I've got a 1999 chevy suburban 5.7L with approx 170K miles on the original engine. Forgive me, I am a female owner with limited knowledge. I can tell you what its doing and one year ago I did have to replace the fuel pump entirely.

Last year, my A/C went on the vehicle. I recharged it, and it worked for a while. This summer I noticed it was not working properly again and considering we've had a cold summer thus far in michigan I didn't really worry about it. The truck's stall issues had been resolved by replacing the fuel pump last year. Then, as would be the case for Michigan, the summer found us. A few days of mid to upper 80s and I started running the AC again. Sure enough, I had issues. Now, let me mention that I had to use cans of freon from the local auto store to recharge my AC to get any cool air to come out. Even then, it was haphazardly working. But at least while dressed fully for work, I was not dripping wet when I reported in. The very first time I ran the air, sure enough, while restarting the engine at the gas station, she refused to turn over. I got her to start, but as I pulled into the driveway at the office, she sputtered and wanted to stall. After a few hours of work, I returned to my truck, started her rightup, and she promptly idled and stalled again. I drove her home two footed that night not allowing her to idle down enough to stall. I didn't run the air again for another week, no need to really. Ran the air again due to hot weather, had to use more cans of freon to do so, and sure enough, stall issues, only this time, it was super hard to get her to finally turn over. Once I did, I let her sit for 8 hours at my friends house, turned her right over, and drove her home with out a single issue of stalling.

One thing that has me so puzzled is how in the heck does running the ac cause the fuel relay to be super hot. when I couldn't get my truck to start at my friend's that day, I popped the hood to just take a look at everything. The fuel relay was SUPER hot. I tapped it a few times and the truck turned over but I was too afraid to drive it at that point and let it sit that 8 hour stretch.

If i don't run my AC I have no stall issues with my truck which makes me wonder if this is not a fuel pump or related issue, but some connection between the heating/cooling system and that fuel relay.

I hope I've given someone enough information that a bell will ring in their head and I'll know what to do to fix this truck. I do have 3 children that rely on me and we live in the middle of nomad's land. To fix this truck, or rather, have a mechanic fix it and run a bill up trying to rule out this and that will financially ruin me and my children. Any help or advice would be appreciated. Thanks a MILLION in advance!

I'm afraid what sounds like happened to you is a good example of why people shouldn't be messing with their own A/C. You have been just arbitrarily adding more refrigerant without any idea if it was low to start with. These systems require a very specific amount of charge and if they are overfilled, it will cause the pressure to go sky high and just destroy the compressor and sometimes make it seize up. Obviously I can't tell you for sure that is your problem but it needs to be diagnosed properly. If you have ruined the compressor now, you probably added about $1000 to the repair. I understand your financial situation but what your doing is just making matters much worse.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Its pretty apparent that the ac is fried, and I readily admit that I'm looking at a costly repair. But the big question is, can this issue cause the stalling of the engine/fuel relay switch overheating? Is it connected or two separate coincidental issues?

The compressor can certainly cause stalling just by binding up and holding the belt back but the fuel pump relay wouldn't be related to that. The cause of that is going to be either poor contact at the relay plug itself or a fuel pump that's drawing excessive current.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Ok, thank you. Would it be advisable or possible until I can afford to repair the ac properly to somehow disconnect the compressor/ac system?

Just don't turn it on. You said it ran good if you didn't use the A/C, right?

Actually you may have to unplug the compressor because it will engage in defrost mode also.




78 Corvette Pace Car For Sale-18k mi orig-Florida

To add and sorry for the troubles. These are notorious for body leaks at compressor and recklessly blasting in more refrigerant is a death wish! If this has rear air in Michigan you could be looking at a $6000 repair now!

It's almost non A/C season so disable it is the suggestion. There's a Low Pressure cut Out Switch that if left disconnected would stop the stalling or the plug at the compressor OR a relay well marked underhood. Compressor can and will come on when it feels like it - even without requesting it and near always will with defrost request. Another GM "Mark of Excellence" (NOT) it can come on without any request!

If compressor fried it took more with it. If rear air it can be disabled and save a fortune if you want it to work again front only. It only has one compressor and so many BTUs of cooling so get a fan to move air to rear - ceiling mounted as rear is a nightmare!

A/C charge stuff should come with a well marked label that you are risking thousands if uniformed which they don't.



In the trade they are called "Death Kits!" -- would you have tried if warned? Sorry for the troubles - it's a common flaw in advertising products,

T
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Tom Greenleaf - MetroWest, Boston