Need help--Armstrong TAC110

[bigric]

I'm helping a friend with his '70 Sovereign and we're working on the AC right now. It's got the TAC110-1 unit with the wall thermostat and no heat strip. The condensor fan works just fine, I believe I'm getting 24VAC at the transformer (it hums, and need to reverify it when I head back over today), but the compressor does not even attempt to come on. I can do auto AC and have never ventured into these types of units, but I've been reading this forum for hours and have picked up a few things.

Next steps for me include:
-verifying that we're on a 30A circuit
-verifying the transformer output voltage

Everybody seems to center on the start capacitor (the 25 uf one), and I'm good with that since I measured continuity across the terminals and no capacitance. I've also measured no capacitance on what I believe to be the run cap (the 43-53 Mf can with the resistor).

All that being said, I know that a few people on here have found modern equivalents for these parts, but I have yet to see the part numbers posted. For posterity's sake (and my own selfish reasons), could anybody post what they're using as replacements or what their research has turned up? Thanks for any and all help.

[nodpete]

Bigric-after you kill the power, take the cap off of the compressor & see if the electrical connecters are rusted. After sitting outside (probably) for 37 years it is possible that they are. Also, if the compressor is humming but doesn't start, wack it with a rubber mallet (I'm not kidding) it may just be stuck. If this is the problem, you can ad a booster to the start leg of the compressor.
nodpete

[bigric]

The connectors are in great shape. I'll try whacking it with a mallet.

Starter leg?

[lewster]

bigric,

If your meter measures capacitance, put one lead on the common terminal and get the microfarad readings from the others present. Also, this should be done with all of the terminals disconnected from the wiring.

Be careful about the possible charge stored in the caps. Before taking any readings, be sure that it is fully discharged. Put your meter on VAC and put the probes alternately across all of the terminals and you'll see the readings drop to almost nothing as you do this.

The rubber mallet trick might work if everything else is in good condition. Sometimes, the compressor just needs a 'little' shot to wake up.

[bigric]

Thanks for all of your help. We replaced the start capacitor then jumped the run relay and got it running. Now that all the HVAC stores are closed, I get to wait until Monday to get the new relay. On the upside, it blows incredibly cold. I'll post up the part numbers I used once I've got them all together. Thanks again.