Going back to the original threads on my earlier question-
I think I am blind or something, but I cannot figure out where the thermo limiter/fuse is that Ken was describing. I think I am probably looking right at it and can't see the forest for the trees. All I see on top of the heater/A/C box is an female electrical connector that is plugged into a set of three prongs. The prongs are mounted on a plate that appears to be removeable. Is this assembly the thermo-limiter fuse? Or am I just not seeing it?

Thanks for your help!!!

|UPDATED|8/11/2004 1:53:07 PM (AZT)|/UPDATED|

final word on the thermo limiter saga. It appears that isn't one on a 1970. I did get the compressor working again-poor electrical connection. Thanks for everyone's help.

Sounds like you found it. A small black plate with three terminals. One of them goes to the compressor clutch. Look at the color code and wire size to see if it matches.

Mickey, Just a little friendly advice, if you plan to do most of the work on your own your car it might be a good idea to throw down 30 bucks or so and buy a GM Service manual for your year car, I have one for both the 69 and the 72, they also cover Impala, Nova, etc, I couldn't do the work that I have done on both cars without them, and of coarse also with the help of the people on this and other sites, when I compare both manuals the 68-72 vette is pertty much the same, I have a factory manual for everything I own and then some, if you decide to get one, make sure it's a GM Factory manual, aftemarket manuals don't tell you $&#!

Anips-
Good advice. I am beginning to accumulate the manuals. At this point I have an Assembly Manual and have electrical diagrams coming. I do not recall seeing GM service Manuals on E-Bay (that is where I find most of this kind of stuff. )I will look further. I had a 73 and replaced it with a 70 and there are definite differences in the two cars. i am still confused about the location of the limiter. It appears that it must be inside of the heater box on the firewall. There appear to be two access plates with electrical leads/prongs. One right on the top under the vaccuum actuator for the wiper door and one on the side between the heater box and the rigth front fender down by the blower. The one on top has four prongs and the on on the side has two. I have traced the green wire from the compressor clutch and it appears to go to the one on the side down by the fan. Does your manual give any info? They both appear to be accessed by removing two screws/bolts in a plate on the box.

Thanks for your help and advice!!!

the one on top of the evap-blower case is the is the blower resistor, the one on the side of the case by the blower motor is the ambient temp switch, on my 72 the thermo fuse ( limiter) is located right next to the blower relay, just hanging there, three spade connector with two green and one black wires and a black plastic box shaped fuse connected to it, if someone hasn't hacket up the wiring, if it were a snake it would have bitten you by now, the black wire in the thermo fuse harness goes to the superheat switch on the very rear of the compressor on mine, those two wires, green and black from the compressor go to the thermo fuse.

Mickey, I'am looking at both my 69 and 72 GM serv. manuals and looking at the wire diagrams and they are different,maybe we are sending you on a wild goose chase,the 69 diagram shows the green power wire from the comp. going to the ambient switch (is NOT a fuse) on the side of the case near the blower motor and out with a tan wire to the AC contol switch under the heater control panel,the 69 compressor doesn,t have a super heat switch,and the black compressor wire just grounds to the comp.housing, does that sound right, the 72 wires like I discribed in the past, so it looks like GM added the thermal limit fuse somewhere between 69 and 72 to protect the compressor in case of low freon, what year, I don't have a clue, I'll look around some more, HEY, anyone out there have a 70 with AC, do you have a thermal limiter fuse?.....I've been thinking, if you don't have thermal protection which it sounds like you don't, then your compressor can run with low freon meaning low amonts of oil going thru the system thus causing compressor damage thus causing blockage of metal filings at maybe the dryer or exspansion valve?....wiring sucks!

|UPDATED|8/12/2004 7:11:07 PM (AZT)|/UPDATED|

Here's the latest-

You are correct that the green wire from the compressor goes into the ambient switch you are describing on the side of the heater box. Black wire from the comp is grounded on the compressor mount. There are no wires on the rear of the compressor. It does not appear that there is a thermo limiter.

Doing some simple elctrical testing I have found that there is continuity across the ambient switch. (it must be a normally closed switch). Also, there is 12v power coming into the switch from the tan wire when the heater control is set to A/C. So, given that there is continuity across the switch, that means there is 12v power going to the compressor via the green wire. When I turn the heater control on and off you can see the 12v power go on and off (on the voltmeter) just like its supposed to. Unfortunately, it is not causing the compressor clutch to engage!!!!!
HOWEVER, if I hook up a 12v power supply (leads off of a spare battery) directly to the compressor, the clutch will engage!!!???

The new question is- why won't the 12v I am getting from the heater control, through the ambient switch, to the green wire, to the compressor, cause the clutch to engage??? Even though I am getting 12v to the compressor, is it possible that the amperage is too low? Ir probably takes a good jolt to engage the compressor.

Help me Obewon.
Mickey

Man,wish I had the answer, going to have some dinner, read the manual, come back later

looked through the manuals coundn't come up with anything, no simple trouble shoot on compressor clutch, the ambient switch is a evap. temp sensor, if the temp drops to 37 degrees the circuit opens killing the compressor so the evap doesn't freeze up,you said you had +12 at the tan wire, you had continuity at the ambient switch so you should have +12 at the compressor, now, are you taking this as a given, did you hook the voltmeter at the compressor end of the green wire,if not you might have a break somewhere in the green wire between the ambient switch and compressor