OEM radio coax.

Steven Petersen · Jan 7, 2021

I have the factory am/fm with cassette/equalizer in my 88. AM reception is pretty good but FM very weak. No static or noise, just weak on FM. I checked ohms on the coax from the radio end to the antenna base. 1.5 ohms. Is that too much resistance? Bad coax?

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AK49BWL · Jan 7, 2021

The 88 CDMs were pretty weak from the beginning... The CDM is the metal box above the accelerator that everything plugs into. If you can get one from a 92+ truck (or some GM cars used them too), you'll find your reception will likely improve and your speaker outputs will definitely improve.

Steven Petersen · Jan 7, 2021

AK49BWL said:
The 88 CDMs were pretty weak from the beginning... The CDM is the metal box above the accelerator that everything plugs into. If you can get one from a 92+ truck (or some GM cars used them too), you'll find your reception will likely improve and your speaker outputs will definitely improve.

It could be since I’m comparing to my 2014 and 2018 GMC’s. Plus I’m in a pretty remote area with few stations.

I’m actually buying a 94 CDM from a guy on EBay that rebuilds them and adds Bluetooth and an aux jack. I guess the 94 CDM’s were a higher output unit. For now I just wanted to make sure I didn’t have a coax issue. Is 1.5 ohms resistance acceptable?

AK49BWL · Jan 7, 2021

That I'm not certain of actually. I'll check mine tonight and see what it says.

mars2878 · Jan 14, 2021

AK49BWL said:
That I'm not certain of actually. I'll check mine tonight and see what it says.

Any updates?

Steven Petersen · Jan 15, 2021

mars2878 said:
Any updates?

I don’t have an update on the coax. I did order another CDM from a guy on eBay that adds Bluetooth and an aux jack. I’ll report back on how it works out.

thinger2 · Jan 15, 2021

There is a pretty common problem where the antenna mount leaks water and that runs down through the seal all the way to the sterio and causes the coax connection to corrode.
If you install a new one, put a "drip loop" into it
Basically keep your coax lower than the plug or twist a loop into it so water drips off of the loop instead of running into the electronics
Check out the "plug in" at the radio.
You also should look at cylinder to firewall grounds and the hood to fender ground

Steven Petersen · Jan 16, 2021

thinger2 said:
There is a pretty common problem where the antenna mount leaks water and that runs down through the seal all the way to the sterio and causes the coax connection to corrode.
If you install a new one, put a "drip loop" into it
Basically keep your coax lower than the plug or twist a loop into it so water drips off of the loop instead of running into the electronics
Check out the "plug in" at the radio.
You also should look at cylinder to firewall grounds and the hood to fender ground

All grounds and antenna tip to radio tip of the coax are around 3.2 ohms. Since they're all very close, I think my ohm meter is slightly off. But I'm pretty sure the coax and ground are fine. Hopefully the other CDM has a stronger tuner.

OEM radio coax.

Steven Petersen

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AK49BWL

GMT400 Forever!

Steven Petersen

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AK49BWL

GMT400 Forever!

mars2878

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thinger2

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