vze2jshn

Recently replaced water pump, cam belt and engine harness ( '78,928) now temp gauge registers about 1/4 higher as operating temp (3/4 mark and a little above) then it used to AND when I put on blower fan for heat or fresh air, temp gauge jumps another 1/8 towards red section of temp gauge it also jumps the same way when electric fan comes on. Could I have wires crossed on temp sending unit -is that possible ? Anyone experienced this?

Mrmerlin

get an IR gun and test the temps going into the radiator they should be close to what the thermostat is.
you might try cleaning the contacts at the temp sensor use an eraser

Landseer

Then, I'd trace every wire in the harness and concentrate on cross-continuity checks during the process. What was the source of the new harness?

Go-carter

Perhaps voltage issues? My temp gauge jumps 1/8 up when I turn my lights on.

Mrmerlin

Ahh missed the new harness point try cleaning the 14 pin connector above the hot post and fit a hot post cover.
Cover is in the lower left hand corner of this picture

vze2jshn

Thanks. Hose without thermostat housing goes into the radiator, correct? When you say say temps should be close to thermostat do you mean 83 celsius or the real time temps at the thermostat hose? Harness was sourced through Carl Fausett at 928 motorsports. May be movement of temp gauge is normal and I am just noticing it now because gauge always starts reading now at 3/4 and a little above rather than the usual 1/2 and above in the past.

WallyP

Sounds like electrical/grounds issue. Most 928's could use some cleaning and refurbishing of the electrical connections.

Go-carter

Does anyone have a part number, or closer pictrue of this one? Couldn't find anyone on the net.

Ducman82

here it is just above the jump post.

Landseer

Building on Ducman's post, there is another picture on post #18 of this link.
Also, search feature is definitely your friend on this subject.


https://rennlist.com/forums/928-foru...-solved-2.html

vze2jshn

Have had plastic cover over 14 pin connector for years. Also replaced top part of connector with male connectors which came as part of Carl Fausett's engine wiring harness, but will check all elec. connections.
Still wondering about temp relationship between two radiator hoses.

Landseer

Fraggle posted a lot of data from his overheating problem. He used an infrared (IR) device to measure and record.

I'm generally seeing a delta T of 20 degF, but my equipment is not reliable.

fraggle

I see about 195F at the bridge and 155F coming out of the rad using my IR gun.

Mrmerlin

just so every one is on the same page the top radiator hose is the one thats the outlet for the thermostat,
so this will be the hottest coolant temps seen with your IR gun.
the return is the lower hose

vze2jshn

Thanks,thought so on the hoses but just wanted to check. Used IR gun and with temps at the thermostat housing reading 186-187F temp gauge is reading 3/4 and a little above. Temp difference between hoses is about 15F. Occasionally for a few seconds lower hose from radiator read a few degrees higher than the one from the thermostat--may be my not so precise use of the gun. Elec. fan goes on/ off at spec temps. I cleaned contacts for temp gauge sensor and fuse for left side of instument panel and the movement of temp gauge with blower on diminished greatly. I think this points to a temp gauge sensor that is faulty--reading 3/4 and higher with temps pretty much at or a little below normal operating temps. I will probably replace it. It is a bit unnerving to look at a temp gauge reading that high erroneously even though you know it is inaccurate. Thanks for the helpful suggestions. Any further comments are greatly appreciated. Greg Heinrichs.