I want to use the 4th gen LTX high pressure sensor which should be the same or very similar to the LSX sensor. How do I physically bolt in this sensor? It will not go on the thirdgen high service male fitting. Is there an adaptor I can buy somewhere? No luck finding one.

Update 09/26/10 - 1987 or 1986 and below may use different fittings. Its possible the sensor will bolt in place where the thirdgen high pressure switch was on '88-'92 thirdgen line.

If the LT1 sensor can't be used, it may also be possible to fool the pcm with a little re-programing and wiring (or just wiring, resistors, and relays) and still use the PCM to control the a/c compressor. The advantage to being controlled by the LT1 pcm would be the pcm would send a signal to the idle air controller in the throttle body to increase RPM at idle so the engine doesn't kind of bog when a/c compressor cycles on/off. I'm working on a solution

 

I would email Hawks about the high pressure switch. The description on the LSX ac hose page says to use the 4th gen high pressure switch. The LT1 and the LSX switch should be very similar. I know the the hose block and hoses are.

http://www.hawksthirdgenparts.com/ls...passkit-1.aspx

 

if you are talking about the 3 wire pressure sensor you just need to get one off a r12 fwd system a 1990 pontiac grand am with a 2.3 vin a or d eng will have the correct one

 

Thanks. Advance Auto and RockAuto sell this part. Part number is AC delco 15-72104

 

Originally Posted by 88 350 tpi formula
if you are talking about the 3 wire pressure sensor you just need to get one off a r12 fwd system a 1990 pontiac grand am with a 2.3 vin a or d eng will have the correct one.


Will this switch also work in my '86 IROC that now has an '05 GTO (LS2) motor in? I am using the R134a freon. Thanks.

 

the switch should work fine but im not sure on the gto connector and also what and how you have the a/c system control setup.. all I know for sure is the 98-02 f-body setup will work with that sensor mounted to the thirdgen high side line

 

The 1990 Grand Am sensor (AC Delco part # 15-72104, GM part # 22599559) is also on the following vehicles in this link: http://parts-catalog.acdelco.com/cat...&parttype=2902

Found out the part costs about $50 new. I have attached a Word Document to this post that is one page long with the car/engine list and works nice when you are hunting for the part in a salvage yard. I found out its fastest to find the year of a car by looking at the factory stickers under the hood. Note that the part uses a 5/8" wrench to remove and NOT a 9/16 like the newer LSx/LTx sensor that looks very similar. You want the sensor that takes a 5/8" wrench to remove.
*

 

Were you ever able to locate an adaptor to run the 4thgen pressure sensor on the early 3rd gen line? Looks like you just used a different sensor. I already bought a new 4th gen sensor and pig tail so I'd like to find a way to use it.

 

What is the purpose of using the 4th gen switch?

 

Early AC systems were independent of any computer control. They instead used hi/low pressure switches to enable/cut power to the compressor clutch when the min/max pressure thresholds were passed. Newer systems use an entirely computer controlled clutch, but pressure is still a factor. These systems utilize a sensor for constant feedback to the PCM. 4th gen sensors fit the 3rd gen port in most cases and satisfy the feedback requirement

 

So the sensor your referring to plugs right into the 3rd Gen line with no modifications?

 

The 4th gen high pressure switch (3-wire) takes the place of the third gen switch (2-wire). Not all third gens used a high pressure switch. I think it's an early year/later year thing. I don't know where the year break is, but my '88 had it. I used the switch from my '02 donor car. When you remove the third gen switch, there's a schrader valve under it. Just unscrew one switch & screw on the other. I don't see why a later year high side line couldn't be used on early year cars that don't have the switch.

Image shows mine on the frame rail, kind of next to the oil filler.

 

Did you reuse alot of the original 3rd Gen wiring for the AC?

I'm been looking at the thread that someone posted showing a color drawing of their AC wiring setup but it looks like a lot of extra wires that would have to be ran to the PCM. I only have one A/C related wire on my stand alone harness that I bought which is for the A/C recognition signal input.

 

So it sounds like the best route is to have it controlled by the PCM to keep the car form possibly bogging down.

 

My system is all third gen except the fourth gen compressor using Hawks conversion hoses. The third gen hvac harness is retained. Connections for the compressor & high pressure switch were included in the conversion harness I bought from Hawks. There was one wire from the pcm that had to be spliced into the connection for the third gen cycling switch on the dryer. Having the pcm control the a/c is the way to go. It also commands my second fan to come on whenever the a/c is on.

 

Yes my fans are setup in the same manner to come on with the AC. I thought my extra wire was supposed to go to the light blue wire as an AC input signal. I still need to find out where the wires for the 4th Gen switch should go.

 

Sorry I can't be more help on what wires go where. My harness was pre-made, so I just plugged in the connectors that had mates & spliced the wires that did not, according to the instructions that came with it.

 

Do you still have the instructions?

Could you post some pictures of your engine bay around the AC connections? That would help me out a lot!

Aaron

 

Here are the pictures. The instructions, which were not very detailed, simply said to cut the light green wire on the cycling switch & splice in the dark green wire for the a/c input to the pcm. Pictures show the one wire spliced to the cycling switch, three wire connector for the high pressure switch & two wire connector for the compressor clutch.

I'll try to find the instruction & scan a copy...

 

That would be awesome!