I have a 1996 lt1 stock motor started the car to let it warm up warmed up normal digital gauage hit 230 no fans took out scan tool can get bolth fans to run high and low they work with ac on and car does not overheat on highway snapon scanner also showed 230 any ideas

 

A stock 92 has the following fan enable temps:

Fan 1 Low MPH - 219*F
Fan 1 High MPH - 228*F
Fan 2 Low MPH - 228*F
Fan 2 High MPH - 235*F

I imagine a 96 would have similar settings. Normally I would say that you're going by the analog gauge which isn't linear and thus not accurately read. If you told me that you were, in fact, looking at the digital gauge I would suggest that for some reason the computer isn't seeing the same temperature that it's reporting. You said, however, that the scanner also shows 230 degrees.

If you have access to them, I would look at the service manuals and start investigating the fan enable circuits. I would think that if you can command them to come on with the scanner, then there shouldn't be anything wrong with the circuit. It sounds like the PCM is simply never sending the command unless you force it to.

Can anybody verify the commanded fan temps for a 96? I know they were programmed to run very hot for emissions.

 

From the 96 service manual:

The PCM will command low speed fans ON at 104 C (219 F) and OFF at 98 C (207 F) and, high speed fans ON at 109 C (228 F) and OFF at 103 C (214 F).

The 1996 fans operate a little different than other years in that they are both either OFF, on Low, or on High.

 

Also, 230 is not really too hot. GM says to shut the car down when/if it reaches 260.

So, I would let it get a little hotter to see if they come on. Since you say they come on with the A/C, the fans themselves have to be ok.

I usually just leave the climate control set to auto, and can sit in traffic without any problems. Yes, the temps get into the 230-235 range at that time. But they have never gotten any hotter than that. And once you get moving over approx. 35 mph they come back down into the 195 range.

 

thanks for all the input i will let it get a little hotter to see if fans come on if they dont could it be the pcm

 

I think its possible, but the only way to know for sure is to run through all the diagnostic steps in the service manual.
There are 6 pages of them listed in the 96 service manual.

I do not really have the experience to give you much help, so I hope a more competent trouble shooting member can help.

You might consider purchasing the service manual though if you want to get the best results without throwing un-needed parts at it.

 

I have the fsm it seems to point to the pcm just was looking for something i might be missing

 

Ok, it sounds like you are ahead of me in trouble shooting ability then.

Book 2, page 6-639 lists all steps to troubleshoot (in case you haven't seen it yet).

 

got out fsm i do steps one threw seven it says system ok but fans dont come on at228 degrees

 

The gauges in these cars are not super accurate.....allow for a little variance.

 

I guess i will let it run a little hotter see if the fans come on thanks for all the replays you guys are the best

 

The 96 has 3 fan relays (mounted on the driver side of the radiator housing).

However, the PCM only has 2 circuits (throughout the LT1 years) to ground the 1st circuit (primary) at 228+/- F (albeit the FSM notes it should be 219 F for some years) and 2nd circuit (secondary) at 238+/- F.

The only difference with the 95/96 is the 3rd relay which helps routes the current either in series through both fan motors (slow speed - primary) or in parrallel (high speed - secondary).

Considering that the fans work via your scan tool, I would think that the relays and fan motors are fine.

The PCM activates the fans by grounding the fan relays. I doubt the PCM's logic circuit has failed, as I would doubt it uses two different logic circuits, one for normal fan operation and one when the scan tool/dignostic mode is enabled.

However, I have noticed on our 1994 LT1 that the A/C pressure can have an effect on the fan operations even with the A/C off (e.g. with freon pressure low, the secondary fan/circuit did not operate immediately or even after awhile, when the A/C was turned on -- regardless of temp, and seemed to not operate at the 338 F when the A/C was off -- however, after charging the system, the nearly immediate operation of the secondary fan resumed with the A/C on as well as kicking on closer to 338 F with the A/C off.

Therefore, how is your A/C system and it's freon pressure. Is it cold? Might you have (or be able to borrow) a set of A/C pressure gauges which you could use to check the freon charge?

You might also be able to use your Scan tool to read the A/C pressures and see if all is good.

Also, there are 2 A/C pressure switches -- one is a high pressure switch, which is tied into the compressor clutch circuit, the other (lower one) is the one which sends the PCM info about pressure. Might be worth also checking the wires to that sensor, just in case.

 

thanks never though about the ac it was cold out i will check it out this weekend thats what i like about this forum always new info