This is topic AC help in forum Tech Talk at Northern California Ford Owners  .


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Posted by adower (Member # 5955) on :
 
Trying to diagnose my ac issues on my car. 98 cobra

I bought one of those cans of r134 with the gauge to check the psi. It was reading low at 20ish on the low side rail. I used the r134 and got it to 40psi. The ac still does not blow cold air. I am wondering how accurate are these gauges?

I’m also going to try and jump the ac cycling switch and look to see if the ac clutch engages. If it does then I believe I have a faulty switch? Any other ideas on what to look at?

I’ve been reading that it’s better to have the whole ac vacuumed then re filled versus using one of those cans but I’m not sure.

Any help is appreciated.

[ 2018-04-27, 09:08 AM: Message edited by: adower ]
 
Posted by KevinK (Member # 9234) on :
 
If you had pressure in the system then no need the evac the system. It’s a different story if you have a leak to fix.

The low pressure cut out switch disables the ac clutch power. Jumpering the switch should engage the compressor. When charging from the low pressure side, you often need to jumper the switch to keep the Freon flowing. If you watch the low side pressure, static will be much higher. Once the compressor engages, it will suck down the pressure. Somewhere about 25 psi, it will disengage until the pressure builds back up.
 
Posted by adower (Member # 5955) on :
 
quote:
Originally posted by KevinK:
If you had pressure in the system then no need the evac the system. It’s a different story if you have a leak to fix.

The low pressure cut out switch disables the ac clutch power. Jumpering the switch should engage the compressor. When charging from the low pressure side, you often need to jumper the switch to keep the Freon flowing. If you watch the low side pressure, static will be much higher. Once the compressor engages, it will suck down the pressure. Somewhere about 25 psi, it will disengage until the pressure builds back up.
I tried to jump the switch but couldn’t get the ac clutch to come on. Went out and bought a new switch but still had no luck. Any ideas?
 
Posted by 9165pt0 (Member # 7625) on :
 
The guage in the cans aren't the best way to diagnose ac system pressures. They can be hit or miss. You can actually rent ac manifold guage from autozone etc, they are more accurate and let u see both hi and low side pressures.

But as far the ac not cycling even when u jump across the switch, sounds as if there maybe a wiring issue. Have u tried to see if you are getting power to the ac relay? I'd start there
 
Posted by adower (Member # 5955) on :
 
quote:
Originally posted by 9165pt0:
The guage in the cans aren't the best way to diagnose ac system pressures. They can be hit or miss. You can actually rent ac manifold guage from autozone etc, they are more accurate and let u see both hi and low side pressures.

But as far the ac not cycling even when u jump across the switch, sounds as if there maybe a wiring issue. Have u tried to see if you are getting power to the ac relay? I'd start there
No I have not check that as of yet. I’ve been reading and there are some fuses that I need to check but I’ll also look into that. I appreciate the help. The relay you’re referring to is the one that’s in the wheel well? The ccmb?
 
Posted by 9165pt0 (Member # 7625) on :
 
I forgot about that I think you have to replace that unit as a whole. On your vehicle, id still check pressures with actual guages. But if you jumped the switch and the ac didn't cycle, your not getting power to the switch. This means we have to look at points before the switch. If you have ac fuses def check there first for an ez check, I forgot about the modules in wheel well in those, if have to check a diagram at work on Monday to double chk
 




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