TST, Lift Pump Replacement, and Air Conditioning

[mgonske]

Not sure if this belongs in Products/Accessories or in 3G 5. 9 Engine/Transmission



A quick search didn't turn up any posts on this, but TST's web site has an applicable FAQ entry.



I just had the dealer do the lift pump relocation mod on my '03 (after a LP failure). When I went to pick up the truck, the A/C didn't blow cold.



It sounded like the compressor was kicking in, but the dealer determined it was immediately kicking back out. I don't recall the trouble codes right now, but they determined the ECM was commanding the alternator to go full ("field?"), causing the compressor to trip off. They also had a code for the security key PIN not being recorded in the ECM (I wish I had written down those code numbers, or had my diagnostic manual handy to look them up). They were becoming convinced the ECM was bad, but tried a reflash (after disconnecting the TST, but leaving the EZ connected), and it worked. They tried a couple of cycles of connecting the TST, having the problem, disconnecting, clearing codes, and it working fine. They left it with the TST disconnected, and I was planning to call TST for advice (I'm interested in the upgrade flashes anyway). Ultimately, they only charged two hours labor for all of the original A/C troubleshooting, then the electrical troubleshooting, and then playing with the TST (I love my dealer).



I did some research on the TST web-site today in anticipation of calling them tomorrow, and found this in the FAQ:

When the PowerMax is turned on, the AC (Air Conditioning) shuts off/quits working.



-This sometimes occurs when a pusher fuel pump has been added (such as a FASS or a Air Dog fuel pump). Move the PMCR module ground from the battery terminal to inside the cab under the dash where there is a good ground. Don't leave it connected to the battery also, disconnect it from the battery and connect it only under the dash.

I don't recall seeing this on here before, but this might save someone else some troubleshooting time.

 

[JoshWelsh]

my 03. 5 truck ac has been acting up too. I dont know if it's my BD RAD or my TST like you said.

 

[cerberusiam]

It's a known "glitch" and there are several threads discussing it here.



Hope thats your problem.

 

[Tomeygun]

My A/C did just as said on TST's site. not cold with my new Fass pump. .



Sure enough, the ground on interior dash frame fixed it. Why? I dont care really. But it did !

 

[MMeier]

Hmmm, noticed that also on mine the other day. just had the LP relocate done last week after my original went out @ 161k miles.