No A/C when motor warm
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Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
No A/C when motor warm
Ok, '99 F450 has had a/c problem for couple years and finally getting around to fixing it(co. truck and enough people complained).
When dead cold, compressor will cycle quickly, like low on freon. Low side goes from 40 to 20 and back again as it cycles. Put a set of good gauges on it today and I can't get it to turn on at all. Even jumped both hi and lo switches.
Originally I was thinking it was the clutch, but when cold I was able to jump switches and make it run continuously. I didn't have gauges then and didn't want to burn it up so now I have gauges and it won't come on at all(when warm). Will have to wait a couple days til I can try it again when cold(like in the morning before it gets used).
Any thoughts?
When dead cold, compressor will cycle quickly, like low on freon. Low side goes from 40 to 20 and back again as it cycles. Put a set of good gauges on it today and I can't get it to turn on at all. Even jumped both hi and lo switches.
Originally I was thinking it was the clutch, but when cold I was able to jump switches and make it run continuously. I didn't have gauges then and didn't want to burn it up so now I have gauges and it won't come on at all(when warm). Will have to wait a couple days til I can try it again when cold(like in the morning before it gets used).
Any thoughts?
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
With the Low Pressure switch on the accumulator bypassed, tap the face of the compressor with a dowel or screwdriver handle. If it engages, the clutch gap is too wide and needs to be adjusted.
The gap gets wider as the engine heats up. That's why it will engage when cold, but not when hot. It's probably right on the edge of not being able to engage when warm.
Your previous short cycling probably indicates a leak and low system charge.
The gap gets wider as the engine heats up. That's why it will engage when cold, but not when hot. It's probably right on the edge of not being able to engage when warm.
Your previous short cycling probably indicates a leak and low system charge.
Junior User
Joined: Dec 2008
Posts: 52
Likes: 0
Isrx101 is rite on the nose with his suggestion abt the air gap he in structed me as how to repair mine and it is working like a charm,,, He saved me abt 200 bucks for I was just abt to order a new compressor ..I wonder how many ppl have had to pay thur the noise to have a compressor replaced and it cld have been repaired with a simple fix,,,I repaired mine in abt an hour,,thanks agn tom////
Elder User
Joined: Feb 2006
Posts: 592
Likes: 1
I just had a 99 F150 I did it to the other day. The guy was moving to TN and wanted it working. I whacked it and it took off. When I checked the refrigerant, it was way too high. I'm sure the previous owner(s) had been just adding refrigerant, thinking it must be low.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
I just had a 99 F150 I did it to the other day. The guy was moving to TN and wanted it working. I whacked it and it took off. When I checked the refrigerant, it was way too high. I'm sure the previous owner(s) had been just adding refrigerant, thinking it must be low.
Yep!! I've seen that a few times. When they can get it to run, just keep adding juice. It must be low on "freezon"....right?
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