Jalisurr

Hey folks, hoping to draw on your wisdom in diagnosing this one.

I have a 1990 ZR-1. The air conditioning doesn't work. I've watched and the compressor isn't coming on at all. Here's what I've established so far:

-The HVAC controller is not flashing green, just steady.
-There are no codes stored in the HVAC. No code 9 for low freon or anything else.
-Jumping the low pressure switch doesn't make the compressor come on. I tried jumping it with a multimeter and there is current flowing through it, so I don't think it's anything upstream of that.
-The cooling fans do not come on when the AC is supposed to be on

Any suggestions? Unfortunately the A/C compressor on the ZR-1 is tucked under the intake plenum so I can't just jump it directly unless anybody knows where I could jump it farther back in the wiring harness.

Hoping to diagnose this issue more completely before I just start replacing stuff. So far all I'm somewhat confident about is that the system isn't just low on Freon.

Thanks in advance!

Jalisurr

Bump? Is C4 air conditioning truly a black hole?

81c3

I also have a 90 ZR-1 and the same symptoms as you. I havent gotten anyone to give any advice either....

Jalisurr

Well, misery loves company, I suppose.

With summer beginning in earnest I may just bite the bullet and take it into a professional. If I do I'll be sure to update you guys on what the problem was!

billschroeder5842

This is the best course of action. If you feel like spending, have them do a legit 134 conversion.

GREGGPENN

Without pulling out the manual/schematic, my next thought would go to the cabin temp sensor. I think it's in the halo behind your head. If it's reading "cold", I wonder if that could fail to set a code and prevent A/C operation? Sounds like you haven't put guages on it to confirm Freon level?

VikingTrad3r

I feel bad seeing a zr1 owner with no help!

I do not have a zr1 (though i really want one!!) but perhaps the clutch is toasted? can they seize and not engage even when commanded?

on the L98's i think there is a HIGH pressure switch which stops the compressor from engaging and maybe you have a similar that is malfunctioning?

Jalisurr

GreggPenn: I don't think it would be the cabin temp sensor as even when set to maximum cooling it doesn't engage, and my understanding was in that case it should be constantly running regardless of cabin temperature. I have not put gauges on it to confirm Freon level, but jumping the low pressure switch that should detect that doesn't make any difference, even though I'm seeing current flow through it.

VikingTrad3r: It's entirely possible the clutch is toasted. I'm really wishing there were an easy way to test it. If ANYBODY knows somewhere I can jump the compressor clutch without needing to remove the intake plenum so that I can test, that would be fantastic.
I don't think it's the high pressure switch as when I measured across the low pressure switch I was getting current flow and the high pressure switch is before it in series so it must be open.

PatternDayTrader

Unfortunately step one is get a pressure reading on the low side.

PatternDayTrader

Don't take this wrong, but what you are saying here doesn't really make any sense. You cannot jumper the low side switch with a multimeter. Not enough current will pass through it. You could try an ammeter, but really you should be using a jumper wire, so maybe give that a try and report back.

Jalisurr

Ah, yeah, totally true if it was a normal volt/ohm multimeter. Mine has an ammeter built in as well though, I was using that. I did try with a wire first, and when that did nothing I used the ammeter to confirm that current was flowing - I saw around 3A going through that switch.

PatternDayTrader

We need someone to post the wiring schematic.
I cant remember if the low pressure switch allows the clutch relay to close or if its in series with the clutch itself. If its in series with the clutch itself and you have 3 amps going through it then your next step is access the compressor and see why the clutch isn't engaging, because it should be.

65Z01

On my '88 clutch power goes from the Hvac controller through the AC Hi-pressure Cutout Sw (NC-opens at 430psi) then the Pressure Cycling Sw (NC-opens at 24.5psi, closes at 47psi) then through the AC Compressor Clutch and the parallel AC Clutch diode as well as back to the Hvac controller.

Jalisurr

So in that case, I should be able to assume that it's nothing before the Compressor or compressor clutch, as there is current flowing through the low pressure switch. Hmm

PatternDayTrader

That's a pretty safe assumption provided you are sure a few amps is moving through the circuit and not volts. A broken compressor shaft could do what you are saying. You might try jumping 12 volts at the switch with the key on engine off, and see if you can at least hear the clutch click as it engages.

81c3

Made an appointment to bring mine into the shop. They will check all the switches and such, then they will vacuum it down, refill with freon and dye. If the charge doesn't hold, then I can bring it back in and they should be able to find the leak via the dye...

Coupe89

With my Z. Its been the condenser 2x and evaporator 1x Since I've own it.
I'm on Using R-134a

raya123_2000

Try removing the battery power to reset the ECM, then see if the compressor turns on. If the system is low on Freon it will set an error in the ECM and turn it off period. I don't think shorting the low side works unless you power cycle the ECM first. Freon cost more to buy than converting to R-34.
I converted my 1990 L98 from Freon to R-34. you need to drain the system (I had the compressor rebuilt for a new front seal) flush all part, then a new dryer, new schrader values and a expansion Device (they come in different colors, the darker colors are for hotter area's) Figure out how many pound of R-34 you need, rent a pump to evacuate the system then put in R-34 until the systems air is around 60 degrees F. Get a thermometer for cooking works great.

billschroeder5842

This is your best course of action. AC is Voo Doo science and is very difficult if you don't have the proper equipment.

ChumpVette