, then likely you are tossing the belt when the compressor locks up. It can lock up due to excessive pressures or lack of sufficient refrigerant and oil flow. If that persists then the compressor can wear apart quickly and toss debris through out the system: that would require a new compressor, new drier and liquid ac flush the lines, condenser and evaporator(s; tev's removed, if you have rear air you'd need to flush both sides of the rear solenoid).

Schocki

How hard or easy is it to turn the clutch disc of the compressor by hand?

When the car idles, how often does the compressor cycle?

griffiths

with the compressor out of the outer hub should turn easy,
the compressor does not 'cycle' like a orifice system, its a tev
system so the on/off is all relative to your temperature setting

Schocki

The electric clutch engages and disengages, I would call this cycling or am I wrong?

griffiths

Yes and no.
Your question was "at idle, how often".
If its 60F ambient vs. 90F its going to turn on and off less often.
If you have you windows open it will turn on and off more often.
Its all relative to the thermostat setting and heat gain.
There is no 'factory spec' or industry spec.

If it is 'cycling' very slowly, then we say it's got bradycardia.

Schocki

Ok, got it. Just wanted to know if it is running continously and with how much resistance...

Alan

This isn't how it works - it has nothing to do with the temperature setting - In AC mode it runs continuously - the only thing that cause it to cycle is the freeze switch (+ max pressure switch for factory config. R134a) - that's it. So when the ambient temperature is high/humidity is low it should never cycle.

Temperature control is always by mixing flaps directing airflow through/around the heater core (same mechanism as with heating only).

Alan

MBMB

I have fixed the fan and replaced the belt. I want to test to failure, but not far from my garage.

Assuming that the belt is jumping because the compressor is locked up when the clutch engages, which action is most likely to result in jumping?:

1. Start car with A/C on.
2. Switch A/C on at idle.
3. Switch A/C on at speed.

In other words, if I want the belt to jump, when should I switch the A/C on?

MBMB

It was rebuilt by a local (Houston) compressor rebuilder. I couldn't testify to what they did, but other than throwing a belt occasionally it works great.

j.kenzie@sbcglobal.net

Hi Mark,
Was your a/c system charged by weight? It should be 75-85% of R12 charge. If it is overcharged, you may go over pressure, and with no hi/lo pressure switch, you may lock up the compressor (or blow seals or hoses). I am in the process of refurbing my a/c, and I am putting in an Autohauz.az switch:
1 1248208310 AC High/Low Switch; Pressure Switch at Receiver Drier; 2 Spade Connector with Threaded Male Fitting 9.5mm
It is closed only within a normal running pressure range for r134. The exact pressures, I have forgotten. It is direct replacement for old switch and requires no new wiring.
Good luck,
Dave

Alan

It will occur most predictably when the ambient is hot, the radiator is already hot and the AC is up to pressure.

Worst case you can easily provoke is probably drive until full up to temp, high speed run to pre-heat engine. Turn on AC for a minute to get up to full pressure then slow down to slow speed in low gear so airflow over the condenser is heated by the radiator and cooled only by the fans with AC compressor still pumping well.

The stock R134a pressure switch is set to turn off at 32 bar (thats 464psi). With poorly operating fans it can hit that limit. Without the switch it will go higher - but your AC belt won't be happy well before that.

Needless to say it is easly to loose refrigerant if you are stressing the system like this - you might want to get a late model GTS R134a pressure switch - no additional connections to wire (high & low switches are combined) - not sure if the connector is the same...

Alan

MBMB

Thanks, Dave and Alan.

The low-pressure switch (959 613 137 00) and the pressure transmitter (928 606 150 00) are the same on the 87-91 PET as on the 92-95.

I may order a 1248208310 to install next time the system is empty.

Mrmerlin

before you fix the fans get a set of gauges on the system and see whats happening.
Then after the fans fixed retest it