Who makes the best AC thermostat for Carreras?

Jgordon · 08-04-2011, 09:19 AM

Have an 89 3.2, just had some AC work done. Diagnosis is a bad or weak thermostat. Understand that the OEM version is NLA.

Who makes the best replacement?

Thanks.

Barrpete · 09:47 AM

The one from our host works fine, you just have to modify the housing in the console a bit to fit it in.

You may also be able to simply the clean the contacts inside the switch. When mine went out a while ago I just opened it up cleaned out 25 years worth of lint and debris, shined up the contacts and that was all it took.

I'm assuming you mean the temperature switch.

Jgordon · 08-04-2011, 09:51 AM

Yes, that was my thesis as well. I have one coming from Griffiths (my car is in his care as we speak) but I was talking to him about potential failure points. It's a mechanical system, so assuming the gas hasn't escaped the system, it's likely just dirty contacts.

Will try cleaning (which has worked with most other systems thus far), and if that doesn't work, will try replacement.

Jgordon · 08-04-2011, 09:51 AM

Yes, the temperature switch (top left knob on center console).

mholbrook38 · mholbrook38's Garage

Can the switch be bypassed?

Barrpete · 08-04-2011, 10:51 AM

I'm sure the switch coming from Griffiths will be of good quality. It may even be from the same supplier, Ranco I think. Theres also a tech article on modifying the switch/housing to make it fit.

hcoles · 08-04-2011, 12:46 PM

I hope this is not too basic a question, I posted on another thread and copied here. I think this answers my question. The "left" knob is part of the temperature sensor/switch. I guess this signal is used to control the compressor clutch, right?

Another rookie AC question. The "temperature" knob on the AC control, how does this get colder or not so cold air to come out the vents? As I see it there is no external control of the TXV, only the compressor clutch and fan pushing the evaporator air or front condenser fan. If the compressor is on more the temp. in the condensers will be higher, means more heat is taken out and expands to a lower temperature in the evaporator. Is that how it works?

Barrpete · 08-04-2011, 01:06 PM

Quote:

Originally Posted by mholbrook38

Can the switch be bypassed?

Yes. It's just a set of contacts that open/close with evaporator temperature. Just connect the wires on the back. Should be a green & green with a white stripe. A word of caution though. Doing this will run your compressor continuously and after a while you can ice up the evaporator. Can eventually lead to damage to the compressor.

Barrpete · 08-04-2011, 01:20 PM

Quote:

Originally Posted by hcoles

I hope this is not too basic a question, I posted on another thread and copied here. I think this answers my question. The "left" knob is part of the temperature sensor/switch. I guess this signal is used to control the compressor clutch, right?

Another rookie AC question. The "temperature" knob on the AC control, how does this get colder or not so cold air to come out the vents? As I see it there is no external control of the TXV, only the compressor clutch and fan pushing the evaporator air or front condenser fan. If the compressor is on more the temp. in the condensers will be higher, means more heat is taken out and expands to a lower temperature in the evaporator. Is that how it works?

Yes the left knob is the temperature switch.

The way it works is that inside the switch is a bellows connected to a capillary tube that is inserted into the evaporator in the smugglers box. Open the smugglers box and you'll see what looks like a white wire. This tube is filled with a gas that expands/contacts as the temperature rises/drops. As the temperature in the evaporator drops the gas in the capillary tube contracts which in turn contracts the bellows and opens a set of contacts inside the switch disengaging the clutch at the compressor. With the compressor off the evaporator eventually warms up, the gas in the capillary tube expands, inflates the bellows, closes the contacts and the compressor kicks back in. Turning the knob to a lower temp means it just adjusts the point at which the contacts open so it will shut the compressor off at warmer evap temperature.

A long-winded explanation of a simple on/off switch.

hcoles · 08-04-2011, 01:26 PM

Barr,
Thanks for the complete explanation, makes perfect sense. Little by little I'm feeling better about my complete understanding of how the AC works.
-h

wwest · wwest's Garage

Quote:

Originally Posted by Jgordon

Have an 89 3.2, just had some AC work done. Diagnosis is a bad or weak thermostat. Understand that the OEM version is NLA.

Who makes the best replacement?

Thanks.

In what way, manner, is your thermostatic switch failing??

It's only BASE function is to prevent a freeze up of the evaporator when you have the setting FULL-ON. If your evaporator is still freezing up it may well be that the thermostatic switch's capillary tube/bulb is not inserted deeply enough into the evaporator core.