What is this called?

[Dobalovr]

Ok guys I have been through the FSM the Parts Data Book on my 79 300 and I can not find the name or part number of this switch on my intake. I thought it might be the low pressure switch but I have one mounted on my evap valve already. It is AC related so I am left with High pressure switch or clutch cycling switch. E58 360

What is it?

 

[azblackhemi]

Isn't it the temperature sending unit?

 

[Dobalovr]

Isn't it the temperature sending unit?

The temp sensor for the guage is different so is this a temp sensor for the ac system?

 

[Davea Lux]

That is a water temp switch, I am pretty sure they used this type of switch to disable the compressor from running until the engine reached operating temps so that the evaporator would be less likely to ice up in defrost mode. Been a long time since I have seen one of those. Also might have been used to disable the blower until there was enough heat to provide defrost. Does this car have ATC2?

Dave

 

[saforwardlook]

Given its appearance and location, it is a coolant temperature switch. It is the same one used in fuselage Chryslers for example for the hot/cold lights. Dobalovr, you should have one in your 1970 Chrysler 300. GM used them commonly as well in those times.

 

[CBODY67]

1979 "Cordoba" 300 would have had a temp gauge, not a temp light. As my '80 Newport has a gauge with the LED indicator light. The ambient air temp sensor for the a/c compressor disable (below 32 degrees F, or thereabouts) is elsewhere in the hvac system, not on the engine.

Might be a CCIE switch sensor? Coolant Controlled Idle Enrichment sensor, which worked a solenoid on the TQuad. An emissions item. Have to do some checking as my those memory archives haven't been opened in quite a while.

CBODY67

 

[Ross Wooldridge]

Two prong temp sensor connection for use with a hot and cold light setup typically found in Chryslers. Dodges and Plymouths had guages, and hence a different sensor and connector.

 

[Davea Lux]

1979 "Cordoba" 300 would have had a temp gauge, not a temp light. As my '80 Newport has a gauge with the LED indicator light. The ambient air temp sensor for the a/c compressor disable (below 32 degrees F, or thereabouts) is elsewhere in the hvac system, not on the engine.

Might be a CCIE switch sensor? Coolant Controlled Idle Enrichment sensor, which worked a solenoid on the TQuad. An emissions item. Have to do some checking as my those memory archives haven't been opened in quite a while.

CBODY67

The ambient temperature switch on ATC2 systems should be under the dash. I am wondering if this switch is for the lean burn system as that shows on the lean burn wiring diagram. The confusing part though is it looks like the lean burn temp switch might be a single wire type. Can't remember if the non ATC systems used an ambient temp switch or not, I am thinking that they probably did by '79 so this could be for that purpose also. I have attached a diagram if the lean burn temp switch wiring diagram. Click on mail 123pdf.

Dave

 

[CBODY67]

1979 RWSX (B-platform) cars didn't have any ATC a/c systems. By that time, too, ELB was replaced by Electronic Spark Control. Almost all of the emission control system was run by vacuum via thermo-vacuum switches rather than electricity. As the engine was the "ground", a two-wire situation would either mean it was a dual-function sensor or a more direct/reliable circuit was needed, so the sensor was "ungrounded", using a + and - wire instead. Have to do more searching.

CBODY67

 

[Dobalovr]

1979 "Cordoba" 300 would have had a temp gauge, not a temp light. As my '80 Newport has a gauge with the LED indicator light. The ambient air temp sensor for the a/c compressor disable (below 32 degrees F, or thereabouts) is elsewhere in the hvac system, not on the engine.

Might be a CCIE switch sensor? Coolant Controlled Idle Enrichment sensor, which worked a solenoid on the TQuad. An emissions item. Have to do some checking as my those memory archives haven't been opened in quite a while.

CBODY67

That just may be it. It is definitely measuring coolant temp on the intake. It is bundled together with the water temp guage wiring and the iflle stop solenoid wiring (Tquad is long gone) in the harnesd. I was thinking high pressure limit switch which appears on police versions in the FSM. I have blocked off the vacuum switches that were part of the ELB.

Thanks for the help everyone keep the ideas coming. I just thought someone here might have replaced it on a small block with AC in the past as I am in the Great White North I don’t work on too many AC cars. Thus is my first actually....

 

[Davea Lux]

The police version high pressure limit switch is to cut out the compressor if the car is in a high RPM operating mode so that the compressor does not self destruct (Some models had a toggle switch added on the dash as part of the police equipment package to disable the compressor on high speed chases). The pressure switch is not attached to the cooling system, but on the high pressure line from the compressor.

Dave

 

[CBODY67]

OR . . . should the a/c system "head pressure" exceed particular pressure parameters. The limit switches on GM systems were inline with the compressor power wire and not related to engine temp at all.

CBODY67

 

[Davea Lux]

Otherwise known as a high pressure cut out. Under high RPM operation, such as a high speed pursuit, the reed valves in the RV2 compressor do not cycle properly. The compressor relies on returning refrigerant to cool it. When the reed valves lose the ability to open and close properly at High RMPs, the gas does not get compressed back into liquid and the refrigerant begins to super heat and brings no cooling back to the compressor. This is a self destructive process, the more the refrigerant temperature rises the harder it is to compress back into liquid and the more heat and pressure is generated. Eventually, the oil in the compressor can start to boil and be expelled out with the super heated refrigerant. The already overheated compressor starves for oil and either seizes or flies to pieces. In most cases the high limit switch would shut down the compressor before a catastrophic failure occurred when the preset high pressure limit was reached.

Dave

 

[CBODY67]

Otherwise known as a high pressure cut out. Under high RPM operation, such as a high speed pursuit, the reed valves in the RV2 compressor do not cycle properly. The compressor relies on returning refrigerant to cool it. When the reed valves lose the ability to open and close properly at High RMPs, the gas does not get compressed back into liquid and the refrigerant begins to super heat and brings no cooling back to the compressor. This is a self destructive process, the more the refrigerant temperature rises the harder it is to compress back into liquid and the more heat is generated. Eventually, the oil in the compressor can start to boil and be expelled out with the super heated refrigerant. The already overheated compressor starves for oil and either seizes or flies to pieces.

Dave

I knew that TX DPS put an a/c compressor shut-off switch on their '72 Furys, but I was always under the orientation that it was to cut the compressor off in high-speed chases to compensate for the lower power the '72s had compared to earlier models. Never did know about any compressor issues as you describe, so that's something new to me.

The thermal limiters on the GM systems always seemed a little suspect to me. Some years used them and the same car a year newer didn't. As if they were from, say '76 and older only? Maybe '75?

One way Chevy addressed the compressor speed deal was a larger pulley for the clutch. '77-'81 Z/28s and pickups from the late '60s had the larger clutch, as the vehicles had deeper gears. Cars, with highway gears, got the normal small clutch pulley.

Thanks for the info!
CBODY67